> Question is for routine SSB (and some occasional CW) does
> one really need an
> optoisolator circuit controlling a relay rather than just
> a lowvoltage power
> source plus a well rated (250vdc 2a) low voltage relay?
The problem with a relay keying another relay is activation
times are added. Whatever small relay's time you add in, it
makes an already poor situation worse.
Say you have 13mS on the large amplifier relay and 5mS on
the small relay. Pull in would now require 18mS.
Virtually all rigs actually output RF before the antenna
relays can transfer in an external PA. This can cause
amplifier bandswitch or tank component arcing or damage,
annoying pops or clicks up and down the band, and chopping
of the first part of transmission at every VOX or key
closure if you are not using push to talk or manual transmit
switching.
With a solid state buffer circuit you don't add the time of
another relay.
It does not take a special expensive circuit to do this or a
high speed relay. All it takes is one or two transistors, a
resistor or two, and a diode. You can also use a very fast
external relay, like a HV reed relay, but you have to watch
voltage and current transients.
It might be less time and worry to buy one. Ameritron also
offers a relay buffer. But they are easy to build.
73 Tom
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