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[TowerTalk] TH-7 model

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Subject: [TowerTalk] TH-7 model
From: (Pete Smith)
Date: Fri, 21 Mar 1997 12:03:07
At 06:57 PM 3/19/97 -0800, Brian K6STI wrote:
(quoting me)
>>If you want to really be surprised, compare 2-high dipoles with 2-high
>>yagis at the same heights.  We really do spend a lot of effort for a few
>>db.  For example, stacked dipoles at 97 and 69 feet show a gain of 10.3 dBi
>>on 20 meters; the gain of a stack of TH-7s is no more than 15 dBi.

>How did you obtain the values of L and C for the Hy-Gain traps in your
>model? I don't believe even Roger Cox knows them.
>Brian Beezley, K6STI

Hi Brian -- You're right.  The model I used is an idealized
TH-7 with no traps and cylindrical elements.  That's why I said "no more
than" 15 dBi.  I suspect there's something else going on in trapped
antennas (other than losses through trap heating) that costs forward gain.
I'm trying to get a model with measured trap parameters to test this
premise.  A year or so ago someone offered me a TH-6 model, and I'm trying
to remember who it was.  Among other things, I want to see if there is
current "outside" the traps, and maybe some cancellation as a result.


73, Pete Smith N4ZR 

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