>The single relay switches the antenna between TX and RX but also removes the
>cutoff bias from the tubes.
Greg, You are really on to something here, very interesting.
Your message is very timely because I am working on just that same
scenario in my homebrew amp. So far I have measured the vacuum antenna
relay, the input relay and the times in the FT-1000 MP transceiver. I've found
the vacuum relay switches in 10 ms, the input in 3 ms, and the transceiver
keying line to the amp goes low 2 ms after the cw key is closed. Now the
interesting thing for me was that the Yaesu has a menu function where I
can set the amount of time after the key is closed before any RF is delivered,
and it works, and it is very accurate. So I now know I have to set it to
at least 13 ms to protect the amp. The last relay to measure is the one
that switches cathode bias, like you mentioned, but at least now I know what
I am looking for. Then I have to tackle the issue of what happens on turn-off.
Haven't thought about that yet.
W8JI has some info on his web site, but I couldn't understand how or why he
was triggering his scope the way he did so I cluged (sp ?) up a little 555 to
give
me a nice sharp triggering pulse and an adjustable on-off time to key the
rig with. It transmits 160 ms and receives for 840 ms. So then I can move my
scope channel probe B to any relay and see the timing relative to the input key
closure. It works great. Zero cost.
Oh I might mention, I am able to do this fun stuff due to the generosity of a
guy who gave me a beautiful dual channel scope, which also has enough
bandwidth to see the rf envelope which my old tube scope couldn't do. He
reads this reflector so I know he's smiling right now. Thanks Old Buddy.
Rick K2XT
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