[Elecraft] KRX3 aux protection: good idea?

Franki ON5ZO on5zo at telenet.be
Thu Jan 24 06:38:30 EST 2013


Hello folks

My KRX3's carrier operated relay is rattling when I have an RX loop connected to its aux input when I transmit on 160/80. Too much antennas on a too small lot. Nah, Whadda ya gonna do?

As a quick fix I used an A/B antenna switching relay to open the RX chain when TXing. Loop on input A and switch to unconnected input B with PTT. But this QRO relay is very noisy to have it clicking away in the shack. With the box on the desk, I even feel it switching. So I'm going to make a silent dedicated solution for it.

Would the following idea have any side effects or negative consequences? I'm planning to use a DPDT relay as follows:
when in RX: NC contact in series to pass the signal, NO contact parallel over the input
when in TX: NC contact in series opens and blocks the signal, NO parallel over the input closes thus the RX is short circuited to GND. Or would a 50ohm resistor over the input be better than a pure short (seen somewhere on the web)?

Would this work? I can't see why not. Would any other stuff be needed or recommended (diodes, caps, MOV?) for RX protection?

All input appreciated. TNX / 73
Franki ON5ZO


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