[1000mp] (Non) Switching of RX Ant (was RX Ant Out)

[Bill Gode, Sr.]

Relay RL-1001 switches OFF on transmit, after being enabled from the RX 
ANT switch.  This reconnects the MP receiver to the normal T/R relay, 
where it is also disconnected on transmit.  The control circuitry is 
shown on the schematic.

You can hear RL-1001 switch ON when pressing the RX ANT button and you 
can hear it switch back OFF when keying the PTT line.  Placing an 
ohmeter across the RX ANT jack will show that the 100 ohm surge 
resistance to ground appears when the RX ANT button is pressed and 
disappears when transmitting, verifying proper operation of the relays 
to protect the receiver front end.

Bill, W9NHQ

Pete Smith wrote:

> Y'know, I think I was wrong about the Mark V front end -- it now appears 
> to me that only the transmit antenna is disconnected from the receiver 
> during transmit, and that any separate receive antenna remains connected 
> during transmit if the separate RX antenna has been selected, making 
> some sort of external protection almost mandatory.
> 
> Thanks, Barry, for making me take another look.  There's nothing like a 
> false sense of security to rear up and bite you.
> 
> 73, Pete N4ZR