A little more info on vacuum relays (and other) QSK switching. I've been
playing with QSK switching for a little while now. I built an external
vacuum relay-based switch (see February QST), as well as an internal QSK
relay system for my ALS-600.
I've found that there are several transceivers that disable the amplifier
well before the RF output has decayed to zero, which causes hot-switching of
the transceiver output. This is usually not too bad of a problem as the
power has at least partially decayed when vacuum relays or high-speed signal
relays are used - but more of a problem if PIN diodes are used. But it is
certainly not good for the relays and transceiver - or the amp if the relay
sequencing isn't properly designed. And, at the very least, it causes key
clicks.
This is not a problem on my Elecraft K3 or Yaesu FT-1000MKV. But I've
measured the problem on IC-7000 and IC-706 transceivers. And I've had the
problem reported to me that this also occurs in Omni V andf Omni VII
transceivers (but no problem with Omni VI transceivers).
Folks always talk about the need for fast enabling of the relays to ensure
they are fully engaged when the RF is available. But it is important to
DELAY the relay drop-out until after the RF decays to zero if a transceiver
disables the amp too fast.
Anyway, this is something you might want to look into if you have a QSK amp
or external QSK switch if you have an oscilloscope.
Phil - AD5X
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