[Hammarlund] HQ140X Receiver Muting & Standby

[Rodger Singley]

Ray,

In stock form, the terminals of the standby switch are in parallel with the relay socket.  With the switch in standby and nothing connected to the relay terminals, B+ is removed from the mixer, first IF, and AF preamp stages to silence the receiver for transmit.  For use with a transmitter, connect a normally closed set of relay contacts on the antenna relay so that the B+ connection is broken during transmit to silence the receiver.

I don't like switching B+ for standby and I modify receivers like this one to use the RF gain control bus for standby.  To do this, remove the B+ wiring from the relay socket and with an insulated jumper permanently connected between the leads that were connected to the two terminals of the relay jack.  Then install a 10K resistor between what is currently the grounded end of R40 and ground.  Connect a lead from the junction of R40 and the added resistor to one side of the relay jack and a jumper to ground from the other side of the relay jack.

You will still use a closed on receive contact from the antenna relay but now it will put the receiver into standby by biasing the receiver gain bus off instead of switching B+.  A variant on this technique is to use a 10K wirewound pot configured as a variable resistor in place of adding a fixed 10K resistor and this will provide a variable gain control during standby allowing the receiver to function at reduced gain as a CW keying monitor.  The Hallicrafters SX-88 and a few other receivers are already configured this way to act as a monitor during transmit.

Rodger WQ9E
________________________________
From: hammarlund-bounces at mailman.qth.net <hammarlund-bounces at mailman.qth.net> on behalf of Ray G3XLG via Hammarlund <hammarlund at mailman.qth.net>
Sent: Tuesday, December 5, 2023 9:29 AM
To: hammarlund at mailman.qth.net <hammarlund at mailman.qth.net>
Subject: [Hammarlund] HQ140X Receiver Muting & Standby

The Front panel has a switch for Receive/Standby and the rear panel has a
connection marked "Relay".

What relay is this referring to, a muting signal from the TX via a relay or
an Antenna change over relay?

How do I wire the HQ140X to Mute or Standby when using a Transmitter please?

73 Ray G3XLG

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