Tom Rauch wrote:
>
> > 2. use the SWR alarm relay to apply cutoff ALC voltage to the exciter;
> > this method protects the amplifier's relays, so it's better than just
> > de-keying the amp.
>
> If the relays in the amp are properly sequenced, dropping the relay
> line won't hurt a thing.
By 'properly sequenced' I presume you mean that the output relay closes before
the input relay and opens after it. But even in this case, dropping the amp
relay line hot-switches the input relay. I am afraid the 50-100 watts from the
exciter could damage the small input relay.
The exciter PTT line is another story and might be OK. In my case, I operate
full break-in CW with the internal keyer in my exciter, so there isn't an easily
accessible 'ptt' connection. I intend to find a more foolproof way of quickly
shutting off the output of my exciter.
Interestingly, the other day I was testing a 160-meter antenna with a remote
tuning device in which I had underestimated the required spacing for a
capacitor. It arced, causing the swr protection circuit to actuate. The arc
lasted much longer than I liked! I think the problem is that the VFD uses a PIC
(or something) to compute the SWR, and that this circuit takes a long time to
actuate. So I'm not sure any more that this is the ideal type of protection
device -- a simple directional coupler with a DC-amplifier would be a lot
quicker.
73,
Vic, K2VCO
Fresno CA
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