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Drake Converter/AO-40



Good Afternoon to all,

I got my spare Drake converter going over the weekend and should have had
a pretty good look at AO-40 Monday morning but I couldn't drag my old
bones out to the driveway to set up the antennas at 6AM.   I did tweak up
my weak signal source and got some pretty stable readings while comparing
antennas on the "driveway antenna range".  I could not detect any
difference between the grounded feed helix and the ungrounded one.  I had
a left hand ungrounded model and it also was the same. I was a bit
disappointed in the comparison with a 1 lb coffee can horn however.  All
three antennas (21 turns each on 1 inch PVC) looked to be only about 4 to
5 db better than the horn.  I know I built that coffee can antenna
according to someone's data but I can't remember the details and I can't
find the reference.  My probe seems to be a little bit longer than one
quarter wave and the can seems to have a bit of a squint.  Can someone
tell me where the probe should go in the coffee can and approximately
what the gain should be?

New subject - After removing the two coils and SM caps in the Drake
converter IF circuit, I measured one of the caps on a hunch.  It seemed
to be about 20 pf.  Before I could confirm the reading I knocked the
piece of paper the caps were on to the floor and I could never find them!
 My thought was that they would probably work in parallel with the two
caps in the series IF circuit to improve the bandpass below 200mhz.. 
Maybe someone else can confirm the value of these caps.

I think I have a few days before I get another really good look at AO-40
so I may get some additional antenna comparisons completed.

Thanks for any info on the coffee can horn.

73 de Jess - W4MVB

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