Topband: Gamma match success

[Edward Sawyer]

I usually use the complex impedance as my guide here.  What is the resistive
component vs the model?  If the SWR is flat it is often because the
resistive ( R ) portion is too high and dominating the frequency dependence
of the X portion.  Adding radials can improve that as well as the loss of
the match itself.

 

A model of the ideal complex impedance vs ideal ground and lossless match
components compared to what you are actually reading will help point you in
the right direction.

 

My 70 ft T top Verticals with 45 1 / 4 wave radials, have a resistive
component that matches with the model if I make the ground less than average
- which is in fact the case here in Central Vermont.  Modeling suggests that
adding another 20 radials is not going to add much to that equation so I
stopped there.  I use choke baluns at the feed (bottom) to minimize any coax
radiation and adjusted the SWR based on the length of the wires only
(keeping the T portion symmetric).  The individual Ts have about a 60khz 2:1
bandwidth vs an ideal of about 35 khz.  But its all modelable ground losses.

 

I phase 2 of them for end fire to EU and some other interesting patterns
depending on phase relationship.  The phasing clearly affects the SWR.

 

Ed  N1UR