[R-390] Modification?

[Tom Norris]

On Oct 18, 2006, at 11:14 PM, ToddRoberts2001 at aol.com wrote:

>
> It looks like an R-1247/URR variant of the R-390A. These had  
> external inputs
> for the 1st, 2nd and 3rd Local Oscillators on the rear panel that were
> provided by an external synthesizer for high-stability operation  
> and were supposedly
> used by NASA in the Apollo space program. The radio can be tuned  
> like a normal
> R-390A without the external synthesizer. Several small relays  
> inside switch
> it over for use with an external synthesizer when needed. 73 Todd  
> WD4NGG

Yea, it's got the rear panel for it, and from the pictures there are  
some of the cables inside.  I wonder if all the "guts" for the rest  
of it are there?  Only the radio is collectable.  Used to be folks  
like Rick Mish would remove and toss the adaptors and other things  
that were inside.... myself, I have the synthesyser decks, but I'm  
not sure I'd ever use it either since you still have to tune the  
radio to frequency THEN tune the very noisy 60's vintage frequency  
synth decks.

Interesting thing, weren't the 1247's  (I apologize to Barry for the  
typo, I'm really asleep right now) normally later model radios?  The  
Manson radios I've seen looked to be 1967 EAC's - or at least later  
than what appears to be either a 56 or 58 Motorola (with an R-390/URR  
long tag to fill the empty space).

At least this one has the audio transformer problem solved, like  
what's been discussed here on the list.  Looks like there is one of  
the small 600:8 ohm can transformers mounted on a bracket just  
underneath the terminal strip behind the power supply.


Tom