Re: [amsat-bb] 2.4 Ghz Helix Match

[Jesse Morris <w4mvb@xxxxxxxx>]

Hi Mike,

I did use the DC ground match that W0OQC developed after I blew the
GASFETS in the front end of 2 Drake converters during testing.  I found
them to be just about as good as the conventional match.  The
conventional match might have been a half db better but that's really
inside my measuring capability so for all practical purposes I found no
difference in performance.  I did find the grounded match a little harder
to adjust physically however.  If I didn't  get the bend on the end of
the matching strip just right to start with it was physically hard to
change it (I was trying to use a "cup" at the reflector at that time). 
With the conventional matching strip which was anchored to the coax
connector at one end I could just slide the helix winding along the PVC
boom to obtain a null on the bridge and then set the winding in that
position with RTV.  I also started using a DEM preamp which is DC ground
so I really didn't need the anti-static protection of the grounded match.

I've just completed one of the DSP-10 digital transceivers described Bob,
W7PUA in QST a couple of years ago.  Among other things, it has some
really nice measurement tools.  I would like to repeat the whole process
again and see if I couldn't quantify some of my results a little better
but you know how those things go.  I may never get "round-to-it".

73 de Jess - W4MVB

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