I found that the drift in my Omni C was due to
temperature changes on the varicap diodes used for
RIT/XIT and band offset. They are in the circuit all
the time even if the RIT/XIT is off. With these diodes
disconnected the PTO was rock solid. I never did
around to try compensating for this as I got a good
deal on an Omni V and sold the C.
73, Dave, VE1ADH
--- Clark Savage Turner <csturner@slonet.org> wrote:
> An old topic, I remember this being discussed, but
> can't find my old
> notes. Anyone have a few hints or suggestions to
> slowing down the drift
> in my Ten Tec PTO? I have rebuilt it, the drift is
> over 1 KHz in an
> hour and it continues, but slows down, for many
> hours. I suspect I need
> to change the temp compensating cap in there and I
> have a friend with
> many boxes of temp compensating caps I can use to
> try.
>
> Has anyone chosen caps for their PTO and has any
> simple, basic advice
> that would help me? I am not trying for perfection,
> I just need a few
> hints to get down to 20 or 40 Hz drift after a
> little warmup, like my
> other PTO.
>
> Any tip at all appreciated. I have a freq counter
> and plan to tack
> solder in the replacement caps, then take some data
> and see where I get
> after a few tries. Make sense?
>
> Clark
> WA3JPG
>
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