Radio Boulevard
Western Historic Radio Museum
 

Vintage Longwave Receivers
Restoration and Performance Testing

Part 3  -  Post-WWII LW Receivers

16.  Signal Corps-Collins Radio Co. - R-389/URR

17. Mackay Radio & Telegraph Company - Type 3001-A

18.  Hammarlund Mfg. Co., Inc. - SP-600-VLF31

19.  RACAL Engineering Ltd. - RA-17C-12 with RA-237-B MW-LF-VLF Converter

20.  EDDYSTONE-Stratton & Co. Ltd.  -  Model 850/2
 

Other Write-ups:  Rycom R1307A/GR - Using Selective Level Meters as LW Receivers

Other MW/LF Receivers, Regen Rcvrs versus Superhet Rcvrs on LW, The Ultimate LW Receiver?

HAMMARLUND SP-600-VLF

The Best Vintage Tube-type LW Receiver?

PART 3 - Post-WWII LW Receivers

16.

U.S. Army Signal Corps

Collins Radio Company

R-389/URR
 

MW, LF, VLF  Double Conversion Superheterodyne

15kc to 1500kc

SN: 268  from 1951 Contract (1953 build date)

1953 R-389 SN: 268 installed in CY-979A Mobile Table Cabinet

Two RF amplifiers are used and the first conversion mixes the incoming RF signal frequency with the VFO (470kc to 1955kc output f) plus the 10.455mc Crystal Oscillator (8.5mc to 9.985mc resulting f) to achieve a 10mc IF. The second conversion mixes the 10mc IF with the same 10.455mc Crystal Oscillator to achieve the 455kc IF. This double conversion scheme was to allow complete coverage from 15kc to 1500kc with no gaps in the frequency coverage. Additionally, since the two mixer stages are 180 degrees out of phase, any drift within the conversion mixers is cancelled leaving only the VFO drift. This is similar to how the "drift-cancelling" Wadley Loop operates.

From the second mixer circuit on, the R-389 utilizes the same modules that are found in the R-390. That would be the six-stage IF module, the two channel audio and electronic voltage regulator circuit module and the power supply module. Although the 70H-1 PTO (VFO) looks similar to the one in the R-390, it's very different inside and tunes from 470kc to 977kc when the 15kc to 500kc range is selected. The VFO external output circuitry uses a 2x frequency multiplier producing a VFO output of 940kc to 1955kc when the 500kc to 1500kc range is selected.

The Veeder-Root counter is somewhat different than that used in the R-390 and provides two sets of digits, one for 15kc to 500kc (lower set) and the other for 500kc to 1500kc (upper set.) The resolution of the digits (tuned f) is to the tenth of a kilocycle (which are the red background digit wheels.) Neither a calibration oscillator or an antenna trimmer are provided (or needed.)

Most of the controls are the same as those found on the R-390. The BFO controls, the Noise Limiter, the Local Gain, Line Gain, Line meter range switch, RF Gain, AGC switch, Break-in switch, Audio Response switch and Function switch. The controls that are unique to the R-389 are Motor Drive, IF Bandwidth (five ranges instead of six,) RF bandwidth KC indicator and the single tuning knob. The two meters perform the same functions as the R-390 meters, that is, Carrier Level and Line Level.

Two antenna connectors are available. Balanced input for 125 ohms input impedance from dipoles or other balanced antennae. Balanced is connected to the primary winding of each antenna coil. Unbalanced input is for random length wire antennae. This input is capacitively-coupled through a .01uf capacitor to the RF amplifier coils. The Unbalanced input impedance is not specified but is probably fairly high assuming that end-fed wires were probably the design target Z. The Balanced input utilizes a "Twin-ax" two-pin coaxial connector and the Unbalanced input utilizes a "C-type" coaxial connector. As mentioned, no antenna trimmer is provided so the antenna impedance should be somewhat matched to the particular antenna input used.

Both audio outputs, Local Audio and Line Audio, are 600 Z ohm outputs and can provide about 500mW on Local and about 10mW on Line. The phone jack doesn't disconnect the audio output (LOCAL) from its respective load. There is a series resistor and a load resistor to the PHONES jack to keep the audio level (5mW) from over-driving the headset if the proper 600 Z phones are used.   >>>
 

photo right: Top of the R-389 showing the RF module and IF module mounted in the receiver. The RF module has the slug racks located under the cover. The two tubes showing thru the opening are the two RF amplifiers. The Crystal Oscillator and first mixer is the to the left and the second mixer is to the right. The IF module is to the left side of the main frame.

Unlike most other LF and VLF receivers, the R-389 doesn't have any fixed-circuit audio restrictions within the audio module other than the switch-selected Broad-Medium-Narrow. Selecting Broad results in a fairly wide audio bandwidth. Medium is shaped for voice with noisy conditions and Narrow is a bandpass filter at 800hz for CW. The IF bandwidth can be restricted down to 100hz. Both 100hz and 1000hz IF bandwidths use a crystal filter that's onboard the IF module. The 2kc, 4kc and 8kc IF bandwidths are determined by the IF transformers and Q-resistor set-up. For static bursts and other types of atmospheric noise, the dual positive-negative noise limiter is available. When tuning in the AM BC range, the receiver's bandwidth can be increased to 8kc and BROAD and, with no other specific audio restrictions, the resulting audio isn't too bad. However, the audio is more-or-less communications-grade audio so don't expect high fidelity because it isn't. Most listening on LW will usually be using a headset. Most listening on the AM-BC band will be on loudspeaker.

The R-389 is a "top notch" MW, LF and VLF receiver but using it today can result in user frustration due the very high noise levels that plague LF enthusiasts in many locations. The R-389 does cope with significant noise levels very well. It can do a good job with a wire antenna (probably what it was designed for anyway) especially if the user is located in a RFI-quiet area. Using a shielded magnetic loop antenna may help in extremely noisy areas but I've always had better reception using a large wire antenna. Of course, like any LW receiver, best results will be experienced when listening "at night" during the "LW Season" (Oct thru Mar.)

photo right: Bottom of the R-389 showing the Power Supply module on top, the VFO in the center and the Audio and Electronic Voltage Regulator module on the bottom. Motor drive system is directly behind the front panel. The long rectifier (green with fins) is part of the motor-drive tuning power supply. The long bent metal arm directly behind the tuning knob is the motor-drive clutch actuation arm that is cam-driven from the MOTOR TUNE control. The three coaxial cables behind the VFO are from the Antenna Relay box and are routed to the RF Module.

R-389 Restoration Log (Started March 11, 2018)

This probably isn't really a "restoration" but more of a full and complete "servicing" of the R-389. Includes the removal of any "non-military" modifications in order to return the circuit to the original design. Before starting it's worth noting that the receiver does function - not to spec, but it does receive some signals. This indicates that most circuits are working but probably not aligned where needed. The R-389 is a very mechanical type of receiver and this servicing will probably include not only electronic alignments but also mechanical alignments.

The R-389 Restoration Log has been expanded upon and that version can be found in the "R-389 Section" of "Rebuilding the R-390A Receivers - Part 4"

photo above: Under the RF module after cleaning off all of the grease. Note the two line shafts that drive the gears that turn the threaded shafts that raise and lower the nine slug racks. The motor-drive bandswitch is in the center of the chassis with the gear drive at the very rear of the module. The motor for the motor-drive tuning is in the lower right of the photo. Note the date on the motor - Sep 10 53.

March 18, 2018 - Dismounted Antenna Relay Box and removed bottom plate. I could see that the Balanced Input wiring had been changed from original. The mod has the Bal. Ant. connector wired to go to the output BNC connectors IF the receiver is turned off. When the receiver is turned on, then the Bal. Ant. input is connected to chassis ground. The reason for this mod seems to be prevention of using the Bal. Ant. input. Check April 4th for correction.

March 19, 2018 - Mod to B+ fuse and HV winding CT found. This mod removed the wires from the B+ fuse holder and soldered them together to eliminate the fuse in that circuit. Then the power transformer CT (pin  6) was disconnected from chassis ground in the power supply module and a wire routed from the CT to pin 15 (unused in ps) of J-118. This pin 15 P-118 connection was originally to the DC 20A fuse but was now routed to the B+ fuse holder and then to chassis-ground (on the Local Audio ground terminal.) This mod may have been installed because of the power supply module conversion to solid state rectifiers. It's likely that the "instant on" HV to the electronic regulator circuit tended to blow the 3/8 Amp B+ fuse. With the mod, fuse blowing would be at the power transformer HV winding current draw rather than at the output of the HV rectifiers to the input to the voltage regulator circuit. The mod also changed the fuse to 3/4 Amp.

March 20 - April 3, 2018 - I had to set aside the R-389 project temporarily. A Collins 32V-3 was acquired that needed testing, servicing and clean-up. I'll get back to the R-389 when the V-3 is completed (a few days, hopefully.)

April 4, 2018 - Well, two weeks (two other projects in addition to the V-3) and back to the R-389. De-mod'd the Power Supply by removing wire CT to pin 15 J-118. Reinstalled the correct bare 14 gauge, "tinned-copper" (TC) wire from chassis to both CT pins on power transformer as original. This completed the Power Supply.

Correction - Checked the Antenna Relay Box again and found that it is correct and original. The relay contacts are actually for grounding the antenna inputs when Break-In is actuated.

photo above: The gearbox after cleaning out all of the dried grease. The tuning knob has a built-in slip-clutch that's adjusted by the four recessed screws in the flutes of the knob (two screws are visible in the photo.) Behind the knob is the motor-drive clutch that is engaged when the motor drive switch is turned. This pushes down the lever which pivots against the adjustable standoff to the right and presses the clutch in which then drives the gears for motor tuning. Manual tuning is accomplished with the tuning knob and runs the gear train if the motor drive clutch is disengaged (that is, receiver not in "motor drive.") The tuning knob does "spin" while motor drive tuning.

April 6, 2018 - Removed all wires from non-original connections. Cleaned, straightened and re-tinned all lead ends. Installed DC 20A fuse holder and connected and soldered original wires. Re-wired B+ fuse to now have the original connection to the HV rectifier output. Cleaned all "mod writing" off of the back panel using WD-40 and "Goof-Off." This completed mod removal on the Main Frame.

April 15, 2018 - Back to the R-389. I double-checked some of the RF module mechanical alignments just to verify that everything was correct. Cleaned up some residual grease and splatter that I'd missed earlier. Cleaned the Main Frame bedplate. Cleaned the Veeder-Root counter and repainted the decimal point. Reinstalled the RF module into the Main Frame. This has to be carefully done because there are four cables that have to be routed through holes in the bedplate as the module is lowered into place. The position of the module has to be slightly moved so that the three bedplate captive screws thread in along with the two side screws and the one rear screw. When all six screws have been partially threaded into their pem-nut receptacles then all of the screws can be tightened. Don't over-tighten. Just snug is enough.

Mounted the front panel. The only unusual item to remember to install is the spring-loaded shaft that couples the Frequency Range switch to the mechanism that operates the dial mask. There is a steel brace that screws between the bottom of the RF module at the gearbox to the Main Frame that has to be installed. There are eight 10-32 FH screws that mount the front panel to the Main Frame that have to be installed. The motor drive power cable has to be plugged in. The two harness connectors have to be plugged into the RF module. The three antenna coax cables that come from the RF module and are routed through the Main Frame have to be plugged into the Antenna Relay Box. The remaining coaxial cable connects to the VFO.

I noticed that several of the knobs were the incorrect size for where they were installed based on the panel nomenclature size. I referenced the manual artwork and the manual front panel drawing to install the correct size knobs in their proper locations. Went to my R-390A spare knobs box to find nice condition replacements as needed.   

I found a correct style, good condition Line Level meter on eBay. This was cleaned up and installed. Apparently, when the original R-389 meters were removed the meters were "chopped" out with a cold chisel. On both meters, three of the mounting screw holes had paint scraped off however one hole on each meter mounting was severely "gouged" with a huge aluminum burr that prevented the meter from setting flush against the panel. I used masking tape to protect the panel and then used a file to remove the gouge's deformed metal to allow the meters to mount correctly. Once the Line Level meter was installed, the wires were soldered to the terminals. NOTE: It's odd that the original meters would have been removed for radiation since the original R-389 meters didn't have radium coated needles or scales.

More grease! This time on the VFO front gear driven switch. Also the oldham coupler was all greased up. The only reason for the grease on the oldham coupler is to hold it in place while installing the VFO. Only a very small dab is necessary on one side only. Once the greasy mess was cleaned up, the VFO was installed. I had set the frequency to 780kc (no particular reason but it's easy to remember - KOH's freq) so, since the VFO position wasn't moved and the RF module was set to 780kc, then the oldham coupler was in the correct position to allow the VFO to mount easily. The VFO is mounted with five captive screws. (I later had to actually synchronize the VFO for the correct output frequency of 470kc at 15.0kc.)

Installed the Audio Module and installed the Power Supply Module.

There was a brass blade screw used on the front panel to mount one of the resistor boards. Replaced this screw with the correct stainless steel flat head Philips screw.

Cleaned IF module as it seemed to have a light coating of oily dirt on it. Installed IF module and connected the three coaxial cables and the power input plug.

The R-389 was now ready for power-up, testing and electronic alignment.

photo left: The RF module with the cover removed. The two tubes between the slug racks are the RF amplifiers. Note the motor-driven bandswitch behind the tubes. The two left-most slug racks tune the VFO and Mixer Output Stages and Output Coupler. The remaining seven slug racks tune the bands 15kc-27kc, 27kc-56kc, 56kc-128kc, 128kc-255kc, 255kc-500kc, 500kc-855kc, 855kc-1500kc. Below the slug racks are the 34 RF transformers. Four for each band (28,) four for the output coupler and two for the VFO-Mixer output. Note the threaded rods that lift the various slug racks and the associated return springs (visible in the foreground openings.) The threaded rods are gear-driven by the two line shafts that are below the RF module chassis.

April 18, 2018 - Ran the R-389 for a couple of hours. I'm sure this receiver was rarely operated by its former owner. It was in a small storage room located under the house when I picked it up. I believe that getting some "hours" on it will help reveal any latent problems and should result in a better alignment.

April 19, 2018 - Aligned the IF module. 455kc IF transformers slightly off. Gained about 1 vdc on Diode Load after 455kc IF transformer adjustment. Crystal Filter off quite a bit, especially the core adjust that equalizes the output on the .1kc and 1kc positions. AGC adjustment off quite a bit. About one full turn of the adjustment to attain maximum AGC voltage. Ended up with increase of +10db on CL meter.  >>>

April 20, 2018 - Aligned First Mixer Output Transformer, Second Mixer Output Transformer and the 10,455kc Crystal Oscillator. This entire section of the receiver was out of alignment. The Crystal Oscillator requires using a VTVM to read maximum RF voltage. One adjustment is accessed from under the receiver and the RF Module brace has to be removed (just two screws.) This adjustment was quite a bit out from peak. The secondary (top side adjustment) was severely out from peak. These adjustments resulted in another +10db increase in signal level on the CL meter. The next step is to align all of the slugs and trimmers for the seven bands that cover from 15kc up to 1500kc.

April 23, 2018 - Adjusted R-260. This adjusts the balance on the First Mixer with one signal from the 2nd RF amplifier and the other signal from the Mixer Driver (VFO plus other stages.) This adjustment was off causing about a 2 volt increase over the minimum setting. Reduces Mixer noise.

The next test was to check the remotely tuned loop antenna operating with the R-389. When first acquired this R-389 didn't receive any signals using the loop antenna. I now connected the loop to the Balanced Antenna input and tuned to 314kc which is the frequency of a nearby DGPS node (read - "very strong signal.") The DGPS signal was received and could be tuned with the variable bias control on the loop. I noticed a significant improvement when the shield of the remote tuner was grounded to the receiver chassis. I also used the HP 606B RF signal generator (connected to a small antenna) as a signal source that could be tuned. This verified that the remote loop could be "peaked" or "tuned" to various received frequencies and that the Q of the antenna was fairly sharp. The higher Q with a sharp peak will give good signal strength with low noise since the antenna is only responding to a very narrow tuned frequency.

For more details on the R-389 performance testing, VFO end point error adjustments and other alignments go the the expanded version of this write up in the "Rebuilding the R-390A - Part 4" in the R-389 section. Use Home/Index below to navigate.

September 24, 2018 - Finally the Autumnal Equinox has arrived and conditions on LW, especially in the early mornings are improving dramatically. All summer-long, I'd perform tests on the R-389 trying various LW signals using combinations of antennae from loops to wires. Barely any signals were audible. Once in a while, the carrier of MOG 402kc in Montegue, California could be heard but usually the MCW was not audible. At night, the static crashes and other atmospherics seemed to mask all of the LW signals except for the DGPS nodes which were about the only thing that assured me the R-389 was at least receiving some types of LW signals.

With the Autumnal Equinox approaching, I began by listening in the early evening on 9/21/18, which was the day before the Equinox. Only two NDBs were heard, MOG and ULS (392kc, Ulysses, KS) and the noise was still pretty severe. I decided that in the next couple of days I would have to try early morning to see if the noise was down and maybe the signals would be up.

At 0530 on 9/24/18 I started listening using the 100'x135' "T" antenna. Right off, I tuned in ZZP 248kc from Queen Charlotte Islands, BC. Multiple NBDs were heard on many frequencies. I tuned around 390kc and heard what sounded like a voice transmission. I widened the bandwidth to 4kc (from 2kc) and at 394kc I easily copied voice weather being transmitted. With BFO turned off, I could hear in the background RWO being sent in MCW. This was the NDB on Kodiak Island that transmits TWEB or Voice Weather. In about 30 minutes of listening, I had tuned in about 30 NDBs, three of which were newly heard NDBs, ZZP 248kc, RWO 394kc and POY 344kc (#328, #329 and #330, respectively.)

I guess this illustrates that besides a quiet location, a large antenna and a superb receiver, good receiving conditions are absolutely necessary for successful LW DX copy and that my concerns about the R-389's abilities to cope with the modern LW reception issues were unfounded. As conditions continue to improve, I'm looking forward to the "peak LW reception" which will be from mid-November thru mid-January.

R-389 UPDATE: Oct. 1, 2018 - Tuned in LLD 353kc in Hawaii at 0545 this morning using 100'x135' "T" wire antenna. Also, tuned in JJY on 40kc, pulse-encoded time signal from Japan at 0615.

R-389 UPDATE: Oct 18, 2018 - LW conditions are just getting better and better. 50 stations tuned in about 45 minutes starting about 05:30. DB 341kc Burwash Landing, Yukon, CAN, FS 375kc Ft. Simpson, NWT, CAN along with ZF 356kc Yellowknife, NWT and MM 388kc Ft. McMurray, AB were some of the Canadian NDBs. LLD 353kc Lenai City, HI is a regular every morning. I'm finding that the R-389 maintains excellent sensitivity even with the Bandwidth set to 100 cycles (.1kc.) Using the 100'x135' "T" wire antenna.

R-389 UPDATE: Nov 13, 2018 - Listening evenings now that we're back on Standard Time. YY 340kc Mont Joli, QC, Canada, YXL 346kc Sioux Lookout, ON, Canada, IN 353kc International Falls, MN were some of the NDBs heard around 19:30 PST. Also heard MA 326kc Midland, TX which isn't that far away but it's on the same frequency as Canadian powerhouse DC 326kc Princeton, BC, Canada. Also, I'm noticing that I can easily tune in NDB stations between the DGPS nodes located from 285kc up to 325kc in the West. All listening was with the bandwidth set to 100 cycles. Still using the 100'x135' "T" wire antenna as the noise isn't too bad and signals seem very strong using the wire antenna.

UPDATE: Sept 27, 2019 - Tested new VFO set up with R-389 performance. Listened at 0505hrs to 0545hrs tuning from 300kc up to 410kc. Logged 45 NDBs. Two newly heard Alaska NDBs, JNR 382kc and EEF 391kc. Also, copied both Hawaii NDBs, POA and LLD. Alaskan RWO TWEB Voice WX on 394kc. DB 341kc at Burwash Landing, Yukon. It's a little difficult to remember to subtract about 6kc from the dial readout for the actual frequency but otherwise the R-389 is performing very well. Sept 30, 2019 - 0510 to 0545 hrs, logged 30 stations, two newly heard, X2 328kc at Athabasca, AB and PR 218kc at Price Rupert, BC.

UPDATE: Dec 2, 2019 - I had recently bought a used Pixel Loop antenna that was providing excellent results with some of the LW receivers I tested it with. When I connected the Pixel Loop to the R-389, I didn't hear much of anything. Then, around 356kc I heard a "not so strong" carrier. Expecting to hear NY 350kc, I was surprised that the NDB was actually DC 326kc and that the R-389 was once again 25kc off due to the erratic VFO problem. When the VFO is accurately tracking as it should, the R-389 is a great performer BUT trying to keep the VFO on frequency seems to be impossible. I'm convinced that the ferrite core has some kind of problem. I strongly suspect that the continuous operation of the oven every time the receiver was in use, possibly for decades, has taken its toll on the ferrite core.

NOTE: From the minute I got this R-389 refurbished and calibrated it's been plagued with an intermittent VFO problem. The VFO will "jump" in frequency about 25kc. Then the receiver is recalibrated for that new VFO frequency and operation is fine for a few weeks, then the jump occurs again to a new and different VFO frequency. When I got this receiver, one of the things mentioned was that the receiver didn't operate very well until it had "warmed up" for 20 minutes, then there was a sudden change and the calibration was "right on" and operation fairly normal. Once I started investigating, I found that the VFO oven was turned on and I thought the heat brought about the F change. I thought that with the oven off the temp would never go high enough for the change, so recal'ing the VFO with the oven off should cure the 20 minute wait-problem. It did seem to work but about every few weeks to a month or so, the F-jump happens requiring a re-cal (not difficult but it does require VFO removal.) My thoughts are that the long-term oven-ON heat has some how changed the ferrite material (minute cracks?) The capacitors in the VFO aren't of a high enough value to cause a 25kc change, even if they were removed (about 280pf is required.) I've been through this VFO several times and have done the recal at least four times. July 23, 2021  

ANOTHER NOTE: June 29, 2022 - I must be a real masochist - I put the R-389 back on the bench. But, to my surprise, it was back in calibration. I didn't do anything but have it in storage for 2 years. This is the first time that the frequency jump on the VFO has "healed itself" - even though I never waited more than a day or two on the prior "jumps." More and more it appears the problem is mechanical in nature. A cracked ferrite core or possibly it could be something as simple as a cracked solder joint. But, the first test is to see how long the receiver stays "in calibration" this time.

More details as things progress,...

July 9, 2022 and the R-389 is still on frequency. Tested everyday, no jumps yet. I continued this testing until Aug 31st and the R-389 remained "on frequency." Tested on Sept 25th - OK, still on frequency,...I'm sure it will change sometime in the future - and I was right - happened on Nov 2nd.

As part of the 2022-23 Longwave Season change to logging NDBs to specific receivers used rather than trying to increase the total of "newly heard" NDBs the following are some of the stations heard using the Collins R-389 this season. The R-389 is a great LW receiver when it's working correctly and I have had that operating pleasure,...once in a while,...but one never knows when things will go awry. And,...a sure way to instigate trouble is to start using the R-389 regularly. So, the following are some logs of NDBs (and other LW signals) copied using the R-389 with the 135' x 90' "T" wire antenna (until things finally do go awry.)

Oct 7, 2022  0535hrs-0615hrs

JJY 40kc Mt. Otakadayo, Japan 50kw PE Time

LGD 296kc La Grande, OR
DC 326kc Princeton, BC, CAN
RYN 338kc Tucson, AZ
POY 342kc Powell, WY
XX 344kc Abbottsford, BC, CAN
AL 353kc Trina, WA
MEF 356kc Medford. OR
YAZ 359kc Tofino, Van Is, BC, CAN
RPX 362kc Roundup, MT
SX 367kc Cranbrook, BC, CAN
YWB 389kc West Bank, BC, CAN
PNA 392kc Pinedale, WY
MOG 404kc Montegue, CA
MW 408kc Moses Lake, WA
LYI 414kc Libby, MT

135'x90' "T" Wire Antenna. Cndx good. Also, a carrier heard on 630M but no ID

Nov 2, 2022  1430hrs

I knew all I'd have to do is to start a log on the R-389 and that would instigate the VFO frequency jump. The measured jump is about the same as it has always been with KKOH 780kc tuned in on 824kc or a 44kc jump and extrapolated for the low frequency, that would be about a 22kc jump.

Nov 3 - An interesting experiment,...I turned the receiver on its side to have access to the VFO. I used a heat gun to warm up the VFO. After a minute or two, no change. I then turned on the oven. After about two minutes, the frequency suddenly changed and with tuning down to 780kc, there was KKOH. So, more testing will be required to see if this happens every time.

Nov 4 - Cold start and off frequency. Turned on oven and within five minutes jumped to correct frequency.

July 3, 2024 - CV-979 cabinet and some Testing

I was given a CV-979 cabinet that had been left outside for several years. It was faded and the paint a little oxidized. It was a Barker & Williamson contract. It had 3/4" thick wooden skids bolted to the standard steel skids. The wood was rough due to the exposure outdoors. Now, being outside in some areas of the country could be devastating but this CV-979 had spent its years outside under a carport in Yerington, Nevada. So the actual condition wasn't too bad, just faded a bit. I removed the wooden skids and then cleaned and waxed the cabinet finish. It turned out fairly nice. I've installed the R-389 into this CV-979 cabinet.

Since I had the R-389 ready to go, I did a little test. First test had the VFO oven turned ON. The receiver came up on frequency and was working quite well. About 15 minutes into the session and the frequency of the VFO jumped about 35kc (on Range 500-1500.) I turned off the receiver and switched off the oven. Later in the afternoon, I powered up the R-389 again. It came up on frequency and was working fine. I listened for about ten minutes and the frequency "jump" didn't happen. The next test will be to time how long the receiver VFO can operate with the oven off before the frequency "jump" does occur.

NOTE: Tested several times and the R-389 is still "on frequency." I've come to the conclusion that I can use the R-389 during the summer with no problems. During the winter (cold upstairs) I can get the R-389 "on frequency" by turning on the oven for about five minutes, get the VFO to "jump" and then turn off the oven. This will probably be the procedure I use until I find another R-389 VFO (yeah, I know,...good luck on that one!)

17.

Mackay Radio & Telegraph Company

  Marine Radio Receiver  Type 3001-A

Commercial MW, LF & VLF Shipboard Receiver from 1952

15kc  to  635kc 

SN: 52-M-070

TRF Stage, Regenerative Amp-Det, Audio Stage

The 3001-A has its original design basics dating from around 1940 with Type 128 Series of Mackay shipboard receivers but this receiver was designed around 1948 and the example shown was built in 1952. The Type 3001-A is significantly updated from the earlier Type 128 and, although many parts are very similar (or even identical) to the earlier receivers, the circuit was substantially changed for better adaptability for commercial shipboard (non-military) use. The Type 3001-A could be set up as the main receiver or as the emergency receiver depending on the ship's requirements. Usually these receivers were installed into Mackay MRU-19/20 shipboard radio console where two 3001-A receivers were used along with HF receivers, HF and LF transmitters and other auxiliary equipment. The 3001-As were panel mounted when installed in the MRU set-ups.

The 3001-A is a regenerative receiver covering 15kc to 635kc in four bands that uses an AC-DC circuit and can operate on 115vac or on DC using batteries. When BATT. is selected, the tube heaters are connected in parallel and a plug-in WW resistor is selected for the desired battery voltage with 6vdc, 12vdc and 24vdc being the most popular options. B+ was supplied by standard dry cell B batteries when DC operation was used. When LINE is selected, the tube heaters are then connected in a series string that includes a four pin Amperite ballast tube (along with the six octal tubes and two dial lamp loads.) An additional tube heater series load is provided by what appear to be dial lamps (they were for dial illumination in the earlier WWII versions) but these lamps are just acting as an additional load since the white dial is an opaque material on the Type 3001-A. A single TRF amplifier (6SK7) is used along with a "regeneration" tube (6J5) that amplifies the tickler coil response in the RF section to improve the feedback level. The regeneration tube's output goes to a detector tube (6SJ7) followed by a first AF amplifier (6SJ7) and then an audio output tube (6G6G.) The cabinet has "knock-outs" all along the back and the bottom-rear to allow routing the various cables necessary for the installation. These would consist of the Main Antenna and Emergency Antenna, the AC power connections, the DC power connections and an external earphone connection. A small built-in speaker provides for radio room monitoring but earphones would normally have been used by the shipboard radio operator.

The 3001-A receiver power is quite different from the earlier 128-AY (or RC-123 above) in that it's a true AC-DC receiver that has a series tube heater string (in LINE op) and a floating B- with the only connections to chassis being the cable shields and B- to chassis coupling capacitors. Although the receiver can be operated directly on a modern AC line (grounded Neutral,) if the AC plug is not polarized, then one does have to be careful that no other grounded equipment is connected to the receiver during testing or measuring (all voltage measurements have to be referenced to B- not chassis.) A 1:1 isolation transformer or a properly oriented (polarized) AC plug can be used to assure that the receiver circuitry is not inadvertently grounded.

These type of Mackay receivers were used onboard ship for decades (there are many reports from the 1990s that the 128 series Mackay receivers were still being used on some ships and a few reports indicate that some may still be in use.)

photo right: The under side of the chassis showing the various coils and other components. This receiver was partially re-capped sometime in the past. There's a combination of dark pink molded paper caps and some mylar dielectric caps. Also, the can electrolytic capacitor has been removed and a pair of tubular electrolytic caps mounted under the chassis. The large cardboard unit on the left side is the original dual section 8uf paper dielectric filter capacitor.

NOTE: The Type 3001-A sn:52-M-072 shown has a perf-metal grille over the panel speaker. This isn't original. The original speaker grille was a black felt-flocked, wire-mesh grille. The original grille on this receiver was missing most of its flocking and looked terrible. I had a piece of black felt installed and that looked just as bad. I then found this perf-metal grille and it was a perfect fit. It looks a lot better than the original grille but,...it isn't original. Also, the shock feet are not the original style used. These feet are from some piece of military gear I was parting out. They fit nicely and looked great,...however, they aren't the original type used with the Type 3001-A.

18.

Hammarlund Manufacturing Company, Inc.

SP-600-VLF31

 
 MW, LF & VLF Superheterodyne Receiver
Single Conversion with Double Preselection 

10kc  to  540kc

SN: 20101    from 1958

The 1950s was a time when the radio frequency spectrum below 500kc was brimming with signals that included many voice transmissions and lots of true CW transmissions. Signals that could be tuned included airport beacons (many TWEB NDBs with voice weather reports,) maritime weather and navigation signals, ship to ship traffic, ship to shore traffic, long wave AM broadcasting from foreign lands to name just a few. Nothing like today's almost entirely data-driven transmissions that defy decoding, unidentifiable signals of all varieties, rampant RFI (that always seems to be on the increase) and the rapidly diminishing and displaced airport beacons (Non-Direction Beacons or NDBs.) In the 1950s, the SP-600-VLF31 would have been used in the laboratory, in commercial coastal stations or perhaps onboard ship. It was an expensive receiver that probably wouldn't have interested the average radio amateur or average radio listener. It was mainly for laboratory and commercial or military users.

Discovered later that the spots on the chassis easily were removed using WD-40 (see 2024 photo further down.)

Note on this VLF receiver that a top cover is missing. It appears that the cover was a right-angle bent aluminum sheet metal piece that would engage into the front "pinching" two-piece retaining slot and then, resting on top of the side panels angled lip edges, drop over the side panels vertical lip edges. At the vertical rear panel, screws were used to mount the top cover to the back rails. The cover would be easy to replicate except for the Iridite finish but I have the receiver installed in a Hammarlund SP-600 table cabinet that provides the necessary protection so a top cover isn't really required. Oddly, the B&W artwork in the manual shows the receiver without the cover installed (the artwork is shown above in the header for Part 3.)

photo above: Note that most of the coupling and decoupling capacitors are ceramic disks on this 1958-built SP-600 VLF.

I haven't been able to reliably receive Radio Rossii 279kc from Sakhalin Island due to a digital-data beacon that has started up on 279kc. In late November 2013 I was able to hear Radio Rossii somewhat using the 6' loop antenna but the beacon severely limits intelligibility. Radio Rossii was the only LWBC station that could be received in the West and it now appears to have a case of "chronic QRM." (Radio Rossii LW BC and all other Russian LW BC stations were shutdown Jan. 9, 2014. As an update for 2022, there are no LW BC stations transmitting that I can receive here in the western USA, in fact, there are only a few that are actually "on the air" with most LW BC stations being listed as temporarily not operating or on standby or other vague notations that actually indicate the station is "off the air.")

Although NDBs are MCW signals, all "NDB-chasers" use a BFO (tuned to ~ 400hz offset +/- from IF) to help locate the NDB carrier and then tune to zero beat to copy the MCW (this method results in a nice sounding 400~ note depending on the particular NDB station.) Best results for NDBs has the AVC off, BFO on and riding the RF Gain control.

Nearly all operation of the SP-600-VLF will be with the RF gain throttled back to 5 or 6, Audio gain at about 3 to 5, with the AVC turned off and the BFO on (I've started having the AVC on in an effort to help reduce "pops and crashes" - it helps a little bit is all.) I've found that Selectivity at 1.3kc usually gives the best signal to noise ratio. The Crystal Filter should be set for narrowest bandwidth (about 1 or 2 on the dial scale.) With high noise it's sometimes better to reduce the Selectivity to the narrowest bandwidth (0.6kc) while keeping the Crystal Filter at about 2 or so (I've set my Crystal Filter scale to be widest bandwidth at 9 and narrowest at 1.) A 600Z ohm headset connected to the 600 Z ohm audio output (not the phone jack) gives the best results for weak signal detection. The Noise Limiter and AVC circuits are not very effective on static bursts or electrical "pops" so keeping the 'phones in front of the ears is necessary during these types of conditions.

I'm using a six foot remotely tuned loop antenna (up to Nov 2019, then the Pixel Loop.) Nearly all of the NDBs tuned in seem to have two or three signals on each frequency. Stations below about 100kc require an outdoor wire antenna for best reception since almost all loops can't tune any lower than 100kc. Stations like JJY (40kc) or WWVB (60kc) can be received with the AVC on and with the BFO off which lets the Carrier Level meter function. In this set-up you can watch the meter respond to the pulse-encoded signal that either station sends out. USN Submarine Fleet comm stations NAA, NWC, NPM, NML and NLK are very strong MSK Navy VLF stations in the 19kc to 25kc region of the spectrum. MSK stations will require the BFO to be on. No information can be decoded from these stations and their usefulness to LW enthusiasts is that their exact transmitting frequency is known along with their location so they provide excellent test signals for the VLF region of the spectrum. Below the USN stations are the Russian Alpha stations usually on 12kc, 14kc and 16kc. Again, the data received is meaningless (to us) but the frequencies and locations are known.

My first serious listening session was using my 80M Inverted Vee antenna with the feed line shorted. I logged two newly-heard NDB stations. Not that they were any great DX, being PND 356kc in Portland, OR and BF 362kc in Seattle, WA, but they were new ones (#259 and #260, respectively.) Super smooth tuning with oversize controls only adds to the pleasure of using the SP-600VLF.

Dial Slippage - a Chronic Problem with all SP-600 receivers (but there's an easy solution)  - All SP-600 receivers mechanically drive the tuning using the same set up. A brass drive wheel is rotated with the Tuning knob. This wheel in turn drives, by friction, a brass reduction wheel that is spring-loaded against the drive wheel. The reduction wheel is grooved and mates with the Logging dial driving it, by friction, at its perimeter. Driving the Logging dial shaft tunes the receiver tuning condenser through the gearbox. If contaminates are allowed to accumulate on the friction drive surfaces eventually dial slippage will be the result. Although some SP-600 enthusiasts believe that the "S" spring used for loading the reduction wheel causes the slipping, I've seldom had just the spring be responsible for dial slippage. Almost always, dirt and grease will have collected on the friction surfaces of the brass wheels or on the rim of the Logging dial and this is what is causing the slippage. Thorough cleaning is necessary to correct the problem. Fortunately, all parts are accessible without any disassembly. The brass wheels can be accessed with the receiver on its side and the Logging dial rim can be accessed from the top. Clean all friction surfaces with denatured alcohol. I use several Q-tips to clean the brass wheel surfaces. Repeat the cleaning until the Q-tips don't turn black. On the rim of the Logging dial, I use a small piece of paper towel that is dampened with denatured alcohol. Again, clean until the towels don't turn black. Remove and check the "S" spring. It should be straight or slightly bent out. If it's bent inwards then the spring load will be somewhat reduced. You can expand the "S" spring by just bending it outwards with your fingers. Reinstall the "S" spring. As an added help, check the rotation of the logging dial and how much resistance to movement there is in the gearbox. Years of storage with no use or no maintenance may dried up any lubrication. It would certainly help to lubricate all of the shaft bearings with a drop or two of 10W machine oil. As always, don't "over lubricate" and just apply machine oil only where needed. Also, check that the Dial Lock is completely open and not "dragging" on the Logging dial. Check the SP-600 tuning now. It should not slip and should be "velvet smooth."

UPDATE: Jan. 1, 2018 - The slipping dial is back. Although I haven't pulled the receiver out of the cabinet I can see what I think is the problem. The logging dial rim has a small gouge that I think is causing the slippage since this "dent or gouge" changes the dial friction in the drive wheel groove when the gouge comes around. I also noticed that the logging dial has a significant bend so it isn't really engaging into the drive wheel groove with the same "fit" each revolution of the drive wheel. To repair this will be a receiver out of the cabinet and front panel off since I'll have to dismount the logging dial for straightening and repair of the gouge. I'll do this after the Longwave season is over - probably around March.

UPDATE: May 1, 2018 - A Solution That Works and isn't Difficult to Implement - Slipping dial issue required pulling the receiver out of the cabinet and then disassembling to the point where the front panel could be removed. The dial lamp assembly over the logging dial has to be removed. Then the three screw mounting plate is removed and the logging dial can be removed. Close inspection revealed that near "45" on the dial rim there was a deformation that had a "lumpy" feel to it. Also, between "50" and "55" was another rough area. I carefully dressed these areas with a very fine jeweler's file. The dial also had a warp that was easy to take out with minor flexing of the dial. Upon reinstalling the dial on the hub, I found that the slipping was still happening in the same areas. I readjusted the "S" spring for a greater load against the drive wheel. No improvement.

The Solution - I thought about how improve the "grip" of the brass against brass surfaces and came up with the idea of using rosin. I dissolved some powdered rosin in some denatured alcohol to make a thin (viscosity like water) mixture. I used a small paint brush to apply the rosin mixture into the drive wheel groove. Then I rotated the logging dial to transfer some of the rosin mix to the rim of the dial while applying more rosin to the groove with the paint brush. I let the mix dry (alcohol evaporates.) That did it. No more slipping - none at all! I didn't need much rosin-mix, just a little brushed just into the drive wheel groove worked great. If the rosin somehow disappears from the drive wheel groove in the future, it's very easy to reapply the rosin-mix. Hopefully, the "grip" will last for quite awhile. NOTE: The rosin-mix probably should be reapplied each year for best results. For an update on the rosin/alcohol mix read the update for Jan 6, 2021 further down this page.
 

Sept 19, 2022  0550hrs-0610hrs PDT

MW 408kc - Moses Lake, WA
MOG 404kc - Montegue, CA
TW 389kc - Twin Falls, ID
SX 367kc - Cranbrook, BC, CAN
MEF 356kc - Medford, OR
LLD 353kc - Lenai City, HI
XX 344kc - Abbottsford, BC, CAN
RYN 338kc - Tucson, AZ
POA 332kc - Hilo, HI
DC 326kc - Princeton, BC, CAN

Condx okay, a little late in morning for this early in Sept, very little noise but signals not very strong. MOG and RYN were the only strong signals. Both Hawaiian NDBs heard.

10 stations tuned in 20 minutes. Pixel  Loop.
 

Oct 11, 2022   0535hrs-0610hrs PDT

DC 326kc Princeton, BC, CAN
WC 332kc White Rock, BC, CAN*
OIN 341kc Oberlin, KS*
POY 344kc Powell, WY*
XX 344kc Abbottsford, BC, CAN
AL 353kc Trina, WA*
MEF 356kc Medford, OR
YAZ 359kc Tofino, Van Is, BC, CAN*
RPX 362kc Roundup, MT*
SX 367kc Cranbrook, BC, CAN

JJY 40kc Mt. Otakadayo, Japan - PE Time

Condx much worst than expected for mid-October. Weak signals, no atmospheric noise, tried both Pixel Loop and wire antenna with no real difference. Tuned in JJY 40kc while using wire. 6 new, 16 total

Evening before Time Change

Nov 1, 2022  2215-2230hrs

Once again conditions seem to be poor. Signals are very weak except MOG 404kc. Very few NDBs tuned in or even heard. I did copy YXL 346kc Sioux Lookout, ON and SB 362kc in Sudbury, ON,... so DX NDBs can be received. It really seems like most signals aren't there. It might be where I moved the Pixel Loop which is about in the upstairs-center of the house now. I'm going to move the Pixel Loop back where it was before and see if reception improves. Another test soon,...hopefully with better performance and reception.  2 new, 18 total

Nov 3, 2022  2210-2220hrs

Test reception about the same with the Pixel back in its old location. The few NDBs heard seem to be strong, like DC 326kc in Princeton, BC or MOG 404kc. SX 367kc and XX 344kc were the only other NDBs heard. It sounds like a mass decommissioning of NDBs has happened. It doesn't seem to be the Pixel or the SP-600-VLF since DC and MOG were strong.

Evening After Time Change

Nov 18, 2022

The absence of many familiar NDBs is certainly noticeable. I've tried three different receivers and two different antennas with the same results. I'm receiving stations like DDP 391kc in Puerto Rico (different receiver,) so I'm sure conditions are normal. Several of the midwest NDBs are easily received. But, it seems like a very large number of NDBs have been decommissioned during the summer of 2022. I checked classaxe RNA and there appears to be many NDBs that have been decommissioned (or there are plans to.) This appears to be the same for Canadian NDBs. 

Nov 22, condx seem to be improving but still many familiar NDBs are missing. 

Dec 1, 2022    2207hrs to 2229hrs

LGD 296kc LaGrande, OR*
UNT 312kc Penticton, BC, CAN*
DC 326kc Princeton, BC, CAN
MA 326kc Midland, TX*
RYN 338kc Tucson, AZ
OIN 341kc Oberlin, KS
XX 344kc Abbottsford, BC, CAN
POY 344kc Powell, WY
SBX 347kc Shelby, MT*
MEF 356kc Medford, OR
GGF 359kc Grant, NE*
RPX 362kc Roundup, MT
6T 362kc Foremost, AB, CAN*
SX 367kc Cranbrook, BC, CAN
EX 374kc Kelowna, BC, CAN*
GC 380kc Gillette, WY*
CNP 383kc Chappell, NE*
IAETEU 388kc ? Copied call several times
FMZ 392kc Fairmount, NE*
MOG 404kc Montegue, CA
CO 407kc Colo. Sprs., CO*
MW 408kc Moses Lake, WA
LYI 414kc Libby, MT*
GRN 414kc Gordon, NE*

Cndx seem much better now than in November. Pixel Loop NE-SW. 24 stations tuned in about 25 minutes. Best DX either 6T in Alberta or MA in Texas. 4 Nebraska NDBs. The beacon that ID'd "IAETEU" was moderately strong and sent this call several times - always the same - so it probably wasn't mis-keyed or mis-programmed.

13 new shown with * - total is 31 stations

Dec 4, 2022     2205hrs to 2230hrs

TOR  293kc  Torrington, WY
QR    290kc   Regina Int'l AP, SK, CAN
POA  332kc   Hilo, HI
ODX  355kc  Ord, NE
K2     376kc  Olds-Didsbury, AB, CAN
TW    389kc  Twin Falls, ID
 

Cndx okay, some static crashes from storm in Sierra. A few very weak stations heard below 290kc, RST 119. 17 stations heard, 6 new shown above. Except for a few "blow-torch" signals, most NDBs copied are RST 439 or so. Solid copy but fairly weak signals.
Total for SP-600-VLF is now 37

________________________________

Dec 9, 2022     2215hrs to 2232hrs

WG 248kc Winnepeg, MB, CAN
XC  242kc Cranbrook, BC, CAN
BR  233kc Brandon, MB, CAN
HLE  220kc Hailey, ID
 

Cndx good, storm coming in, some "pops"
Tuned in 9 stations in 17 minutes of listening. 4 new NDBs shown above (all below 250kc.) Best DX probably POA in Hawaii but Manitoba is good DX too (QR also copied.)

Total for SP-600-VLF is now 41

Dec 23, 2022    2205hrs to 2235hrs

JDM 408kc Colby, KS
YWB 389kc West Bank, BC, CAN
HAU 386kc Helena, MT
ON 356kc Penticton, BC, CAN
YXL 346kc Sioux Lookout, ON, CAN*
FF 337kc "Hamre" Fergus Falls, MN - new #383
XH 332kc Medicine Hat, AB, CAN
YQF 320kc Red Deer, AB, CAN

24 stations tuned in 30 minutes. Cndx Good.
7 new stations for the SP-600VLF shown above.
1 newly heard NDB, FF 337kc Fergus Falls, MN
being #383 after a very long "dry spell" - last new NDB was in Nov 2020.

Total for SP-600-VLF is now 48

* I had YXL listed on Nov 1 and counted it in the total then but I've listed it again here since Nov 1 wasn't really a log. So 41+7=48 Total

___________________________________

Dec 25, 2022   2145hrs to 2215hrs

YCD 251kc Nanaimo, BC, CAN
VR 266kc Vancouver, BC, CAN
YPW 382kc Powell River, BC, CAN
SB 397kc San Bernardino, CA

17 stations tuned in 30 minutes. Cndx noisy until 2200hrs, then quiet. Pixel Loop N-S,
4 new, shown above.

Total for SP-600-VLF is now 52

19.

RACAL Communications Ltd

RA-17C-12 Receiver with RA-237-B  L.F. Converter

980kc to 30mc Standard RA-17 Coverage

10kc to 980kc with L.F. Converter

Triple Conversion Receiver, Double Conversion LF Converter

SNs: RA-17C-12 sn:N4144       RA-237-B sn:371

1961

(includes NDB reception log)

RA-17C-12 SN: N4144 with RA-237-B SN: 371

Although the Wadley Loop might be the "heart" of the RA-17, it's the elaborate Antenna-RF preselector circuit that allows the receiver's performance to be maximized for any frequency or antenna used. The preselector has a very Hi-Q and has six tuning ranges plus a variable tuning control. This allows exact tuning of the RF amplifier grid input which results in the absolute best transfer of antenna energy to the receiver's front end. The film-strip tuning dial is six feet long and covers 1000kc divided into 1kc divisions. Dial accuracy is to the kilocycle. 100kc calibrator, triple conversion, six selectivity positions from 13kc down to 100hz, +/- 8kc BFO, long-short AVC, RF/AF/S-unit meter functions, 22 tubes (23 tubes in UK version,) four AF outputs with a 3Z ohm 1W audio for external loudspeaker (USA and MK.3 versions,) built-in monitor speaker (with off switch,) 100kc IF output were some of the features on the RA-17 receivers.  

The RA-17 was the first successful receiver to employ the "Wadley Loop" system for oscillator and conversion stability. The first British Royal Navy RA-17 receivers supposedly cost £ 300 each, an equivalent cost then of about $1500. The RA-17 was produced from around 1957 up to around 1973. The RA-17 was upgraded several times but also many variations were produced that were built for special purposes or to be used with other specific equipment. The RA-17 "C series" was built for North American use with standard US-type tubes and US-compatible hardware. 

Racal also produced many different types of accessory equipment for the RA-17, e.g., VLF/LF/MF converters, digital frequency readouts using Nixie tube displays, panoramic adapters, SSB adapters, diversity equipment, RTTY equipment and many other devices. Racal's official name changed several times over the years. Starting out as Racal Ltd, then Racal Engineering Ltd, then Racal Communications, etc., many variations. At one time, Racal employed 30,000 workers building many different types of electronics (not just radio equipment.) It was the third largest electronics firm in Britain and had facilities in 110 different countries. Calder Cunningham died in 1958 and, in 1966, Ray Brown accepted a political position in British government Ministry of Defense, retiring from the company. After 1966, Ernest Harrison was in charge of Racal. The company also owned Decca, Chubb and Vodafone to name a few of their holdings. Several reorganizations and division sales occurred in the 1990s and, in 2000, Thomson-CSF (aka Thalen Group) purchased the bulk of Racal Electronics.

Reception Log for November 10, 2019  -  2150-2215hrs PST  -  Ant 135' "T"

1. YTL 328kc - Big Trout Lake, ON, CAN
2. VT 332kc - Buffalo Narrows, SK, CAN
3. DB 341kc - Burwash Landing, YK, CAN
4. RYN 338kc - Tuscon, AZ
5. YZH 343kc - Slave Lake, AB, CAN
6. POY 344kc - Powell, WY
7. SBX 347kc - Shelby, MT
8. YXL 346kc - Sioux Lookout, ON, CAN
9. NY 350kc - Enderby, BC, CAN
10. IN 353kc - International Falls, MN
11. YWP 355kc - Webequie, ON, CAN
12. ZF 356kc - Yellowknife, NWT, CAN
13. YQZ 359kc - Quesnel, BC, CAN
14. RPX 362kc - Roundup, MT
15. YMW 366kc - Maniwaki, QC, CAN
16. ZP 368kc - Sandspit, Queen Charlotte Islands, BC, CAN
17. EX 374kc - Kelowna, BC, CAN
18. CNP 383kc - Chappell, NE
19. YWB 389kc - West Bank, BC, CAN
20. PNA 392kc - Pinedale, WY
21. YL 395kc - Lynn Lake, MB, CAN
22. ULS 395kc - Ulysses, KS
23. ZSS 397kc - Yellowhead-Saskatoon, SK, CAN
24. FN 400kc - Ft. Collins, CO
25. QQ 400kc - COMOX Vancouver Is., BC, CAN

UPDATE Nov 30, 2019 - I've started using a Pixel Technologies Shielded-Magnetic Loop antenna with the Racal LF combo. So far, the performance of the loop has allowed receiving NDBs east out to Quebec and west to Hawaii. More details as more testing is completed. The Pixel Loop is profiled in the "Loop Antenna Designs" section in Part 4 of Vintage LW Receivers.

UPDATE Dec 6, 2019 - Below is the reception log for Dec 5, 2019 using the RACAL RA17/RA237B with the Pixel Loop. The loop was indoors (second floor) and pointed NE. Conditions were great. 28 NDBs logged in a 25 minute session. One newly heard station, YFM 332kc LaGrande, Quebec, #347. I also logged another newly heard station with the Pixel Loop/RACAL setup a few days earlier, PMV 329kc Plattsmouth, NE, #346

20.

EDDYSTONE

Stratton & Co. Ltd.

 Model 850/2

Receiver #1 - Type S850/2  sn: DEV0003
Receiver #2 - Type S850/2  sn: IN0024
 

MW, LF & VLF Receiver
Single Preselection,
 Single Conversion Superheterodyne
10kc to 600kc
 

1961

Eddystone Model 850/2  SN: DEV0003

Eddystone Radio

Before Radio - Eddystone Radio can trace its beginnings back to 1860 with the partnership-business of Jarrett & Rainsford in Birmingham, England. This company made women's hair pins and costume jewelry. In 1898, a 15 year old George A. Laughton joined the company. By 1904, Laughton was an assistant manager. In 1911, Laughton bought a small merchandise supplier company that was going derelict for £ 50 and renamed that company "STRATTON & CO., LTD." (apparently naming the company after his young son, Stratton Laughton.) During WWI, Stratton & Co. supplied aluminum for the construction of SE5 airplanes and, after WWI, Jarrett, Rainsford & Laughton Co. combined with Stratton & Co., Ltd. with the latter becoming a subsidiary (1919.)

Stratton & Co., Ltd. - Radio 1922 to 1939 - From about 1922 to 1925, Stratton & Co. made various types of radio component parts after becoming involved with the BBC in 1922. It's thought that Stratton Laughton's interest in wireless might have also helped to fuel the company interest in radio. In 1925, Stratton & Co. came out with their first completely built radio set for sale to the public. In February 1925, Stratton & Co. registered the "EDDYSTONE" name and the "Lighthouse" Trade Mark (there actually is an Eddystone Lighthouse located near Cornwall, England. It was constructed in 1882.) 

Post-WWII and After - During WWII, Eddystone produced 4500 transmitters, 7264 receivers and 45,000 other items for the war effort. But, after WWII, the abundant surplus radio equipment availability seriously affected new radio sales, so Eddystone went on to specialize in professional commercial-military types of radio gear that were produced with high-quality construction and good stability as the main factor and selling price a secondary consideration. In 1964, George A. Laughton died and the following year, Eddystone was sold to Marconi Communication Systems. Marconi continued on supplying professional-level equipment with the Eddystone name but eventually sold Eddystone to Megahertz Communications in 1999, who, in turn, sold the company to Ring Communications. The final owner was Sound Broadcasting Systems, who is still the current owner.

An artist's representation of the Eddystone Lighthouse as part of the TM logo.

Model 850/2 Circuit - The 850/2 is a single preselection, single conversion superheterodyne receiver that tunes from 10kc up to 600kc in six tuning ranges. The receiver uses 11 vacuum tubes and two glass tube-envelope quartz crystals. A converter tube is used to combine the LO and Mixer functions. Two IF amplifier stages operating at 720kc are used. Three steps of selectivity are available with a 6kc bandwidth for Voice (not much of that on LW anymore) and two selectable crystal filters provide 1.5kc and 0.4kc bandwidths. Two detectors are provided, one for AM using a standard diode envelope detector and another for CW using a product detector (a 6BE6 mixer tube.) A Carrier Level meter is provided. The Noise Limiter is the typical clipper-type good for pulse noise only. The audio output is about 1 watt and the output impedance is 2.5Z with a 600Z line output (possibly to drive data devices) and a 2000Z 'phones output (C-coupled from the 6AM5 AF output tube plate.) The receiver uses mostly USA-type tubes with British equivalents shown in the manual.

The receiver has separate RF, IF and AF gain controls. The RF/IF gain controls are on a coaxial shaft with the RF gain using the front knob which is a solid red knob or a black knob with red colored index. Antenna input impedance is either 75Ω or 300Ω and an Antenna (Aerial) Trimmer is provided. A muting circuit (desensitizing) has rear chassis terminals for its use. A voltage regulator tube is used (VR-150/0D3) and the power transformer has a dual primary for 110vac or 220vac operation (on standard production models.) 

Mechanically, the 850/2 uses die-cast aluminum front panel that has a large slide-rule tuning dial that is 13" wide with a logging dial system that provides 2300 divisions for accurate frequency reset. The chassis is actually made of of three individual sub-chassis that are bolted together. The central chassis is die-cast aluminum and houses the RF front end and tuning condenser. The IF/AF chassis is made out of brass while the Power Supply chassis is made out of steel. Since all three chassis are painted gray on all sides, it's not readily apparent that different metal materials are used in the construction.

photo above: The top of the 850/2 chassis of IN0024. The left side is the power supply chassis. Note the standard production power transformer and the movable jumper for selecting primary voltage. The smaller can with the tube on top is the BFO. The center chassis is cast aluminum with V1 RF amp and V2 Converter tubes and the tuning condenser located under the shield-cover. The right side chassis has the two crystal filter assemblies in front (the crystals look like vacuum tubes and have tube shields installed.) The three IF transformers are in the center and the audio output transformer is rearmost. The missing 5Z4G rectifier tube has a solid-state replacement installed (next to the 0D3 regulator tube.) I've installed a 5V4G rectifier since this photo was taken.

SN: IN0024

This 850/2 is the first version of the Eddystone LW receiver I was able to obtain. It wasn't complete and had several cosmetic issues, some of which were unsolvable - like the missing cabinet or the oxidized paint on the dial scale. But, it functioned fairly well and piqued my interest in what the capabilities of the design could be.

Model 850/2 SN: IN0024

The Property Asset Tag - Note the small red and silver property tag at the upper right corner of the front panel,...this property asset sticker has "PROPERTY OF AERONUTRONIC" at the bottom of the tag. Aeronutronic Systems, Inc. was a division of Ford Aerospace that was established around 1956. When Ford bought Philco around 1961, they merged Aeronutronic with Philco-Ford and, in 1963, the name was changed to "PHILCO AERONUTRONIC" and that company became NASA's main contractor for communications systems. Although they had a history of working with NASA communications systems, it seems many other projects were in military defense, like the Sidewinder, the Minuteman and the Trident Missile programs. The company became Ford Aerospace & Communications in 1976 and then Ford Aerospace in 1988. The company was purchased by Loral in 1990 and then sold to Lockheed-Martin in 1996. Why an aerospace-communications company would have needed a British MW-LF-VLF receiver is unknown.

photo left: Note the differences between IN0024 and DEV0003. No red RF gain knob is the most obvious. The "Made in England" is not under the EDDYSTONE tag. Other differences are the power transformer, the data plate location and rear panel terminals.

Data plate for IN0024

For now, I'll wait on the front panel removal and dial clean-up until I come up with a better set of tools for extracting tiny little set screws, or, until a duplicate knob turns up somewhere.

More on the front panel removal a little further down in this write-up.

In the meantime, some performance testing,...

I injected test signals using the HP-606 RF Signal Generator that were measured using a DFC and then checked the RF tracking of the receiver. For the most part, the typical error was about 1.5kc to 2.0kc on Bands 1 and 2 which is very good (the two highest frequency bands.) The error on Band 5 is about half a kilocycle but that's actually quite a lot at 24kc. Most RF signal generators don't cover VLF with the lower limit usually being about 50kc or so. Many times, the VLF bands on LW receivers haven't been aligned due to a lack of suitable equipment. But, I have the General Radio Type 1001-A RF Sig Gen that has the lower frequency limit of 5kc, so alignment on Bands 4, 5 & 6 will require using that GR instrument. An inspection showed that Bands 5 and 6 still had the original sealing wax on the adjustments (so, they've never been realigned since the factory alignment 60 years ago.) I'll probably do a complete servicing of the 850/2 that includes tube testing and a complete alignment. But first, I need to do some more test listening to see if any other issues turn up. A couple of logs are shown to the right (using the Pixel Loop antenna.) I started pretty late in the LW Season so signals were weaker and noise levels somewhat higher than a month earlier, even using the Pixel Loop. The "blowtorches" like MOG, XX or RYN are still strong, just the DX signal levels are dropping fast.

Dismounting the Front Panel

This seeming easy task is far more involved than one would think. If you know the procedure and watch out for the hidden Antenna Trimmer shaft coupler the front panel dismounting job shouldn't present any problems. But, I had a broken set screw on the Selectivity knob that required special tools to remove. Another surprise was the dial glass made from 1/4" plate glass. Details follow,...

June 1, 2022 - Well, I've had the 6" long drill bits for quite a long time but I've finally had a chance to try them. I ordered two each of .062" diameter and .125" diameter bits. I started with the .062" to get a pilot-hole then moved up to the .125" bit and it made short work of the set screw. No damage to the knob or the shaft during the removal procedure. Entire time to remove the set screw (with these special tools) was about five minutes. I still had good threads in the brass knob hub but I went ahead and "chased" the 8-32 threads with a tap just to be sure. I then installed a new blade-type set screw to complete the job.

Once the knobs could all be removed, then the control and switch mounting nuts could be removed. Then the nomenclature plate could be dismounted. It was held in place "lightly" with a piece of double-sided tape on its backside. The grab handles had to be removed. The left-side handle had both mounting screws bent - probably from a drop sometime in the past. Then the four counter-sunk panel brass mounting screws were removed. The dial should be set to the far left side (full mesh on the tuning condenser) to loosen the set screws in the tuning condenser coupler. The S-meter wires had to be disconnected. The antenna trimmer shaft had to be loosened at the coupler. I didn't know about the shaft coupler since it's located inside the RF box and hidden by the shield cover. So, of course, I broke the coupler in the removal process. The antenna trim shaft has two "C" clips and a brass shaft panel bushing that shouldn't be removed until the panel is completely dismounted. The front panel shouldn't be dismounted until the chassis is elevated about 2" (I used wooden blocks) to take the chassis weight off of the panel.   >>>

The first thing noted was that the dial glass is .250" thick plate glass! I was going to replace this but I've decided that the chips aren't that bad and certainly don't affect the strength of the glass - besides, it's part of the history of the receiver,... the history of being dropped, that is. The dial scale had minor surface corrosion that did affect the paint somewhat. I had to be careful cleaning so as not to do more damage. The paint was "chalky" and easily flaked off.  After cleaning, a very close examination does show some deterioration but, when mounted and viewed with the .250" thick dial glass in place, the flaking isn't noticeable at the normal distance one is from the receiver when operating.

For reassembly, the two bent screws for the left-side grab handle had to be straightened. This was a rather easy process of inserting each screw into a brass-jaw vise with the bend oriented correctly and then using a ball-peen hammer to straighten the bend.

To repair the coupler was also rather easy since the break was at the flexible metal connections. These pieces were brass and with a little cleaning with a jeweler's file the pieces could be tinned with solder. I made a jig to keep the two coupler pieces inline and then soldered the breaks. The solder repair was quite strong and the coupler worked very well.

The intent of removing the front panel was to replace the chipped dial glass - that didn't happen because the glass was .250" thick plate glass. Also, I intended to clean the dial scale - that didn't happen since what appeared to be dirt was actually surface corrosion problems. I guess the grab handle repair and a few other minor mechanical issues that were corrected might have been necessary. The dial scale and dial glass do look a lot better now - not perfect - but better.

Another EDDYSTONE 850/2   SN: DEV0003

Nov 17, 2022 - DEV0003 arrived yesterday. As known before purchase, the bat-handles on the NL switch and the AM-CW switch are totally missing. The original weird AC power receptacle is missing. Since this receiver is virtually complete with the cabinet, I'm planning on using IN0024 as a "parts source" - not a "parts set" - but, just as a source of the correct original parts to replace those missing on DEV0003 - actually, a "parts swap" would be more correct. Since IN0024 isn't complete anyway, it won't be any worse off if a few parts are swapped to make DEV0003 a nice example of the 850/2. For IN0024, I'm planning on installing standard toggle switches with black rubber "toggle boots" on the switch handles. That should look pretty good and easily solve an issue that appears to be common on Eddystone receivers. Before the swapping begins though, I'm going to test the functionality of the DEV0003 receiver to see if there are any operational issues.     

NOV 18, 2022 - I did an initial test using a 163' end-fed wire antenna to the 300Z input. 60kc WWVB on 56kc. NLK 24.8kc on 22kc. No AM-BC stations heard. Switched to Pixel Loop. Several AM-BC stations heard. MOG 404kc heard (and this was a 1545hrs in the afternoon.) Log below for initial nighttime test results on Nov 18,...followed by post-alignment logs.

DEV0003 Top of the Chassis

note the different (but original) power transformer and the location of the data plate

Nov 18, 2022  1905hrs to 1920hrs

MOG 404kc Montegue, CA
DDP 391kc San Juan, Puerto Rico
CNP 383kc Chappell, NE
YAZ 359kc Vancouver Is., BC, CAN
MEF 356kc Medford, OR
XX 344kc Abbottsford, BC, CAN
OIN 341kc Oberlin, KS
RYN 338kc Tucson, AZ
DC 326kc Princeton, BC, CAN
RPX 362kc Roundup, MT
GC 380kc Gillette, WY
GRN 414kc Gordon, NE

Cndx good. Pixel Loop. 12 NDBs in 15 min.
DDP in Puerto Rico best DX

Nov 22, 2022    1910hrs to 1930hrs

MOG 404kc Montegue, CA
TW 389kc Twin Falls, ID
CNP 383kc Chappell, NE
RPX 362kc Roundup, MT
OIN 341kc Oberlin, KS
RYN 338kc Tucson, AZ
MA 326kc Midland, TX
LGD 296kc LaGrande, OR
QT 332kc Thunder Bay, ON, CAN
SBX 347kc Shelby, MT
SX 367kc Cranbrook, BC, CAN
YWB 389kc West Bank, BC, CAN
LYI 414kc Libby, MT (decom'd but still on the air)

Post-alignment test, Pixel Loop, QT best DX, 20 total

Nov 25, 2022    2145hrs to 2215hrs

MW 408kc Moses Lake, WA
JDM 408kc Colby, KS
SB 397kc San Bernardino, CA
FMZ 392kc Fairmount, NE
EX 374kc Kelowna, BC, CAN
GGF 359kc Grant, NE
MEF 356kc Medford, OR
PND 356kc Portland, OR
POY 344kc Powell, WY

Later session, better cndx. Pixel Loop.
23 NDBs heard, 9 new for DEV0003,
new shown above. Total 29

Best DX - DDP 391kc Puerto Rico (again)

Nov 29, 2022    1910hrs to 1925hrs

Cndx okay. 12 stations heard but none were new for DEV0003. Too early in the evening. Better cndx a little later, like around 2200hrs.

_____________________________________________________

Dec 27, 2022      2155hrs to 2215hrs

AE 351kc Albuquerque, NM
LLD 353kc Lanai City, HI

15 NDBs tuned in, two new, shown above, Pixel Loop E-W
Also heard DDP 391kc with strong signal. Total 31

Details on the Minor Stuff

Minor Problems Noted - Nov 18, 2021

Dial pointer sticks at far left of scale. Applied a few drops of machine oil to loosen up the two sliding tubular rods and the solid rods that the dial pointer assembly rides on. Works better now with no sticking.

Tuning slips and has weird tactile feel when tuning. The clutch was set at the minimum setting. Reset to about 75%. There appeared to be a little grease on the clutch and on the rim of the drive wheel. I cleaned the grease off of both pieces with alcohol. The tuning was still kind of "mushy." The flywheel wasn't tightened on the shaft and was slipping and moving differently than the tuning shaft resulting in a strange feel to the tuning. Luckily, there's an access hole in the front frame to tighten the flywheel set screw (without the access hole it would be a front panel off just to tighten the flywheel set screw.) The loosened set screw was probably a result of shipping.

BFO calibration off by 3kc - zerobeat at -3kc. Checked the air variable and it's set correctly so the BFO will have to be reset at the adjustment on the bottom of the BFO coil can. This powdered-iron slug adjusted without any issues. Probably a result of shipping.

Swapped switches from IN0024. Used the AM-CW switch from IN0024 for DEV0003. I had to use the AGC switch from IN0024 because the NL switch on IN0024 has a broken bat. The AGC and the NL switches are identical parts.

NL cable shielding shorting input. This was discovered when I was swapping the NL switches. Reason was that the center conductors were very short and didn't allow enough clearance for the shields that are tied together from each cable very close to the switch terminals.

Nov 21, 2022

Dial calibration seemed off about 4kc on Band 1 and about 5kc on Band 4. This was caused by the BFO being -3kc off. Also, a slight adjustment of the pointer's mechanical position on the dial string was necessary to have it agree with the logging scale.

Further testing using a RF signal generator input showed that Bands 1 and 2 are "spot-on" accurate. Band 3 is off by 3kc. Band 4 is off by 6kc. I didn't check Bands 4 or 5 because it appears that only Bands 1 and 2 were aligned. The alignment of Bands 4, 5 and 6 requires a special signal generator like the General Radio Type 1001-A (I have two of them) or a very stable Function Generator can also be used (probably a modern synthesized function generator would work fine.) This same alignment problem was found on IN0024 in that the Bands 4, 5 and 6 had NEVER been aligned, in fact, sealing wax was still present on the adjustments. However, Bands 1, 2 and 3 were close and had obviously been aligned. So, DEV0003 will require a tracking alignment on Bands 3, 4, 5 and 6. I do use Bands 4 and 5 quite a lot and the Russian RSDN-20 signals are on Band 6.

RF Tracking Alignment

RF Tracking - Bands 1 and 2 were already accurate so no tracking alignment was performed on those two bands. Bands 3, 4, 5 and 6 are unusual in that an adjustment must be performed for the central part of the range. This is because of the low frequencies involved. Each band was about the same in that the low end of the band adjustment was causing the tracking errors. Once the upper end was set only the low end and the central region required going back a forth a few times to achieve good accuracy. Again, due to the low frequencies involved, the BFO (set to zero) has to be used. I did the entire RF tracking alignment using the GR Type 1001-A RF Signal Generator. I had a digital frequency counter connected to Type 1001-A for input frequency accuracy. No special tools were required, a plastic 1/4" hex female tool, a plastic blade screw driver and a plastic male hex tool. Specified dial accuracy is 0.5% from 600kc down to 100kc and 2.5% below that. After the tracking alignment DEV0003 easily met specifications.

As can be seen in the photo to the right, all RF tracking adjustments are located under the chassis requiring the receiver be placed on its side for alignment. It's not necessary to remove the shield from the coil box. All adjustments are very clearly identified and shown in the manual. The RF tracking procedure is very brief and only provides the necessary information making it very easy to follow.

Note the hole in the front frame of the panel just behind the Tuning knob. This is the access hole for tightening the flywheel weight set screw. Also note that the fiber terminal board below the power transformer with the proper silk-screen nomenclature indicating that the transformer, despite being different, is original and is a single winding primary for 110vac input.

Post-alignment Testing - I didn't put DEV0003 back into its cabinet just yet. I set the receiver up to run with the Pixel Loop. In the early evening, I tuned in 13 NDBs within about 20 minutes of listening. Best DX was QT 332kc located at Thunder Bay, Ontario. Dial accuracy was very good, within 1kc but being an analog dial that's subject to interpretation and the setting of the BFO. That's why Eddystone included the logging dials. I also went down to WWVB 60kc and it tuned at just over 59kc, so pretty accurate, easily within the 2.5% spec. WWVB was down in strength but that's due to using the Pixel Loop with its 150kc low end. You can actually use the Pixel Loop below 150kc but it's just that signals really begin to drop off in strength the further down in frequency you go (WWVB is a very strong signal.) I'll probably install DEV0003 back into its cabinet tomorrow. See log for Nov 22 above.

DEV0003 underneath

DEV0003 Operation

Nov 24, 2022 - DEV0003 is back in its cabinet.

Nov 25, 2022 - Tested Band 5 by tuning in NLK 24.8kc, NAA 24.0kc, NPM 21.8kc and NWC 19.1kc. All of the USN MSK stations seemed to be transmitting except for LaMoure, ND. NLK very strong (as usual) and NWC not very strong (it's halfway around the world in Australia.) One thing noted is that the BFO setting really affects and determines the dial accuracy on VLF. With BFO exactly at zero, stations are exactly where they should be on the dial.

Nov 27, 2022 - Taking my own advice, I made up a cable to run from the 600Z output terminals to a 1/4" phone plug. I then used a 1/4" phone "double female" (1/4" phone jack to 1/4" phone jack) barrel adapter so I could then plug-in any 600Z load using a 1/4" phone plug - like the 600Z phones. There's so much audio available with this method that the "LINK" jumper must be installed to connect the attenuator. This works perfectly with lots of audio with very little distortion. If the PHONES jack on the front panel is used, the audio is taken from the AF Output tube plate through a capacitor to the front panel jack. Running from the 600Z line uses the audio output transformer winding.

Using Selective Level Meters as Longwave Receivers

Rycom R1307A/GR  SN:538 - as acquired, it looked good,...from a distance. Obvious cosmetic problems are the National HRK tuning knob, a couple of incorrect bar knobs, a front panel "creamy white" repaint that oversprayed most of the screw heads and an oxidized spray-on clear-coat over all of the knobs. Several weak tubes, worn dial gears and alignment issues were the electro-mechanical problems found.

If you're interested in acquiring a SLM you'll have to do a little research first. There are some types of SLMs that won't work very well at all as LW receivers. A good example of an unusable SLM is the common Sierra Electronics Corporation Model 125B. This is a vacuum tube model Frequency Sensitive Voltmeter. I have an example that's fully operational with a good set of tubes and I have performed a full alignment on the instrument. However, the Model 125B doesn't have a BFO to help locate weak NDBs and this makes it almost useless as a LW receiver. A BFO is absolutely essential because virtually ALL signals below 500kc are CW, MCW, MSK, Pulse Encoded, etc. Only the few TWEB NDBs and the very few LW BC stations left will have Voice transmissions. Without a BFO, you'll hardly hear any signals below 500kc. Another example of an ineffective SLM was a Cushman that was loaned to me by fellow ham and LW enthusiast, K7SSB. The Cushman was a solid-state model that did have an on-board BFO with USB and LSB capabilities. It didn't matter, I couldn't pick up any signals using it. K7SSB was also disappointed with the Cushman's performance as a LW receiver and he eventually sold it on eBay. But,...on the other hand, the following are a some SLMs that work great as LW receivers,...

One SLM that's a "standout" both in looks and performance is actually labeled that it's a "Radio Receiver." It was built by Rycom for the U.S. Navy. Rycom is the trade name for Railway Communications Inc., a company that built (and still builds) many types of measuring and locating devices.

Rycom R1307A/GR - Radio Receiver
 

Circuit - The U.S. Navy wanted a rack mount version of Rycom's portable SLM, the Model 2147A, so Rycom produced the R1307A/GR for the Navy. The R1307A/GR is a well-known and great performing SLM that really acts more like a radio receiver. It even has "RADIO RECEIVER" engraved on the front panel,...probably because 95% of the circuitry IS a radio receiver. The circuit is superheterodyne with a 2215kc IF. 17 tubes are utilized with four of those being nuvistor-type tubes (2-6CW4 and 2-7586.) Also, two transistors and several solid state diodes are used in the circuit. Frequency coverage is from 3kc up to 800kc in five tuning ranges with AM, USB, LSB, BFO and FM mode selections available. A single RF amplifier (called a Video Amplifier) acts as a cathode follower using a 7586 nuvistor tube. The Mixer is also a 7586 tube. Four IF bandwidths can be selected, 1kc, 2kc, 4kc and 8kc with each bandwidth determined by individual crystal bandpass filters. Three stages of 2215kc IF amplification are utilized. Separate detectors are used with an AM detector, product detector for SSB and CW signals and a discriminator-limiter for FM signals. As expected, no AVC is used since this is measuring device so the input signal level has to be controlled with the attenuator. There's an external audio output that's 600Z impedance, a built-in loudspeaker that can be switched on or off and a 'phones output on the front panel. Audio output is provided by push-pull 6AQ5 tubes. The large arced (and illuminated) dial features a two-speed vernier control of the tuning. The entire chassis is covered with a perf-metal housing.

Matching Antenna Z to Input Z - The R1307A/GR has a very high input impedance of  3000 ohms but that's because the INPUT is capacitively-coupled directly into the LP filter and attenuator before going to the RF cathode follower (called a Video amp) and Mixer stages. The Hi-Z input should be expected for a "volt meter" since you wouldn't want to "load down" whatever signal source you intended to measure accurately. But, for finding and measuring field strength or locating parasitics one would think that there was an external impedance matching device or a set of specifically "tuned" antennas for use as a calibrated field strength measuring device. However, nothing is mentioned in the USN manual (NAVELEX 0967-422-2010) about matching the antenna Z (or even the signal source) to the input Z.

Since the object nowadays is to use the R1307A/GR as an effective radio receiver the input Z should be matched to the antenna Z for best transfer of RF energy. Most antennas are going to have a much lower impedance than 3000Z, even end-fed wires. It's certainly possible to make a small balun with a high ratio, something around 40:1, to allow a better match for low-Z antennas. As a test, I connected an end-fed wire balun "backwards" so the Hi-Z side went to the receiver and the Lo-Z side went to a Pixel Loop. The measured gain increase was about 20db at 500kc but below 150kc the signal response dropped dramatically. This happens even using a wire antenna (which indicates the balan isn't designed for LF or VLF.) A small preselector would be an even better addition but the LF and VLF tuning range necessary would probably require a "homebrew" type of project for such a uniquely-specific, custom device. The "un-un" as a Z-match works fine for MW, especially with the Pixel Loop.

photo above: Top chassis of the R1307A/GR - The four modules in the center of the chassis (with blue labels) are the four crystal filter bandwidth modules. To the right is the Product Detector and FM lim/disc module. The strip in front of the Prod Detector is the 2215kc IF amplifier module. Directly to the left of the IF strip is the shield covering the tuning condenser. To the left of the crystal filter modules are the two 7586 nuvistor tubes that are the RF cathode follower (called a video amplifier?) and the mixer tubes. The power supply is at the right rear and the audio output is at the rear left of the chassis. Note the red fabric cone of the loudspeaker (water proof.) The greenish residue next to the LP Filter appears to have been from a "stick-on" label. Trying to remove the residue would probably damage the Iridite finish of the chassis.  Photo was taken after rebuild.

I was sure the creamy white paint had been sprayed over the original Navy Gray. This caused the engraved nomenclature to "fill" since the original fill paint was never removed. As a result, the new nomenclature fill couldn't be done in the correct manner since the engraving was already "filled." Close examination showed that a lot of the nomenclature was "touched up" and some looked like the fill was done with a brush. To repaint the front panel correctly required complete receiver disassembly to have the panel ready for stripping. I use Kleen-Strip because it doesn't contain methylene-chorlide but it actually works quite well. The white paint stripped off almost immediately. Once the non-original paint was gone I could see why the former owner had performed the repaint. The lower center part of the panel's original paint was worn down to the zinc-chromate primer so there was a large area of the lower panel that was yellowish-green. Another application removed the original gray paint down to bare metal however the engraving fill wasn't removed.

Apparently the fill paint was a durable type that was nearly resistant to the Kleen-Strip. A second application was applied only to the nomenclature and was left on for about an hour and a half. This did soften the fill paint enough that it could be removed using a brass wire brush. Even after the brush treatment, about 5% of fill was still adhering to the engraved metal sides. This last bit was removed with lacquer thinner, a dental pick and a brass brush.

Once all of the paint was removed the physical condition problems needed to be taken care of. The panel was bent somewhat. Not severe but it was noticeable. The panel was fairly soft aluminum so straightening was easy. There were lots of gouges and rack rash that had happened over the years. These had to be sanded or filed depending on their location. Final prep is to very lightly go over the entire panel with a hand sander using fine grit paper. This gave the new paint a good surface to adhere to but didn't remove any significant material.   >>>

photo left: Under the chassis. The shield at the front with the holes is the RF tuning circuit. Directly behind upper is the Mixer and RF Cathode Follower section. Directly below is the four Crystal Filter selection switches and adjustments. The rear shield covers the Attenuator circuitry, note the universal joint coupling from the front panel. The silver shielded box (lower corner) is the AC input filter.

I ended up using Krylon Matte Glacier Gray* which was a little bit lighter gray than original but still fairly close. Since the panel had engraved nomenclature that had to be filled, no more than two coats could be used. The first try ended up with too much paint in the engraving so it had to be stripped off. On the second try I only applied one coat which was sufficient to impart the color but not fill the engraving with too much paint.

The nomenclature fill paint should be black so I used Artist's Acrylic in Mars Black. The technique is the paint some acrylic (thinned slightly with water) over the engraving for one control. Let the paint set for two minutes then wipe in one direction only with paper tower wrapped over a flat rubber eraser and dampened with Glass Plus. The paper towel is pre-cut into small pieces that just fit the eraser shape. I make a "stack" of them before starting the nomenclature filling. The rubber eraser gives the small paper towel piece a very flat surface and reduces the chances of pulling the paint out of the engraving. The paper towel can only be used once, then discarded and a new dampened paper towel piece wrapped around the eraser. This is repeated until the excess paint is removed and the engraving fill looks perfect. Also, excess "wipe off" paint has to be removed using a dampened paper towel to keep the panel area clean.   >>>

* Krylon Matte Glacier Gray is a "Fusion" type of paint that combines primer and paint into one mix. This paint might be great for panels or metal pieces that don't have any engraving to fill. Since "Fusion" paints are primers they do have some type of "filler" in the mix. This has a tendency to have more paint than normal accumulate in the engraving making the nomenclature "fill" process much more difficult. Had it not been for the COVID-19 restrictions, I probably would have used an automotive-type paint that was custom matched to the original - although that would have required at least two trips to Reno.

Alignment - The manual indicates that the IF should be sweep aligned but the method described in the manual is quite different in that the input signal is at 120kc where the IF is 2215kc. This means that the IF alignment has the input signal go through the mixer conversion instead of using the IF input directly at 2215kc. The object of the sweep alignment is to maintain a broad, flat bandwidth by being able to observe on an oscilloscope the IF bandwidth curve. I've done sweep IF alignments before but never going through the mixer conversion. Usually the sweep is at the IF input with the 'scope monitoring the IF output at the detector with the sweep ramp output going to the horizontal channel of the 'scope. As expected, the Navy procedure must have used some special visual display equipment since it's not referred to as an "oscilloscope" in the procedure. With standard sweep gear, I couldn't get the IF curve to be stable enough to be sure of any alignment adjustments. Since the IF bandwidth seemed okay I proceeded onto the tracking alignment which was obviously needed.

photo above: The R-1307A/GR after its repaint, several new tubes, dial rebuild and tracking alignment
 

The BFO had been misaligned so that zero beat was with the air variable fully unmeshed. Zero beat should be with the air variable at half mesh so that the BFO can select upper or lower sideband. The "+" the "0" and "-" indicate the direction of the apparent frequency displacement and aren't an indication of upper or lower sideband - not that there are any SSB signals being transmitted in the tuning range of the R1307A/GR anyway. However, its original use might have involved finding and tuning parasitics or subharmonics of USN SSB transmitters. Also the reason for USB and LSB modes. 

If you've used Navy manuals before and are accustomed to their cumbersome procedures then the Rycom R1307A/GR should come through the alignment with better overall performance. The Navy manual also has a few minor errors, like misidentifying the FC J6 as J5 (FM out) several times. The schematic and the alignment instructions are correct. As mentioned before, the sweep alignment requires a special "visual display unit" that apparently isn't a standard oscilloscope. It should be possible to input a sweep signal at the IF input and monitor the detector output on a standard XvsY 'scope for a typical sweep alignment but, unless there's evidence of some prior component replacements, the original IF alignment is probably fine.

The Rycom 3135 can be used as a LW receiver but there are a couple of disadvantages. First is that the bandwidth is essentially "fixed" at 2.5kc. This is a little wide for MCW NDBs and too narrow for AM BC. The IF bandwidth skirts are very steep and AM signals enter and exit the passband abruptly. The BFO is "fixed" since only USB or LSB can be selected and there's no front panel adjustment of the BFO. The dial isn't illuminated although the standard Rycom "push in for fast tuning" type of two-speed vernier is provided. Documentation is not very difficult to find.

One of the advantages of the Rycom 3135 is that it's usually not expensive. Most were used as portables and as a result they are usually banged up to a certain extent. In fact, the example shown is missing its front cover. A rough exterior doesn't seem to affect performance but some 3135s are cosmetically compromised so the prices are usually reasonable. The 3135 is very small and, being portable, doesn't weigh much,...maybe 10 pounds without the batteries installed.

As a LW receiver, the Rycom 3135 will perform adequately but there are many other SLMs that are much more versatile in modes received with better selectivity options resulting in a more pleasurable operating experience. I bought this Rycom 3135 for parts (the knobs) although it does function.       

Hewlett-Packard 310-A Wave Analyzer
 

Hewlett-Packard 310-A - Wave Analyzer  -  Wave Analyzers are SLMs and some types function quite well as LW receivers. However, many of the HP Wave Analyzers don't have a useful tuning range with the majority of models only tuning up to 50kc or so. But, HP did offer a few Wave Analyzers that featured a very useful tuning range. I happen to have the HP 310-A version which is shown in the photo to the left. The HP 310-A's solid-state receiver tunes from 1kc up to 1500kc and also has selectable USB or LSB and AM detection along with 200Hz, 1000Hz and 3000Hz selectable bandwidths. Lowest scale sensitivity is 10uv FS meter reading (maximum signal level) although using this sensitivity depends on how much atmospheric noise is present. With a tuned loop antenna, 10uv FS meter can almost always be used. During high noise periods with a wire antenna, 30uv FS provides better noise immunity. In the "Relative" measurement position the sensitivity is adjustable for best response versus noise. The HP 310-A is a late sixties to early seventies vintage (all solid-state) instrument. The mechanical digital readout is for receiver frequency while the long horizontal scale illuminates a red numeral depending on the sensitivity (max. signal) selected. The red and blue tags above the meter switch are USAF property identification tags. I purchased this Wave Analyzer at an industrial electronic equipment auction for $5.

I find that the performance of the HP 310-A is quite good. It's capable of receiving any LW signals being transmitted with conditions being the limitation. The 310-A has a much lower input Z of 50 ohms versus that of the Rycom R1307A's 3K ohms input impedance. This allows direct connection of antennas to the 310-A input without an impedance matching device. The 310-A doesn't have a noise limiter - mainly, because noise was one of the things the instrument was designed to measure. However, manipulation of the sensitivity versus the atmospheric noise seems to do pretty well for coping with the lack of a limiter. Since this is a measurement instrument, no AVC is provided, so strong signals will over-drive the 310-A, even when using a loop antenna. I watch the meter and keep the measured signal level at about 75% to 95% of FS with the Relative Gain control. Dial frequency readout is "to the kilocycle" accurate. I have received hundreds of DX NDBs from all over North America on my HP 310-A, from DDP 391kc in Puerto Rico to LLD 353kc in Hawaii.

The HP 301-A is such a good LW performer, I picked up another one in March 2021. I had to pay more for this one,...$20. Needs clean up/testing. It does function but not to the level of my first 310A. Needs the switches and pots cleaned to begin with. Sensitivity vernier pot missing (maroon knob.) More details to come,...maybe,...

My conclusion is that Selective Level Meters and Wave Analyzers are designed for measuring RF field strength, finding and measuring RF leakage in transmission line systems, locating parasitics or harmonics from RF sources and other similar applications. Some of the SLMs are absolutely useless as LW receivers. Be sure to read up on any instrument you intend to purchase for LW reception and make sure that others have had success using it for that purpose. The first two instruments I tried, the Sierra 125B and the Cushman, were of the "useless" variety. The Rycom 3135 was barely usable but the Rycom R1307A/GR and HP 310-A are the best SLMs that I've tried and they perform very well as LW receivers.

photo right: The Sierra Model 125B Frequency Selective Voltmeter. The drum dial scale is at a "slant" because it is continuous tuning that has the scale spiral up as the drum is turned about four turns to go from 1kc up to 620kc. Lack of a BFO on the Sierra 125B makes it "useless" as a LW receiver.

Other Vintage Receivers with Some Medium Wave and Low Frequency Coverage

Most of the receivers profiled in Parts 1, 2 and 3 were specifically designed for MW, LF and VLF coverage - generally 600kc down to 15kc. Many other receivers were offered in versions that covered a portion of either the MF or the LF spectrum. I've profiled seven receivers of those types with MW and LF coverage (but not VLF coverage) in parts 1, 2 and 3. Here are four more "good ones" that cover MW and LF.  

Using coil sets F - 930kc to 480kc, G - 430kc to 200kc, H - 200kc to 100kc, J - 100kc to 50kc - The HRO-60 is a very good performer with long wire antenna or loop. These coil sets were generally optional equipment with both pre-WWII HROs and post-war HROs. The WWII military HRO versions originally included a complete set of 9 coils, including those for MF/LF coverage. Of these military WWII versions, the HRO-W and the RAS are the most common. LF coil sets can be used in any of the HRO receivers but alignment to the specific receiver is required for best performance. Double preselection (two TRF amplifier stages) are used in all coil sets for the HRO receivers (although the HRO-60 is also double-conversion using coil sets B, A, AC and AD.) IF is 456kc on almost all versions (HRO-60 is 455kc IF.) Notice that there is a gap in frequency coverage from 480kc to 430kc. This was because of the HRO's IF of 456kc (or 455kc.) The WWII RAS used 175kc IF and that allowed it to cover from 195kc up to 500kc without a gap in the frequency coverage (the USN wanted complete coverage in the 400kc to 500kc range which the standard HRO couldn't provide.) The RAS receiver must be used with RAS coil sets identified as coil sets 1 through 7 on a metal tag on the coil panel. Later HROs, like the HRO-50 and HRO-60, provide excellent performance using the F, G, H and J coil sets. The LW coil sets for these later receivers are more difficult to find and are usually somewhat expensive because of that. Photo shows the mid-fifties HRO-60R with SC-2 coil storage and speaker panel both mounted in the MRR-2 table rack. I have 11 coils sets for this receiver covering 50kc to 430kc, 480kc to 30mc plus bandspread 15M and bandspread 6M.

NOTE: The F coil 920kc to 480kc usually has enough extended lower tuning range to actually cover 630M (472kc to 479kc) although the plastic dial strip is not calibrated lower than 480kc. When aligning the F coil, 480kc is at 10 on the PW-D and that allows the actual range to extend somewhat lower in frequency with "0" on the PW-D usually being about 470kc. The PW-D can be used for accurate frequency reset when tuning in the 630M band.

Covers 100kc to 200kc and 200kc to 400kc on the LF and MW bands, 2.5mc to 20mc on HF bands - Excellent with loop antenna, a bit noisy with long wire antenna (depends on your location.) If you can match the antenna Z to about 110Z of the receiver antenna input, noise response will be greatly reduced. Good dial accuracy. The BC-779 is probably the most popular of the military WWII versions of the SP-200 series. Some BC-779 receivers were built by Howard Radio Co. under contract. Band spread was not provided on the LF or MW frequencies. SP-200LX is the designation used for any pre-WWII or non-military version of the "200 Series" LW receiver. Photo shows the SP-200LX version. IF is 465kc on all versions and double preselection is used on all bands.

The earlier version of this receiver, the SP-100LX (1937-39) with the same frequency coverage, is profiled in Part 1 of this Vintage LW Receiver article.

The MAIN disadvantage of ALL WWII and pre-WWII Super-Pro receivers is the lack of 400kc to 530kc coverage preventing them from receiving 630M amateur signals and any NDBs operating above 400kc.

Hammarlund didn't provide complete LW coverage on any Super-Pro until the SP-600VLF receiver from the mid-1950s.

The CSR-5 was built during WWII. The receiver's frequency coverage was in two sections, 75kc to 530kc (two bands) and 1.5mc to 30mc (four bands.) Each scale on the large illuminated dial was color coded. The CSR-5 has eleven tubes in the receiver with two RF amplifiers, Mixer (also provides Xtal Osc function,) LO (9002 miniature tube,) two 575kc IF amplifiers (dual wave traps are in-circuit to prevent IF interference,) Crystal Filter (Selectivity positions 3 and 4) AVC/NL, Det/1AF, AF output and Voltage Regulator. The RF Gain control is a stepped attenuator type with an average of about 10db of change for each step. AF output is 2 watts into a 10K Z load for loudspeaker, 500 ohms Z line audio and both Hi-Z (5000Z+) and Lo-Z 'phones (up to 1000Z.) The "Crystal" socket and "Crystal-IN" allowed drift-free operation though a crystal-controlled local oscillator function but the receiver still had to be tuned to the intended receive frequency for the RF and Mixer stages to be "in tune."

The CSR-5 actually performs quite well on the two lower frequency bands using a Pixel Shielded Magnetic Loop for the antenna. Many NDBs and several 630M amateur stations have been heard using the Pixel Loop and the CSR-5. The receiver does have a separate power supply that was designated VP-3 that is connected by cable to a connector on the rear of the receiver. In my installation, the VP-3 sets on the floor and the receiver on the desk. The CSR-5 is also an excellent SW receiver and I've used it many times as a station receiver in a vintage military radio set up.

Radiomarine Corporation of America (RCA)  -  Model AR-8506-B

The RMCA AR-8506-B was the MW-SW companion receiver for the LW AR-8510 receiver that is profiled in Part 2 (WWII LW Receivers.) It was primarily for shipboard use during WWII but was used in other various places, such as Coastal Stations, post-WWII. The AR-8506-B tunes from 85kc up to 550kc in two tuning ranges and from 1.9mc up to 25mc in three other tuning ranges. It's a ten tube superheterodyne that uses a 1700kc IF to allow uninterrupted tuning in the two lower frequency bands. A NE32 (G-10) bulb is used as a voltage regulator. Being designed for shipboard use, the AR-8506-B will operate on 115vac or 115vdc. Generally, the receiver was rack mounted in a RCMA 4U Marine Console during WWII but later receivers were in table top cabinets (as shown in the photo right.) The control between the AF GAIN and the MAIN TUNING is a BANDSPREAD control that actually is a vernier frequency control. The built-in speaker can be disabled for exclusive 'phones use.

The AR-8506-B is actually a pretty good MW receiver that was used post-WWII in Coastal Stations such a KPH and in some laboratories. The 1700kc IF might result in some AM-BC leakage into the IF from nearby stations using that frequency. Fortunately, there aren't too many stations on 1700kc. There is an internal wave trap that should be adjusted for 1700kc which should eliminate any leakage. The receiver does use some unique parts that are difficult to find if they are missing or damaged. The PS filter capacitor is a "plug-in" multi-section that probably would have to be rebuilt if defective. The NE32 is sometimes difficult to find. When operational and used with a good antenna, the AR-8506-B will perform quite well. The Signal Corps also had their version that was identified as R-203/SB. The AR-8506-B shown is from 1953,...by 1958, RMCA's sophisticated AR-8516 replacement shipboard receiver was introduced.

Regenerative TRF Receivers versus Superheterodynes on Longwave

Regenerative receivers have some advantages over the typical superhet receiver on LW. For example, receiver internal noise - regen sets are quiet and don't add much noise to an already noisy part of the spectrum. The frequency conversion required in the superheterodyne can create substantial internal noise in the receiver that limits its weak signal ability on longwave. Also, since a minimal number of tubes are used in regen sets, thermal noise is at a low when compared to a large tube-count superhet. The regen set's ability to be set-up as an Autodyne Detector, that is to produce an oscillating condition without a BFO, is also an advantage. With a superhet it is necessary to use the BFO to set-up a condition where the carrier can be heard however the BFO in a superheterodyne can sometimes mask weak signals. Though most BFOs are very lightly coupled in early superhet receivers to prevent "masking" this is not always the case in modern receivers. Additionally, when the regenerative set is oscillating, it is doing so at the tuned frequency while a superhet, using a BFO, is actually providing an audible heterodyne by injecting an oscillator signal at the detector that is somewhere near the intermediate frequency. It is the level of the injection that is important to weak signal copy. BFO frequency drift can also be a problem not found on regen sets. >>>

photo above:   1923 RCA-Wireless Specialty Apparatus Co.  IP-501-A during a LW performance test. The receiver is powered by a Lambda 6vdc 4A power supply and a RCA Duo-Rectron regulated B+ power supply. The -C bias is supplied by three AA batteries in series. The antenna used is a 80M ham inverted vee with the feed line shorted. Since the regenerative detector is set to oscillate for NDB copy, some RF energy will couple back to the antenna. By wrapping a pick-up wire around the antenna lead-in, a digital frequency counter can used to provide an accurate frequency readout. This set-up only works while the detector is oscillating (autodyne.) The IP-501-A is tuned to local NDB "NO" from the Reno-Tahoe Intn'l AP (NOTE: NO 351kc was decommissioned in 2013.)   photo taken in Virginia City at WHRM

One of the best LW receivers was the RBA series built for the Navy during WWII. These receivers use three cascade TRF amplifiers feeding a non-regenerative triode detector followed by three audio amplifiers - in essence, the typical TRF receiver of the late twenties. However, that's where the similarity ends. The RBA also uses a "tracking" BFO that tunes via an additional ganged section of the five-gang tuning condenser. This allowed the BFO to always be 1kc above the tuned frequency and provide the heterodyne necessary to demodulate CW. Also, the RBA featured a "tracking" auxiliary gain control that was gear-driven from the tuning mechanism and kept the gain level constant throughout the tuning range. However, the most useful feature found on the RBA is its fabulous Output Limiter circuit. It is capable of suppressing most of the intense amplitude pulses of noise bursts, like lightning strikes, but still allow copying a CW signal and preserving the hearing of the radio operator. The RBA was used by the Navy for about two decades after WWII ended and its superior performance illustrates what can be accomplished in TRF design when cost was not an issue - the RBAs sold to the Navy for $3000 a piece in the 1940s.

Now, all of the above isn't saying that a vintage superheterodyne can't do a good job on LW reception - I'm just saying the regen and TRF receivers can also do a great job on LF. The superhet, when specifically designed for LW, with low noise tubes and circuits, can perform quite well on LW when used with the proper antenna. However, many superhets just added a portion of a LW band to a receiver that was really designed for HF. These types of superhets are common and their LW performance is usually barely adequate. There are exceptions with the National HROs (using F, G, H and J coil sets,) the Hammarlund SP-200LX (aka BC-779) and the RCA AR-88LF (aka Camden CR-91, also the Montreal-built updated CR-91A) being noteworthy as high performance superhets that do a great job on their limited coverage LW bands.

Many casual LW listeners aren't aware that all of the "top performing" LW receivers must be operated with some type of low-noise antenna, even in a RFI-quiet location, to achieve DX reception on LW. In reality, most "high-end" LW receivers have about the same abilities and superior performance is more dependent on the receiving location, the operator's experience and the antenna type used rather than on the type of receiver being used. If the LW superhet user runs his receiver with a tuned loop antenna, a shielded magnetic loop antenna or a low-noise wire antenna like a Beverage, he will find the signal to noise ratio is greatly improved and, in a quiet location, he should be able to receive ample LW DX.

1. Hammarlund SP-600VLF-31 - Not unexpected. It's an easy to use, easy to maintain, very sensitive LW receiver, although this high sensitivity also produces a fairly high noise floor almost mandating the use of a well-designed loop antenna. But, the SP-600VLF is one of the few receivers that has more than enough sensitivity and gain to produce excellent reception using a shielded magnetic loop. Good condition, functioning SP-600VLF-31 receivers are expensive but the Dero versions seem to sell for much less (and they are SP-600VLF receivers.)   Update 2022 - I should add some information on the selling price of the SP-600VLF-31 receivers. In April 2022, a very nice condition Hammarlund SP-600VLF-31 was put up for auction on eBay. I was astounded by the winning bid of $2605.00! The receiver was in excellent condition and had been checked out and recently aligned, so it was the best example I've seen come up in quite a while. Certainly the operational condition of this particular receiver along with its excellent cosmetic condition warranted the high selling price. I haven't seen a Dero version for sale in quite a while but I would think those versions would probably sell for much less and, of course, a lesser-condition Hammarlund '600VLF would also sell for less. The SP-600VLF-31 is a great receiver with tremendous performance potential so I would expect the prices for excellent examples to remain high.

2. RACAL RA-17C-12/RA-237-B - It might be a surprise to many but it's a great performer - the British-built receiver RACAL RA-17C-12 with the RA-237-B Low Frequency Converter. Easily comparable to the SP-600VLF in its ability to pull weak signals out of the noise using a shielded magnetic loop antenna with the additional benefit of "to the kilocycle" dial accuracy. However, the receiver can be difficult to maintain, it is difficult to align and, if repairs are needed, it's physically difficult to access many of the components that are located inside modules that are equally difficult to remove from the cast-aluminum chassis. This maintenance issue is probably the primary reason I don't place the RA-17C-12 and RA-237-B as the #1 on this list. Like all of the "high-end" receivers, the RACAL RA-17 versions aren't cheap and then you must have the Low Frequency Converter which can be very difficult to find (and expensive.) A side benefit of the RACAL combo is its complete frequency coverage from 10kc up to 30mc. Both the SP-600VLF and the RACAL combo are by far the best performing vintage tube-type LW receivers I've used.   NOTE 2022 - Even though the RACAL equipment isn't cheap, the selling prices are substantially less than the Hammarlund SP-600VLF. Figure that a good RA-17C-12 receiver would probably sell for between $600 to $800 and that the LF Converter would probably run between $200 to $400. Total would be quite a bit less than the SP-600VLF and yet the performance is very comparable. The lower price is probably due to the difficulty in rebuilding and maintaining the RA-17 receivers. Also, the unfamiliarity that most USA radio enthusiasts have with RACAL equipment. Some parts are only available from the UK but the "C" version RA-17s were built for the North American users and are constructed with mostly USA-type parts and tubes.

3. US Navy RBA - The RBA is difficult to work on and it's almost a "given" that any RBA in "as found" condition will NEED to be worked on. The major problem is caused by the Hammarlund ACP "hex collar" trimmer capacitors used in ALL of the RF Coils and the BFO coils. These hex collars crack with age and then fail to hold the trimmer rotor in the proper position which then shorts out the trimmer capacitor until it's mechanically repaired. Disassembly and repair (or replacement) of EVERY bad ACP trimmer is required. The ACP hex trimmers can't be accessed directly and each affected RF transformer has to be dismounted from the chassis for repair. It's a difficult process. The RBA is large and heavy so it's physically difficult to work on. It's also hard to find room for the large RBA cabinet with its equally large and heavy, separate power supply and armored cable. BUT, once the RBA is fully repaired, aligned and set-up, it's a great receiver that's well-known for phenomenal sensitivity and dial accuracy. The Output Limiter circuit is one of the best. NOTE 2022 - Most of the time, RBA receivers are found with missing components, e.g., the power supply or, especially, the armored power cable. The power supply AC connector is difficult to find and it's usually also missing. Almost without exception, a RBA receiver will require some work to have it functioning at its best. The ACP trimmers are always a problem. All original components in the receivers are now 80+ years of age. Alignment is very easy if the ACP trimmers' hex collars haven't cracked. Other problems crop-up from the Micamold brand capacitors used. WWII-vintage Micamolds are notorious for high leakage current and for sometimes failing "short circuit." Once you have all of the components necessary for operation and the receiver is in good operating condition, freshly aligned and connected to a large wire antenna, the RBA is almost an unbeatable LF receiver. Getting there can be a lot of work - BUT, at least the parts aren't always in the "unobtainium" category,...like the next receiver (#4.)

4. Collins R-389 - My last pick of the "top" LW receivers would be the Collins R-389, that is,...when it's in good physical condition and it's working correctly. It's a fantastic LW receiver and I would rate it as "one of the best LF performers" except, due to its complexity, frequent maintenance is required. Most of the maintenance will be tube replacement after everything has been refurbished. The circuitry is a paragon of electro-mechanical complexity that will require that the owner has a good electronics background and sufficient experience in both electronic and mechanical rework of top-tier vacuum tube designs. The absolute worst problem is that many of the front-end component parts are unique to the R-389. For example, the 70H-1 VFO and the RF module are unique pieces. Other unique components would be the entire motor-drive tuning, the motorized band switching, the veeder-root dial and the bezel,...to mention just a few. Luckily, the IF, AF and PS modules are identical to the R-390 modules but even R-390 parts aren't particularly easy to find. R-389 front-end parts that might be required for a professional-quality repair are in the "unobtainium" category (after all, only 856 R-389 receivers were built.) Add to that, Collins collectors have driven the price of the R-389 into the STRATOSPHERE and beyond - expensive beyond belief. Even "parts sets" are never found because there are "no such things" as R-389 "parts sets." If you do happen to find a beat-up and missing parts R-389 it will still be priced as if it was a fully functional receiver due to the seller knowing that some Collins collectors will pay "top dollar" for almost anything. If you're willing to become a budget-challenged, electro-techno-mechanical-masochist, then the R-389 might be for you. Again,...and most importantly,...when all is working correctly, the R-389 is a great receiver. The challenge is to get your R-389 operating correctly with its existing unique original parts and to keep it functioning that way if you use it a lot. That's probably why most R-389s are Collins Collector's "shelf-queens."  NOTE 2022 - My opinion about the R-389 hasn't changed much. Even with prices that are in the stratosphere most sellers claim ignorance to any details regarding the receiver they are selling - in fact, early this year, I saw a R-389 on eBay where the seller didn't even bother to remove the top and bottom covers to verify that any of the modules were even present (and he still wanted $2200! Plus shipping! And,...he got it!)   Oct 2022 - Another R-389 showed up on eBay with no interior photos, just two exterior photos, eBay BIN price was $1850 and the receiver was sold within 48 hours. The seller never tested the receiver and knew nothing about it. Dec 2022 - Two more R-389 receivers were on eBay. One was a relist of a deal that fell-through and the other had a semi-rough exterior condition. Prices were $1850 and $1500 respectively. Both sold within 24 hrs. Again, no photos of the interior on either receiver.

Another R-389 NOTE:  I have to reiterate that the R-389 is a first-class LW receiver that has a very low noise response and that allows using large wire antennas that can produce very strong signals. Mine is working at the moment,...but who knows for how long?

These four receivers are about the best of the vintage LW receivers because all four can detect very weak signals that are "in the noise." All four have direct frequency readout with illuminated dials, the SP-600VLF has tremendous sensitivity allowing excellent performance with a shielded magnetic loop, the RBA receivers have the best Output Limiters that are very effective "static crash" noise limiters, the RACAL has a very low noise floor with high sensitivity and "to the kc dial accuracy." The R-389 has a very low noise floor, "to the kc" accurate digital frequency readout and performs very well with large wire antennas. All four have excellent mechanical construction. However, even these top vintage LW receivers can't perform well within certain environments or when LW receiving conditions are poor.

Regardless of the LW receiver used, for effective LW DX reception you absolutely need the following:  FIRST and MOST IMPORTANT is a good receiving location that has very low RFI-noise levels (Radio Frequency Interference, e.g., manmade RF noise.) High RFI-noise areas will limit what even the best receiver can pick-up and separate from the interference. In most densely populated urban areas, LW reception is virtually impossible due to the tremendous amount of interference from almost every electronic device in close proximity operating simultaneously not to mention all of the industrial electrical noise present 24-7. In these types of environments, a shielded-magnetic loop might help but don't expect to hear weak DX signals. At most, "blow-torch" Canadian NDBs or local NDBs are about all that can be expected when listening from a large densely populated urban location.

Second, is a good low-noise antenna. An antenna that "picks up" a lot of RFI-noise will only compound reception problems in a moderately noisy location, making even the best LW receiver a poor performer. Even in RFI-quiet areas, using a low-noise antenna will benefit your reception. In rural areas using a large wire antenna becomes a possibility and what can be heard with this type of antenna is impressive. But, atmospheric noise will limit how often a large wire can be used.

When you have a superb receiver operating in a quite receiving location with a good low-noise antenna then you absolutely must to use headphones for the audio output. You should operate the 'phones directly from the 600Z ohm audio output of the receiver if possible. You'll never hear the extremely weak signals using a loudspeaker. 'Phones are a must. Always have the 'phone cups just in front of your ears to protect your hearing from static bursts. Avoid using rubber cups or padded cushions that surround the ears since this will have the phones in position to direct static bursts directly into the ear canal resulting in "ringing ears" or worst. Try to use "bare cups" or phones with small rubber cups with the cups in front of the ears (on your cheek bone.) WWII LW receivers with Output Limiters, an audio-AVC circuit for actually limiting amplitude impulse bursts, work wonders for saving you from "ringing ears syndrome." The best Output Limiters are found in the RBA receiver and the National RBL receiver. Regular "clipper-type noise limiters" will help but not to the extent that a true Output Limiter circuit does. Also, if the receiver is a superhet and has adjustable selectivity, keep the bandwidth as narrow as possible to reduce noise. Usually 0.5kc to 1.5kc bandwidth is about the best compromise between noise levels and weak signal detection.

Finally, you must have good receiving conditions and that means you must do your LW listening during "the LW season." This would be late-Fall and Winter nights and early mornings (the "LW season" is usually between the Autumnal Equinox and the Vernal Equinox.) The following sub-articles in Part 4 detail some of these MW/LF reception problems and some of the solutions to noise and what types of antennas are best for successful LW reception.

CONTINUE TO PART 4 - What to Listen To On Longwave

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