[R-390] Proper Muting

[rbethman]

Roy is entirely correct!

I run a BC-610 and an R-390A for AM operations.  I have a Kenwood SM-220 
Station Monitor with Panadaptor attached to the BNC connector on the 
rear of the R-390A.

Even with the use of the muting function AND an EF Johnson T/R switch, I 
have to keep the RF gain rolled back enough to prevent feedback into the 
microphone.  There is PLENTY of RF at these power levels.  I've also 
applied toroids on the mic cable, the muting wires, AND the coax from 
the T/R switch to the R-390A.

Bob Bethman - N0DGN

+-------------------------------+----------------------------------+
| N0DGN AMRadio Manassas, VA    |          Home Builder            |   
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| Bob Bethman                \\\|///     " The absence of a danger |
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|        2 BC-610s w/BC-614s, 2 R-390As - 1 Collins 1 Eac          |
|         Heathkit DX-60, Apache, Mohawk, SX-101, HT-32A           |
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Roy Morgan wrote:

> Notes:
>
> 1) The relay is operating on 6.3 volt filament current supply and uses 
> about 40 ma of current. One side of the circuit is ground.  The think 
> is in MUTE mode when the terminal 9 on TB 103 is grounded and the mute 
> relay is energized.  The MUTE relay is in the audio deck.  (The 
> Antenna relay is also energized at this time.)
>
> 2) The entire radio ahead of the audio amplifier stage is operating 
> normally.
>
> 3) The antenna connections (both UNBALANCED and BALANCED) are 
> grounded, but strong signals from transmitters will get through, as 
> Joe notes above.
>
> Roy
>
> - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> 7130 Panorama Drive, Derwood MD 20855
> Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
> roy.morgan@nist.gov --