You are the proud owner of a Collins designed R390A/URR general coverage, HF radio receiver. In many circles, the R390A is considered to be the finest HF radio receiver ever built. Weighing in at 85 lbs, this electro-mechanical wonder was designed in the early 50's and released February 24, 1954 which also happens to be my birthday. Thanks to features such as a 6DC6 first RF amplifier, a suite of Military Grade Collins mechanical filters and full tracking RF and IF sections, the R390A is capable of copying signals down to its -143db noise floor, close to the galactic limit. All this while operating in high over load/strong signal environments.
Originally built by Collins Radio Company in Cedar Rapids, IA, the R390A was designed by 2 teams. The mechanical team being lead by Fred Johnson while the electronics team was overseen by Ernie Pappenfus, K6EZ. Besides Collins Radio, there were 13 other sub-contractors which built R390A's until the last one rolled off the assembly line in 1984. Banks of these fine radios served the country in all branches of the military and also the CIA and NSA for monitoring communications from behind the Iron Curtain during the Cold War years where the R390A was classified TOP SECRET until the mid-1960's. Stories are told that R390A's are still in use by the NSA where senior operators far prefer their quiet, yet stellar performance over modern, mega-dollar receivers from Harris, Racal and Watkins-Johnson.
I hope you enjoy this wonderful radio, unduplicated
in performance and rich in history over the many years of service it still
has to offer.
Chuck Rippel, WA4HHG
Collins Collectors Association
Before powering up the receiver: There is nothing really very different about owning and operating an R390A but there are a few issues to be aware of. By now, you know that this radio is quite heavy! Weighing in at 85 pounds without the accessory cabinet, your R390A is a "boatanchor" in the truest sense. Keep this in mind when considering a location and operating position; placing it on a light desk or TV table might result in this 85 pound radio ending up in your lap! Another consideration is the amount of heat given off by the R390A's 26 vacuum tubes using both 6.3 and 12.6 volt filaments. Make sure the radio has adequate ventilation. Finally, and perhaps most important, before plugging in or powering up the radio, be safe! Make sure your R390A has a good electrical and RF ground.
The audio output of this receiver is much like most other military receivers having a 600 ohm impedance. This means, if connected to a regular 8 ohm loudspeaker, it will sound weak and distorted. The "local audio," that is, the audio controlled by the "local gain" control on the front panel appears on pins 6 & 7 on the left hand terminal block as viewed from the rear of the receiver. The impedance mismatch when using a 4 or 8 ohm loudspeaker can be overcome easily. The first solution is to purchase a 600 to 8 ohm AUDIO transformer. These can be found (at times) at Fair Radio for about $8. An easier solution is found right at the local Radio Shack. Purchase a 70.7 volt line transformer (cat. Number 32-1031) and connect the primary terminals marked "C" and "10" to terminals 6 and 7 on the left hand terminal block located on rear of the R390A. Then, connect the secondary side of the transformer, terminals "8" and "C" to your 8 or 4 ohm speaker. This will result in an 500 to 8 ohm match which will give good performance. A closer match may be realized by using a 25 volt line transformer and using the same configuration as above save for choosing the "1" and "C" taps on the primary side of the transformer. The secondary wires as above in the 70.7 volt line transformer.
The antenna connection is even more simple. The radio has been aligned using the "Balanced" antenna input located on the rear of the receiver. Turn the receiver around and face it. TB-102 will be on your left and TB-103 on the right. The "Balanced" antenna input is located in the upper middle. Examine the connector and notice it has two holes for pins located within the connector. Simply tin your antenna wire and insert it into the right hand pin hole. Insert a wire in the left hand hole and ground it using one of the screws which hold the antenna relay unit to the rear panel. The "Unbalanced" antenna input can also be used but with a decrease of performance unless it was aligned to that input.
If you wish to use the proper connector, there are several approaches from which to choose. A combination of a UG-971/U and a UG-636A will adapt a BNC connector to the "balanced" antenna input. A UG-970/U will adapt a PL-259 to the "balanced" antenna input. A UG-636A/U will also adapt a BNC directly to the "unbalanced" antenna input.
The vacuum tubes originally had black, heat dissipating IERC tube shields installed on them. According to a study done by Collins Radio, this increases tube life by up to 53%. If your radio does not have them or simply has shiny heat shields which have been painted black, it might be a good idea to pick up IERC shields at a hamfest. The R390A uses three sizes, short 7 pins, regular 7 pins and regular 9 pins. These have gotten expensive of late as more and more tube enthusiasts realize their worth.
A couple of other "don'ts" come to mind. To keep the receiver stable, DON'T, turn on the "ovens" switch located on the back panel of the receiver. It causes the receiver to steadily drift in normal temperatures and can also cause the PTO to be irreparably damaged should the thermostat fail causing the oven to lock "on." Another tip: if the receiver is going to be left on but not in use, DO NOT use the "STANDBY" position on the FUNCTION switch. The now unloaded stages will cause the various voltages in the receiver to rise upwards perhaps beyond the tolerances of some critical components. This is caused by the multiplicity error in our sometimes 120v+ line voltage v/s the 115v in use when the 390A was designed and built. Since it is normal for the "LOCAL GAIN" control to not completely mute the audio when turned down fully, it is natural to consider putting the receiver in "STANDBY." Remember, DON'T. Instead, turn the audio down and also back off the RF GAIN control to about 11 o'clock and the residual audio will disappear and no damage will be done to the receiver.
One of the mods I install is a precision replacement pot used to zero the "CARRIER LEVEL" meter. It is located on the top of the IF chassis (chassis module behind the "LINE LEVEL" meter). To adjust it, let the receiver warm up for about and hour then unplug the antenna and tune the R390A to a dead spot on any band. Remember, the R390A is VERY sensitive and simply unplugging the antenna is not 100% insurance of completely removing a signal. Once a dead spot has been located, zero the "CARRIER LEVEL" meter with the presicion control.
The "IF OUT" connector on the rear of the receiver can provide an IF signal to the VERY EFFECTIVE, highly recommended, Sherwood SE-3 synchronous detector. An SE-3 and R390A combination are a "deadly" combination of classic tube engineering and modern technology. I have found that using the SE-3 MK3D, the operator is able to recover about 30% more useable audio from a given AM signal with more fidelity and far less distortion than the R390A alone. All of this, without the shortcomings of todays receivers using "modern," (cheap) engineering approaches.
Speaking of audio, supurb results can be realized by coupling the "DIODE LOAD" point on TB-103 located on the rear of the receiver to a Hi-FI amplifier. Simply obtain an audio extension cable with an RCA plug on one end from Radio Shack. Place a 470K resistor in series with a 10uf, non-polarized (also available at Radio Shack) capacitor and connect it to one of the screws holding the jumper across the "DIODE LOAD" screws on TB-103. Do not remove the jumper. Connect the other end of the capacitor/resistor network to the center conductor of the RCA cable then ground its shield to the "GND" screw located on TB-103 immediately to the right of the "DIODE LOAD" screws. Plug your cable into the TAPE or AUX jack on your stereo receiver, adjust the tone controls as appropiate and enjoy.
For EXCELLENT AUDIO, try tuning into the Venezualean Ecos del Torbes after local sunset on 4980. Open the "BANDWIDTH" to the 8kc position and enjoy some of the best hollow state audio you will ever hear!!!
Builders of the SE-3 MK3D and other useful items. I have personally had very satisfactory dealings with Bob Sherwood beginning in 1975 when I bought a modification package for my Drake R4-C. While the SE-3 MK3D is not effective in receiving SSB, I cannot recommend it highly enough for achieving top AM performance with the R390A.
The Hollow State News focuses on service and useability issues on receivers such as the R390A, Hammarlund SP-600 and HQ-180(A). Recently, Charles Talbot, K3ICH has offered a bound reprint compendium of all issues of the HSN. Contact him directly for information and pricing.
Charles Talbot - K3ICH
HSN $5 for a 4 issue sub. Back issues $1 each and as if 1/1/97, we are at issue #39. Make checks payable to: Ralph Sanserino.
Original manuals can be purchased from:
The NTIS Sales Desk is available between 8:30 a.m. and 5:00 p.m., Eastern time, Monday through Friday.
Sales Desk: (703) 487-4650
Mail Orders Send orders to:
Fax Orders (703) 321-8547
Fax service is available 24 hours a day, 7 days a
week. To verify receipt of your fax, call (703) 487-4679, 7:00 a.m. to 5:00
p.m., Eastern time, Monday through Friday.
Noted Electric Radio Author Bill Kleronomous, KD0HG will modify an existing R390A audio chassis to provide "hi-fi" sound backed with about 5 watts of push-pull power. As an added bonus, the 600/8 ohm audio matching transformer is no longer required. So, if you want to hear excellent audio from your R390A, consider obtaining a spare audio chassis and send it to Bill to modify. While not especially attractive for DX'ing, I can personally attest to the improved audio for the program listener. Contact Bill for current availability and pricing at:
Longmont Audio Labs
Yes, thats right. Cabinets! You can purchase top quality vintage-type metal cabinets which fit the R390A. These are even complete with piano hinge top covers! The best part is the price, about $125 for the "DCR" series cabinet as of 1997.
Premier Metal Products Company
While the CCA focuses largely on Collins' contribution to amateur radio products, membership can be helpful to R390A owners. I recommend membership in the CCA. Any person who has an interest in Collins Radio is welcome to join. Annual dues are $15 per year for those living in the US and $18 for Canada. This includes a membership certificate and the quarterly newsletter, The Signal.
Mail your remittence in US funds to:
The Collins Collectors Association
ER publishes a monthly magazine about the size and format of the current NASWA Journal. It is a very worthwhile publication and focuses entirely on tube or "hollow state" receivers and transmitters. Electric Radio is $38 per year mailed first class and $28 for 2nd class. Canada is $39.
Fair Radio has been around since 1947 and sells, among other things, R390A parts and entire sub-chassis. Their prices are, in my opinion, a little on the high side of reasonable but Fair has always given me excellent service.
Antique Radio supply caters to the hollow state enthusiast. They have a large selection of vacuum tubes and other goodies.
Antique Radio Supply
For those interested in listening to Shortwave Broadcast or Shortwave Broadcast DX'ing, NASWA fills the bill. They publish a monthly 60+ page bulletin with program schedules, features, DX listings and other S.L. material. NASWA is the oldest SWBC focused organization in North America. A sample bulletin can be obtained for $2 from:
This is the suite of vacuum tubes used in the '390A. It is a good idea to pick up at least 2 complete suites of tubes while they are still reasonably priced and even better to have 4. Make a few copies of this page and take it with you to the next hamfest. Always try and purchase the industrial tubes. These are the underlined numbers.
Total Tube Count: 26
As of this writing, tubes are not as difficult to find as some of the handwringers might say. On the other hand, the number of available tubes is finite so consider building a stock with the goal having at least 4 complete sets on hand. Also, always try and purchase JAN tubes. These are found in plain, white boxes, are labeled JAN and also show the date of mfg on the box. In the case of the 6BA6, 12AU7 and 6C4, try and purchase the 5749, 5814A and 6100 respectively which are premium tubes with JAN/Industrial specifications.
** NEVER, EVER INSTALL CHINESE OR RUSSIAN TUBES IN AN R390A
The R390A uses 5 different sizes of heat dissipating, black, IERC tube shields. Installing the correct type and part number shield can dramatically decrease the operating temperature and in turn, increase the life of the vacuum tubes. Collins addressed this back in the early 50's in service bulletin #303 which graphically compared the beneficial performance of various types of tube shields with not using shields at all.
The proper tube shields can easily identified. They are anodized black (or deep purple), have an open top with a series of tabs folded over a thin, octagonal metal tube inserted longways inside the shield. They are also plainly labeled "IERC." There is a unique model number stamped on the outside of the shield denoting which size it is designed to fit. Refer to this number when obtaining the shields.
Below is an inventory with individual quantities of the 5 different part number IERC tube shields used in the R390A:
Black tube shields labled "WPM" my also be found. While I personally don't feel these are quite as effective as the IERC design, they are far and away better than the shiny types described below.
Radios which still have shiny tube shields should have them replaced with the above IERC shields as soon as possible. Even if they have been painted black on the outside, these shields have no provision to grip the tube bottle and sink the heat away from it. Also, the bright inside surfaces of the shield actually reflect the heat back into tube and on to the dark internal plate structure which could cause the tube to over dissipate and shorten its service life.
Each R390A/URR that I rework has many hours invested in the electronic, mechanical and cosmetic restoration process. Each receiver is given a thorough general operational check before the restoration process begins and any problems or deficiencies corrected. Below is a brief, general checklist of what was done to this particular receiver. Other, specific items are addressed on a unit by unit basis according to need and may not be specifically noted here.
- General- Electronic & Mechanical
- Main Chassis Assy/General- Cosmetic
- RF Sub-Chassis Assy
- P.T.O. Sub-Chassis Assy
- IF Sub-Chassis Assy
- AF Sub-Chassis Assy
- Power Supply Sub-Chassis Assy
Prior to final Q.C., each radio is operated for a full 3 hours. This allows the unit to properly heat-saturate before a full alignment of:
EAC Mfg R390A #905
After completion, each radio is checked for sensitivity and general performance on significant bands used by the SWBC DX'er and Amateur Radio Operator. Below is a final post-restoration performance summary for this receiver.
Band Frequency 10db S/N + N Sensitivity (uv) 4kHz filter, AM
120M 2.2 MHz
90M 3.3 MHz
60M 4.8 MHz
49M 6.0 MHz
41M 7.1 MHz
31M 9.6 MHz
25M 11.8 MHz
20M 14.2 MHz
19M 15.2 MHZ
PTO End Point Error:
This R390A/URR Restored and Tested For:
Evaluating the performance of this receiver by listening to the amateur bands or the BBC is a little like looking across your yard with a telescope. You don't really find out much more than you already knew. Here are a few Shortwave Broadcast DX targets to try for. All are just a bit on the difficult side. The challenge just might surprise you and open up a whole new hobby segment, Short Wave Broadcast DX'ing.
All listings are by UTC time:
Because your BFO makes a great AM tuning aid, it has been carefully set up to help you perfectly tune a station. Ever wonder when a station is perfectly tuned and in the center of a filter passband? That is quite important for best audio recovery and lowest distortion.
Your R390A has 4 Military-grade Collins Mechanical Filters plus 2 crystal filters in the IF section whose center frequency is 455KC. I have optimized their center frequency very carefully during alignment. Additonally, the BFO has been precisely set to zero beat with a 455KC signal coming through the IF when it is set to "0" or center on the front panel scale. Here is how to use the BFO as a tuning aid:
Using this technique, the desired signal is centered exactly in the IF passband. You are assured of maximum audio recovery with the lowest possible distortion.
Remember, this technique is for AM only. SSB, a kluge
on the R390A at best, requires a different procedure.