[ARC5] A discussion on AGC.

[J Mcvey]

Neither the SCR-274 nor the ARC-5 receivers used AGC to accomplish muting during transmit.They used relays in the rack to switch the headphones to the modulator output.. Yiu get voice monitoring off of the modulator secondary in voice mode, sidetone form the modulator in CW.
The only "muting" is done in the T/R relay assembly where the receiver antenna is grounded during tx.Howevr there is more thna enough leakage to monitor the CW on the recievers if the modulator plug is disconnected. Voice will have unacceptable feedback.i had to use the rack relay system because of this . I installed a 'spot switch' to interrupt the the relay line so I can monitor the TX directly when QSY.
 

    On Tuesday, May 9, 2017 3:57 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
 

 Receiver muting may be a topic closely associated with the AGC line.The AN/ARC-5 receiver may have developed overwhelming AGC voltage that effectivelysilenced it while transmitting, but this doesn't seem to be addressed by the AN/ARC-5manual.
It's not clear from the SCR-274-N manual how, or even whether, muting was achieved.
Ken mentioned that the cathode wiring of the RF amp and 1st IF amp of the SCR-274-N
are wired together, and I believe they are connected to the RF gain control so that theoperator/pilot could adjust the level to suit his preference, but this leaves open thequestion of how he could deal with hearing his own transmissions in his headphones.
I'm curious to know more about muting and how it was achieved in the ARA, SCR-274-N,
and AN/ARC-5 models.
73 de Neil ZL1ANM
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