[TowerTalk] Antenna matching values
john at carltonhouse.eclipse.co.uk
Tue Apr 22 03:16:32 EDT 2014
The measurements of SWR that you have recorded suggest that something is
quite severely wrong with your array. I'd hazard a guess that one or more
aerials has become disconnected, or that you have water in places it should
not be, either in the gamma match or phasing cables. Your array will not
work at its best.
I presume that with four crossed yagis you are aiming at DX or EME, and my
suggestion is not to patch over the problem with a matching device, but to
get the aerials sorted out.
I hope you know that for an array of four yagis, when you set up the gamma
match you must do each one individually ? Then add the phasing harness or
power splitter. Arrange the aerial to be pointing skywards when setting up
the match, with the reflector a meter or two off the ground. Remove any
clutter from the test area (other cables, metal ladders, your body(!) etc).
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Drax
Sent: 22 April 2014 04:44
To: towertalk at contesting.com
Subject: [TowerTalk] Antenna matching values
I have a phased set of four 2 meter Yagi's that I tuned using the gamma
matches on the antennas the best I could.
Now that the antennas are 90 feet in the air I have a slight SWR problem at
the input of the array and cannot load my 1kW solid state amp to full power
without it locking out.
I'd like to put a matching circuit at the input of the array on the tower
end to avoid feed line losses.
I need to know what fixed values of impedance, capacitance, and inductance
to put into two T match or other circuits to get nearer to a 1:1 SWR.
This is what my antenna analyzer says now:
When using horizontal polarization
144.100 MHz R=17 X=0 SWR 2.9
When using vertical polarization
144.100 MHz R=36 X=25 SWR 2.0
I know one of you is a good electrical engineer and can point me in the
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