Mike has good advice.
Here's another way to do that test if you have a manual tuner. Tune the
antenna with another radio on 20m. Then connect the Omni D. If it won't
show the same SWR, then you know the radio has spurs. And if the OMNI D
shows output on a separate SWR meter while connected to a dummy load and
with the drive turned down, it has a spur. The SWR should not change
with drive up on a dummy load but it will through a tuner.
Beside oscillation there are less common possibilities like messed up
band pass filters because of trimmer capacitors that have gone open at a
sliding contact, a broken coil winding wire, or bandswitch shaft that's
been installed with a wafer or two on the wrong position or bandswitch
contacts that aren't making connection.
In two models of Kenwood, they will oscillate on 10, 15, and 20 if the
RF board mounting screws aren't tight because they depend on those
boards for grounding. I think Tentec boards can also depend on the
mounting screws, so its a good check to simply tighten them. Some take
the screws out one at a time and add shakeproof lock washers to get a
better bite. That may last longer than just the screw, but since plastic
flow under pressure, board mounting screws do need tightening every few
years even with shakeproof lock washers.
And in Tentecs, dirty cable connections have been know to cause odd
radio performances. If the grounds were not good on a driver or PA board
on both ends it might oscillate where the gain was highest. So a bit of
DeoxIT (quarter drop) per pin and sliding the connectors off and on a
couple times sometimes cures ills.
73, Jerry, K0CQ
On 9/10/2010 9:49 PM, tubsc66@aol.com wrote:
> Thanks so much for the advice Jerry. Im fairly new to Ten Tecs and the
> older Omni's in
> particular. I realize my problem sounds unlikely to most people, but it
> is there... I just
> wondered whether this was a new twist I wasnt aware of, have a great
> weekend!
>
> 73,
>
> Chris KC5IIE
>
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