[Heathkit] HG-10 -VFO power supply, DX-60B

[Kevin Ward]

Whenever I see a TR switch built into a transmitter, I assume that whoever
added it did so in order to run QSK (full break-in).  To do that
successfully it is necessary to incorporate a (RF) gain reduction circuit
for the receiver.  You want full receiver sensitivity with the key up, and
an adjustable but reduced gain with the key down.  It's usually not
difficult to do, depending on what the receiver is, but without it the
transmit signal is just too loud.  It won't harm the receiver  -  it's just
LOUD!

As for the TVI issue, it is NOT always true that TR switch circuits are a
problem.  If the switch is built into a well shielded final amplifier, and
care is taken with wiring and TVI-proofing techniques, your rig will be
clean.  Many external TR switches have a gain of less than one, but a switch
connected to the plate tuning capacitor can provide a gain increase.  At the
same time, the transmitter Pi-network is in the receive signal path; the
transmitter final can be resonated without keying the rig.  The Pi-network
also adds some selectivity, in some cases actually preventing cross-mod.

If you want to try QSK and you're using a tube-type receiver, I'll be glad
to help you get it working.  Like Western Airlines, "It's the Only Way to
Fly."

Kevin  N2IE



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