Topband: Detuning TX ant + QSK

Richard (Rick) Karlquist richard at
Wed Nov 28 10:02:52 EST 2018

On 11/28/2018 5:18 AM, John Kaufmann wrote:
> Jim,
> I use Gigavac GH-1 vacuum relays for detuning my TX antennas when receiving.  The contact closure/release time is 6 msec.  You have to dial in enough QSK delay in your radio so that you don't hot-switch the relays.
> 73, John W1FV

A quick note on the GH-1:

1.  In theory, there is no limit to speeding up closure.
OTOH, release can only be speeded up to the extent of collapsing
the magnetic field by omitting the usual reverse voltage
protection diode.  After that, the mechanical response

2.  This works neatly with the GH-1 being energized on
transmit, where you want the quickest response.

3.  The limiting factor to speeding up this model is
contact bounce.  You can only apply a modest amount
of speed up before you are limited by contact bounce.
With other models, of course, YMMV.

Rick N6RK

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