Rick, please clarify the 37 @-45 degrees info. What is that?
73,
Gerald K5GW
In a message dated 7/18/2010 11:00:39 P.M. Central Daylight Time,
rick.craig@n6nd.com writes:
Scott, you need to shorten the driven element until the impedance is
approximately 25 - j25 ohms (or 37 @-45 degrees) without the beta
match. Then attach the beta match and adjust its length until the
impedance is close to 50 ohm resistive. I have seen some programs
that would give you a good starting length for the beta match based
on the diameter and spacing of the beta rods but I don't have any on
this computer now.
Good luck, Rick, N6ND
NM8R writes:
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,
though.)
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.
Many thanks.
Scott
NM8R
n6nd at n6nd dot com
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