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Further AIDC 3733 adventures



Finally had the chance to hook the 3733 to the test
equipment, and attempt to tweak the
comb/digital/interdigital filters...

Device: AIDC 3733, unmodified
N Adapter in place of dipole antenna

Input: Agilent signal generator, at 2401.0 Ghz, -100dBm
Output: Agilent Spectrum Analyzer, set to center on the
spike at 123.0243 Mhz

I tried turning each of the hex adjustment screws on both
filters but saw no appreciable effect on the scope. My
filters only had screws in two of the three holes. I moved
the center screw to the edge on each filter and tried there
-- no effect.

I'd have to conclude the filters are indeed broadly tuned.
We need to look elsewhere for solutions.

I found one interesting phenomenon. When I touched my finger
on the large screw immediately below the top filter, the
gain went up over 10dB. Now if we can figure out how to
reproduce the effect with a capacitor. Perhaps when cloning
becomes all the rage there will be enough fingers to go
around, but until then.......

As for the crystal. It is indeed temperature sensitive. At
rest, I measured the output frequency at 123.0243. When I
put my finger on the crystal and heated it up to body
temperature, the output frequency went up to 123.0268 -- a
swing of 2.5 Khz. Take the finger off and the peak slowly
retreats to 123.0243.

That's it until we get our (slightly incorrect) new crystals
next week.

73,
Art, N3OY


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