[Moon-Net] 2M antenna matching Data

Curt Nixon radio.ku8l at gmail.com
Tue Nov 8 15:44:27 CET 2016


Thanks for all the comments and directions folks:

Regarding the data and its presentation, I can only say I copied it 
directly from the dispaly on the software utility.  Some of it I 
understand, and some not so much.  I am a newb with the Smith chart.  
The software is a data sampling and control utility for the T100.  It 
collects sweep samples over a range of frequencies and step sizes and 
loads them to a CSV file.  They are then used to plot a smith chart as 
well as an SWR, RL, and R+Jx charts.

I believe the G is for Gamma which is (I think) the 50 ohm Smith 
normalized values of ZL.   I also think the "angle" shown is the angle 
of the vector at the given frequency and as the G point approaches 0+J0 
the angle becomes meaningless due to the minimum sample resolution  (25KHz).

Anyway.  I have been using these two antennas for 2+ years and yes they 
are as near identical as my machinist skills (substantial) could build 
them.  The T match jumpers are at the ends of the T bars as someone 
suggested.

They are oriented in the proper phase, and I cut the jumpers to less 
than +- 1/16" from same pc of LMR-400 Brand new.  My divider is one of 
the 1/2 WL  (1/4 +1/4) from square tube

THey system has about 28 initials on it but perhaps I am still expecting 
too much from the pair.  During the first period of the ARRL weekend 
past, I could not detect a single station, including the mega stations 
which were operating.   Even when they worked, stations rarely had a 
hard time detecting me, but I can barely  see a trace for them.  System 
still shows less than about 1.2:1 SWR.

So I decided it was time to start at the top and see if something is 
amiss...and it appears that, so far, not the antennas or feed+divider.   
I am next going to check the TR relay(s)  and will be working agin for 
the ARRL weekend in 2 weeks.   All the leaves are off the trees so that 
may help a little.

Prior I will do some noise floor tests with the 50 ohm LNA terminated 
and see what it looks like.

Again, thanks for all the support.

As an aside, I believe my issues previously noted regarding the big KW 
paging system a mile away on 143.9 has been resolved.  It looks like the 
last of the antennas listed on that site have been migrated to DMRS on 
800MHz.  So I no longer see any of the intermod junk.

Curt
KU8L




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