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Re: Drake instability & Dielectric Filter Simulation



Hope you find a solution as I have the same problem with mine.

Jesse Morris wrote:

> Hi Bill and All,
>
> I can confirm that the noise that I (and others) have encountered with
> the G0MRF modified Drakes is indeed instability.  My tests have not been
> nearly as detailed as yours but I have been focusing on the amplifier
> input circuit.  I have two units and one is worse that the other
> (naturally it was the one I had put up to test).  Both of the units seem
> to be sensitive to input terminations.  As long as I have a good antenna
> on the good one it seems to be OK.  I only notice the problem with it
> when I use a dipole that I built into a BNC connector on it and I move
> things around near the antenna on the bench.  I destroyed the input
> hairpin on the bad one during a repair before the modification and I
> tried to rebuild it with a small piece of wire.  Since I got it back down
> off the mast I have played around with a short loop of wire on the input
> and have noticed some improvement although it now has a bout 4 db less
> gain than the other one.  I had the test dipole on the bad one yesterday
> and it was oscillating like mad unit I put a 6db pad between the antenna
> and the converter and then it settled down.
>
> I still have some tests to run but I can't seem to get back to them.
> Thanks for posting your results here.  I'll do the same when I have more
> info.
>
> 73's de Jess - W4MVB
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