[R-390] What is the difference between 390 and 390A

[Flowertime01 at wmconnect.com]

I have heard of some WWII receivers that were specially built to minimize
the osc leakage through the antenna input for the reasons you mentioned, the
National brand comes to mind but I could be mistaken.

John
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Folks,

The Army Security Agency was happy to couple bunches of R390 and R390/A 
receivers to the same antenna. The favorite antenna was a rhombic. The favorite 
antenna coupler to spread the signal around was a CU872. Local oscillators 
radiating grief to other receivers was a real nono. The R390 and R390/A will work 
and play well with any other thing that glows in the dark. Some solid stuff is a 
bit uppity but its the solid stuff not the warm and glowing items fault. The 
Ops ran rooms full of the receivers and you would never know there was another 
oscillator any where except that single signal you were working. R390 and 
R390/A just do not leak.

Roger KC6TRU