[R-390] I'm back AKA R-390(XC-2)/URR

[Mike Peace]

John,

Good to hear from you, and glad the radio made it home.

Short answer: you've got something very special. That contract number,
W36-039-SC-44552, is the original Collins development contract for the
R-390. Under it, Collins built only three R-390 prototypes for the Signal
Corps at Fort Monmouth before any production radios were made:

  R-390 No. 1 — January 1951
  R-390 No. 2 — September 1951
  R-390 No. 3 — February 1952

The "X" in (XC-2) means experimental. Your plate says Serial No. 2, so you
almost certainly have R-390 No. 2 — the second R-390 ever built, delivered
to Fort Monmouth in September 1951.

That's a museum-grade radio. It pre-dates the entire production run.

Before you do anything else with it, take a lot of photos — inside,
outside, the data plate, any paper tags, any handwriting on the chassis.
Don't clean anything off. The little details on a prototype are part of its
history.

The primary source on these three radios is the Collins Final Engineering
Report (CER No. 297), here:


https://www.collinsradio.org/wp-content/uploads/2012/04/R390-CER-No-297-Signal-Corp-Final-Eng-Rpt-Includes-R-389.pdf

And contract background is on r-390a.net:

  https://www.r-390a.net/faq-manuf.htm

If you post some interior photos to the list, several of us can help you
figure out exactly what's original and what isn't.

Quite a find, John.

Glad it followed you home.

73,

Mike Peace VK6ADA
r-390a.net Administrator

On Wed, May 20, 2026 at 3:39 PM John Flood via R-390 <r-390 at mailman.qth.net>
wrote:

>  Greetings,
> After the  stroke i had 3 years ago and selling off all of my
> R-390,R-390A,R725,and R-392's that I had because the weight exceeded what I
> was allowed to carry.,. one of the radios i sold followed me home from a
> flea.  Forgive me if I asked this before, the brain is quite dusty, This
> unit has a phenolic tag from Collins R-390(XC-2)/URR Serial No. 2 Order N.
> W36-039-SC44552.  Does any one here know what the XC-2 mod was?  The owner
> had a great laff when I asked him about it...  He said you should know you
> sold it to me!    I do recall that now and told him I must have told you!
> At least i had the stroke as an excuse!  Well needless to say with the help
> of my son. the beastie is now inside my shack  Now starts a mission to
> again figure out what's so special about this one.
> John Flood  N1JAF
>     T email list: QSL.net - Donate Site
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