The R-390 Page
I'm not really a R-390/R-390A nut, but I can't help but admire the incredible engineering in these radios. I hadn't heard of them as a kid. I guess this is because they were classified (!) until 1968 (!!). I am told that the Pueblo that is still somewhere in a North Korean harbor has a number of these units aboard.
There is a document floating about the web that is an engineering report on the construction of the R-390 and the R-390A. This is quite remarkable. Generally there is nothing left of a radio but the unit itself. It is quite rare that any information from the engineers actually survives. This document refers to two articles - one from the GE review and one from the Proceedings of the IRE. I scanned these two articles in for the interested parties (if any). They are both written by engineers for engineers, but it gives you some real perspective as to how things were done then. Those charts were intended for use by engineers that are designing radios. The engineer would place a straight-edge on the chart and read off some of the design parameters. Today, this would take 2 seconds in MATLAB. I typed in the equation and produced a copy of the chart in about 10 minutes. The original author probably spent weeks bending over a Marchand calculator (the original "one-armed bandit") grinding out the numbers that went into those plots.
Scanned R-390 Related Literature
There is more-than-abundant documentation on these receivers floating around, so I am just adding here things I haven't seen elsewhere, starting with a couple of engineering reports that were reportedly used in the design of the R-390. |
| Download 6MB |
"Aids in the Design of Intermediate-Frequency Systems", Paul C. Gardiner and J.E. Maynard. From the Proceedings of the IRE, November 1944, pp674-678. This article refers to the next one as its basis. The origin of the "stagger-tuned" IF of the R-390 is in this article, although it isn't called that (p677, near the end of column 2). |
| Download 10MB |
"Tuned Transformers" J.E. Maynard. General Electric Review, October 1943, pp559-561, and part two in November 1943, pp606-609. I must quote you the first sentence of this article: |
| Download 18MB |
This is a different scan of the Army manual for the R-390 (NOT the R-390A). It is TM 11-5820-357-35. You can get a cleaner copy of this from LOGSA at LOGSA SITE. You have to fiddle around a bit to get the document you want, but eventually you can get access. The problem is that the schematics in the one from LOGSA are illegible, but the text is great. This one is a more funky scan that has been floating around for a while, but the schematics are quite readable. The schematics are scanned in 8.5x11 pieces. |
| Download 18MB |
This is a different scan of the Army manual for the R-390A. |
| Download 180MB |
TM 11-856 Radio Receiver R-390/URR. This is my own high-resolution scan of the original R-390 (not R-390A) manual. I include in the beginning three of the four field changes (anybody got a copy of change order #3?). There is something different and unique about this manual versus ALL other R-390/R-390A manuals - this is the ONLY manual of this receiver family that has wiring diagrams for every single module in the receiver! This copy has the manual and the schematics in their original form. |
| Download 10MB |
TM 11-856 Radio Receiver R-390 Field Change Orders C1, C2, and C4/URR. This is my own high-resolution scan of the original R-390 (not R-390A) field change orders. I include three of the four field changes (anybody got a copy of change order #3?). This is just the field change orders. There is one illustration, which is the gear train breakdown detail. I include it both in original form and in 11x17. |
| Download 180MB |
TM 11-856A Radio Receiver R-390A/URR. This is my own high-resolution scan of the original R-390A manual. This copy has the manual and the schematics in their original form. |
The Great R-390/R-390A
Salvage Expedition
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Here is the "great wall of receivers." There are about 60 receivers there, of which about
20 are R-390 (that is, not the R-390A). It appears that of these, 5 or so can be easily put
into good working condition and maybe 20 more can be restored with some amount of trouble.
I am told that they originally came from Anchor Surplus, which is long-gone. Many of the
modules are just dirty, or have rusty cans. There are oodles of every kind of module - and yes, lots
of IF strips with four mechanical filters. I have not gone into them yet to see how many
are in working condition, but there is no shortage of them.
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Here are a couple of units that are in good condition. I think with a bath and a few modules, these will be good working radios. There are some specs of rust here and there, but the gear train turns smoothly without binding. |
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Here are a couple that are in pretty sorry condition. The main tuning knob on the bottom one is terribly pitted and the bristol screw that holds it in is frozen. It appears to have been left out in the rain (sigh!) for some time. The gears do move a little bit, but will require a complete teardown to be useful. Hard to say at this point if much can be salvaged from these. Curiously enough, the front panels will look pretty good after stripping and repainting. They are not scratched, but simply faded. |
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These bins have some of the modules I have taken out and separated. There is a bin for R-390 PTOs, one for R-390A PTOs, several full of IF strips, others with audio/power modules. At the bottom there are stacks of transformers for both 390 and 390A. These all must be older units, since only a few have silicon rectifiers installed. There are two bins of nothing but front-panel knobs. One bin of IERC tube shields, and so on. |