Re: [amsat-bb] Re: AMSAT-BB-digest V2001 #460

[Jesse Morris <w4mvb@xxxxxxxx>]

Good Evening Dave and All,

Thanks for the info.  I think you may be right on the money with the
grounding pins.  Since I had blown the front end of my two units before I
received your kits, I had done some work in one of them, including
putting a MAR-3 in the front end.  I just used pieces of resistor (or
capacitor - I don't remember) leads for the grounding pins and I did not
do a very good job of placing them.  When I received the kits from you I
did not change the grounding pins on that unit and it is my "bad" one. 
As I pointed out before, I also butchered up the input link on it.  

When I had this unit up along side a Trans System 3733 I found the 3733
(with the stub cut) to be about 3 db better at weak signal detection than
the Drake.  Since that time I replaced the Drake with another 3733 and
found those two to be identical (and confirmed that the antennas were
also the same).    This afternoon I replaced one of the 3733's with my
second Drake and could not tell any difference between the weak signal
detection capability on one UO-11 pass.  Of course that's only one brief
test but I was encouraged.  The 3733 has about 4 db more gain but they
seemed to be equal as far as weak signal detection was concerned.  I had
no instability with the Drake I had up today.  One of my antennas has a
conventional  feed and the other has a W0OQC grounded feed.  The Drake
that I had up today was connected to the antenna with the grounded feed
but when I had the other one up it was connected to the antenna with the
conventional feed.

Incidentally, I have some sort of local noise here at a bearing of about
320 degrees.  I can't detect any type of signal signature - the noise
floor just rises when I point the antenna in that direction.  The first
time I had the Drake and the 3733 up the noise increased 10 to 12 db on
the 3733 and about 2 to 3 db on the Drake.  When I put up the second 3733
the noise increased 10 to 12 db on both converters.  I swapped 3733
converters between antennas as a test to evaluate the two antennas and
found no different in the performance or the mystery noise.  When I put
the other Drake up this afternoon there was still a 10 to 12 db noise
increase in the direction of the noise while the Drake showed only a
couple of db increase.  I am guessing that the noise is in the image
frequency range and that the filters in the Drakes are doing their job. 
I haven't put the filters in the 3733 converters yet.

Your mention of the 33 ohm resistor has given me the idea to play around
with that value.  I'm going to try a 100 ohm and see what happens.

Thanks for the info.  Hope to catch you on AO-40 soon.

73's de Jess - W4MVB   
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