I doubt that the problem is hot switching. Emtron sequences the relays on
their QSK board and I use MicroHam's software router and MKIIR Box which has
additional sequencing.
I've received many responses indicating that this is not an uncommon problem
with vacuum relays. One suggestion was to use 120VAC and a 75 watt light
bulb through the contacts to clean them. Others who use QSK say they only
last a couple of years. Others say there is a quality issue with some
brands.
The relay in the 40M amp has become so cathodic that it is acting like a
detector and rectifying loud signals. Banging the chassis stops the problem
until the next T/R cycle.
I tried running 200W of exciter power through the N/C contacts on the 40M
and 20M amps. It appeared to help the 20M amp, which just started being
intermittent in the CQ WW CW contest. Emtron is sending me a new QSK board
for the 40M amp. Rudi also says he now uses only Jennings RJ-1 relays now.
Stay tuned.
Tom Taormina, K5RC
Virginia City NV
Tom,
I don't completely understand either, what the others have said as to why
the receive contacts
would be intermittent, even if there was a sequencing problem, because it's
a different set of
contacts, isn't it?
But on the subject of sequencing. if you happen to be using FT1000MP rigs
(the only one I am
familiar with so far) there is a menu setting for delaying rf after the key
closure. In my
case my vacuum output relay was switching in about 12 ms after the
transceiver gave
it the key signal, so I delayed the MP by 15 ms. Others have said vacuum
relays should
close in the 3-5 ms range, and if I could get mine to do that I would be
able to shorten
the delay and maybe get away with QSK.
Do you have a dual channel scope to make the timing measurements with? It
would be
interesting to see if Emtron is sequencing them properly, but even if they
are you
still don't want your driver slamming it with RF before that time is
complete, even if it
is 3-5 ms. Someone told me an Icom 756Pro III did not have an adjustment,
but I
haven't confirmed that.
Rick K2XT
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