You need to measure the impedance at the antenna or though 1/2 wl multiples
of transmission line to get correct readings. With incorrect impedance
values, you will get confusing results when trying to adjust the antenna,
but the SWR value will be correct. BTW, it is pretty easy to design a 2el
yagi with 50 ohm impedance eliminating the need for the match.
Subject: [TowerTalk] Beta match adjustment
From: Scott Yost
Date: Sat, 17 Jul 2010 16:27:14 -0400
Are there any beta match experts onboard who could give me some guidance in
adjusting a beta match on a 40m beam?
I built a 40m 2 element Yagi. Physical detail on the antenna can be shared
if pertinent. It plays well, but I would like to utilize a DXE beta match
to see if I could improve the match.
I have an antenna analyzer thus can measure a variety of antenna parameters.
At my frequency of interest, R=Z @ 26 ohms, and an angle of 0 degrees. This
is without the Beta in place. Beta in place has yielded no worthwhile
results, regardless of setting.
The antenna is on a tilt over/crank down tower so I can access it at ground
level to work, but would like to minimize the number of times my XYL has to
crank the tower up and down. (That was a joke. She actually does help me,
So how does one configure a beta match?
The info that came with the beta match suggests experimenting with the match
and driven element length to tune it at ground level, but the info with it
is vague as to the process. And, I can't uncover a correlation that would
permit me to pre-tune it at ground level that translates to being tuned when
raised on the tower at 65 feet.
I have searched the Tower Talk archives and while I uncovered a lot of good
information, the key to tuning the beta match still eludes me.
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