> 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.
If dropping the input relay causes a problem, you have the wrong
input relay. Probably half of the exciters in use today hot switch
the relays in PA's.
It's time to spend an extra couple dollars on the input relay if it
can't take hot switching 100 watts or so on occasion! It certainly
won't be reliable under normal use, since it is required to open first
and close last in normal operation.
> 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.
Sounds like a poor system to me also, depending on how busy the
PIC is and how fast it is. You'd not only have all the customary
analog delays, digital processing time (in worse case time) would
be added. That would include A/D conversions as well as the micro
looking at the data and outputing a control signal.
73, Tom W8JI
w8ji@contesting.com
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