I have made several measurements on the keying of several Icom radios
and the "hsend" line is timed incorrectly for the IC706 and IC7000 in
that it goes away BEFORE the RF does. The 746/756 type radios do not
have this problem. Please take a look at
http://www.bnk.com/w0qe/amplifier_timing.html for my measurements.
Phil & Debbie Salas wrote:
> 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
> 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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