>
>I'm back with another weird question.
>
>I find that on 10 Meters my SB-200 talks back to me. It repeats what I say
>as I say it. It sounds just like loose laminations in the modulation
>transformer of an old AM transmitter.
>
>What can be the cause of this and is it an indication of any serious
>problem?
Loose windings on the hv RFC. Try this: Pull power plug, wait until hv
is fully discharged. Remove cover, dip tip of finger in urethane
varnish, rub on windings of hv-rfc until you have a smooth coating. .
Let dry c. 1 hour. If it still talks back, go for an exorcism.
>As an afterthought, the input match on 10 Meters is terrible. I've been
>able to get the input SWR down to a bit over 3:1 by replacing the fixed cap
>with an adjustable ceramic trimmer. I would like a better match. Adjusting
>the coil slug makes no difference.
indicates too much L.
>I've searched AMPS archives and no one,
>it seems, has come up with a satisfactory solution other than using an
>antenna matching unit between the exciter and the amp. There MUST be a
>better way. Can anyone help?
>
To improve the input match for use with solid-state radios, increase the
Q of the tuned input. This involves decreasing L and increasing C-in.
Xc-in should be c. 20 - 25-ohms. C-out is best determined
experimentally with the amp. being driven to half or more suds. The
length of the coax affects the tuned inputs, so stick with one length.
cheers, Steve
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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