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WD5DZG

Joined: Sat, Apr 4th 1998, 00:00 Roles: N/A Moderates: N/A

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Triband beam probleem Oct 25th 2011, 00:10 4 1,041 on 25/10/11

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Triband beam probleem WD5DZG on 25/10/11
The question I posed has a typo, it should read 13.97 Mhz not 19 mhz, sorry
Bill WD5DZG
Triband beam probleem WD5DZG on 25/10/11
I am no antenna expert but I have restored an older tribander, sys33 antenna once sold by Maco in Memphis TN. Fortunately I was able to get parts and it is complete and mounted on my Hazer and ready to go up except for one sticky problem.
SWR sucks on 20 meters. It is fine on ten meters, fine on 15 meters with SWR readings near 1:1 and C(x=O) and L(x=0) however on 20 meters the best I can do is one spot about 50kcs wide where I get 2:1 SWR. Capacative reactance is out of sight with Xc =367Pf, Inductance =.315ul The antenna R =40 and X =29 These readings were taken with an MFJ259B.
Orginally I started with an SWR of 1.6 down around 19.97 Mhz which indicated I needed to shorten the 20 meter elements, As I shortened themm the best resonance point has moved up the band into the 20 meter CW portion but I can no longer get a reading below 2:1. I am not sure what to try next, The low inductance reading on 20 makes me suspect that one of the trap coils may be shorted or have some sort of insulation problem. The proceedure I have been using is to make adjustments and crank it up the tower 25 feet or so and run SWR checks (I have a metal roof) Can anyone point me in a likely direction? Bill WD5DZG

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