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AO-40 Reception



Good Morning ,

I had a chance to do some additional side by side comparisons between the
Trans System converter with the stub cut out and the Drake with all the
G0MRF mods today.  The Trans System converter with and it's antenna
continues to be better.  By using a step attenuator in the IF line I was
able to estimate that the Trans System was about 3 db better at weak
signal detection than the Drake.  The Trans System has about 5 db more
gain than the Drake but that did not prove to be a factor.  They both use
a 21 turn helix with the W0OQC grounded feed but they are not identical. 
I am a little mystified by the difference since I could no detect any
difference in the antennas or the converters during ground testing before
I put them up.  I have an additional Drake converter with all the mods so
I am going to try to put it up with an antenna that is identical to the
Trans System and see how that works out.

I am encouraged with my results of the past few days.  I was able to work
VE3NPC and W0OQC this morning at a range of 62K and squint angles of 16
to 18 degrees although signals were very close the noise.  There were
brief periods when signals would rise pretty significantly but then fall
back.  I could always find and hear my downlink over a period of about 3
hours starting at about 1030Z.  As time went by the squint angle
decreased but signals did not come up here as the elevation also
decreased at the same time.  I was amazed at how much noise I received at
some places on the horizon as compared to a high elevation angle.  The
noise in the Drake that I, and others,  have experienced from time to
time seems to be in the converter.  At least I don't hear it with the
Trans System.  I starts suddenly and stops suddenly and some days I don't
hear it at all.  I don't see how it can be any sort of rf oscillation
with the symptoms I'm hearing.   I guess it could be something getting in
to the IF and not getting into the Trans System.  It sounds somewhat like
rain static but there doesn't seem to be any pattern to it's appearance.

As others have pointed out here, the name of the game is squint angle.  I
don't know what the beam width of the current antenna is on the bird but
I feel sure that with a lower squint angle the single helix will do the
job with a good converter.  Of course it wont compete with the dish
antennas but it's fun to try!

73 de Jess - W4MVB  
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