On Nov 22, 2004, at 8:17 AM, Pete Smith wrote:
I do not use this amplifier QSK,
Pete -- With modern transceivers, there is usually no timing
difference between QSK-CW and SSB-VOX.
and have it set up with a speed-up circuit in any case. Normally, I
run 20-30 Ms of PTT delay to protect the relays, but that's not really
practical with hand keying. I may have been doing some hot switching.
The output relay is an HC-1
Thanks for the confirmation.
73, Pete N4ZR
At 10:34 AM 11/22/2004, R.Measures wrote:
On Nov 22, 2004, at 7:02 AM, Pete Smith wrote:
I modified my SB-220 about 5 years ago with vacuum relays on the
input and output. It has had a lot of hard contest use since then
without incident, but this weekend, after about a half hour, I
noticed that I was intermittently getting no output from the amp,
even though the transceiver looked like it was putting in normal
drive. It seemed to change from one switching cycle to the next --
sometimes it would go a dozen QSOs with no problem, but on the 13th
nothing was getting out.
About an hour after this started, the input relay (a Hi-G d'Italia
surplus job) started not closing intermittently, leaving me with no
drive either, so I shut the thing down altogether.
I have replacement relays on the way, but would like to tap the
experience on the list -- does this sound like just contact failure,
Yes, Pete. A vacuum relay equipped amplifier that is used with a
modern transceiver is at risk of hot-switching if it does not make
faster than the transceiver. Cu-contacts are especially vulnerable
to erosion from hot-switching. Since modern transceivers typically
begin to produce RF in 5 - 8mS, only a few vacuum relays are capable
of switching fast enough -- and even then, a speed-up circuit is
needed to initially overwhelm the L in the relay's coil.
Satisfactory relays for this job are the Jennings RJ-1A and the
Kilovac HC-1. In order to get enough speed-up, 3 - 5x the coil V
needs to be available during make.
http://www.somis.org/D-a-07B.jpg
...
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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