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Re: [TowerTalk] New Tower up With Some Issues 2L40 TH7

Subject: Re: [TowerTalk] New Tower up With Some Issues 2L40 TH7
From: David O Hachadorian <>
Date: Sun, 15 Feb 2004 07:15:11 -0700
List-post: <>

On Sat, 14 Feb 2004 17:27:13 -0800 "Jim W7RY" <>

> Now the TH7 just went up 9' below the 40. Re-checked the match on 
> the 40 and it was not resonant at 7.090. Looks as if the 2 element 
> is effected little by the tribander.
> Now checked the match on the TH7, I was not so good.
> The TH7 is using the "DX" element lengths.   
> 20 Meters: flat at 14.090. Climbs to 1.3:1 at 14.000 and up to 2:1 
> at 14.250.
> 15 Meters: 1.2:1 at   21.390  Never lower than that.
> 10 Meters: 1.2:1 at 28.600.  above 2.5:1 at 21.100.

Someone advised checking with a real swr meter, rather
than an antenna analyzer. - Good advice.

Also, you may have chosen an unfortunate length of
feedline for the 40m antenna. It may be making the
driven element resonant near one or more of the
higher bands. Try shorting and unshorting the 40m
feedline, while observing swr on 10, 15, and 20, to
see if the swr changes. If the swr changes significantly
while doing this test, you can add a short piece of
feedline to the 40 to lessen or eliminate the

The Cushcraft 2 el 40, especially the older one,
with ungrounded reflector, usually doesn't affect
tribanders too badly. The loading coils cause it
not to have a 3rd harmonic resonance on 15. It
works fb on 17m though.

Dave Hachadorian, K6LL
Yuma, AZ


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