Thanks all for the excellent advice and links on T/R relays and switching
times. A wealth of knowledge.
That fascinating thread has perhaps delayed the day when I either rig-up a
test circuit to check why my TS850+LK550 eats Jennings relays, or "just
spend another $30" as someone put it. I must be on my 4th relay now (MTBF =
2-3 years) and noticed it sticking towards the end of WPX SSB this morning -
hardly an onerous job for a QSK-rated linear I'd have thought. Reluctantly,
I've long since given up using proper QSK on CW as that just seemed to
hasten their demise, though I miss that spooky sound of my own backscatter.
I'm still wondering what the actual problem is though. The key symptom is
low receive signals that can be normalised by clunking the PTT a few times,
until that kludge eventually stops working, generally a the very point when
some juicy DX multiplier finally comes back to me*. I've heard that low
currents on the receive side may be to blame, although these are vacuum
relays and should presumably be sparkly clean inside. Would it be worth
running "a bit of current" (my version of ampacity!) through the RX side of
some of the dead relays still lurking dejectedly in the bottom of my junk
box, do you think?
Or here's a more radical idea: I could change the relay over from normally
unpowered to normally powered maybe, to put the main TX RF through the other
set of contacts, then swap 'em over every year. Mmm.
Or, before anyone says, should I just build bigger and higher antennas to
steal a few more [femto]amps from the ether?!
* Of course, with next to no receive, I can't tell for sure. It's just a
waking nightmare really, a contester's version of Sod's Law, itself a
British version of Murphy's (see http://www.murphys-laws.com/ - there, I've
repaid the link debt).
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