[R-390] Modification?

[ToddRoberts2001 at aol.com]

In a message dated 10/18/2006 11:54:00 PM Eastern Standard Time, 
future212 at comcast.net writes:
Hello,

Saw this on Epay and was wondering if anyone knows what the mod is? It 
has inputs for 2 L.O.'s and a Sync. Th Ebay tracking number is 200037599271.

Best,
DW Holtman
WB7SSN

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