Since Scott mentioned that he measured " R=Z @ 26 ohms, and an angle
of 0 degrees", I assumed his antenna analyzer gives him a reading as
a vector. So I converted 25 -j25 to a vector. It certainly is
easier to not use a vector and keep the real and imaginary parts separate.
73 Rick, N6ND
At 04:27 AM 7/19/2010, TexasRF@aol.com wrote:
>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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>
>
>
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