[TowerTalk] Antenna matching values

Jim Brown jim at audiosystemsgroup.com
Tue Apr 22 02:35:34 EDT 2014

Hi Drax,

Some thoughts. Those SWR values at the TX end of a feedline indicate a 
significantly higher SWR at the antenna, which in turn suggests that 
something is wrong up there. Or perhaps somewhere along the line 
something is wrong. The "somethings" could be anything from a badly 
installed connector to a bad piece of coax to a junk connector at a 
splice. On in the polarization switching.

First step -- get one of those EE types with an antenna analyzer that 
can do a Time Delay Reflectometry (TDR) measurement of the line and look 
for problems. That TDR will tell you if there is a cable or connector 
problem, and it will tell you, with several inches, where it is (he'll 
also have to measure the Vf of the line to get that info.

Second, have that EE type make swept impedance measurements, plug them 
into SimSmith, and in Sim Smith, translate the measurement made in the 
shack to the antenna.

Poking around with the analyzer for a while may give some good clues 
about where to look. Sim Smith can help someone who knows how to use it 
design a matching network. But I'd try to find and fix the problem 
before I tried to put lipstick on a pig.

73, Jim K9YC

On 4/21/2014 8:44 PM, Drax Felton wrote:
> 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

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