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Re: [TowerTalk] Tribander Traps

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Tribander Traps
From: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 12 Sep 2019 14:01:54 -0700
List-post: <mailto:towertalk@contesting.com>

On all bands?

And yes, better F/B doesn't necessarily mean better forward gain.

73,
Dave   AB7E


On 9/12/2019 1:44 PM, K9MA wrote:
I actually measured the pattern of my TH7 and its replacement, a JK Mid-Tri, under exactly the same conditions. The TH7 pattern actually looked a bit better, with better f/b. I can't compare forward gain, of course.

73,
Scott K9MA


On 9/12/2019 15:41, David Gilbert wrote:

You know that power loss doesn't equate to lost pattern gain, right?

Trapped tribanders have shorter elements, which has an effect on pattern, and they have non-optimal element spacing for any particular band, which again affects pattern gain.

I'm not saying that trapped tribanders don't have utility, but compared to a modern non-trapped design they suffer from more than just the heat they generate.

Dave   AB7E


On 9/12/2019 12:55 PM, Glenn Pritchard wrote:
Trapped yagis don't suck up gain, another myth easily dis-proven. I have used trapped yagis and mono banders over the course of 30+ years and at one time had the big Wilson 40M3 I believe it was called, 3 full sized 40 meter
elements on a 40' boom..
It is shown that maybe a trapped yagi has at worst a 0.6 dB loss over a
full sized yagi of the same band. It's no surprise that I like trapped
yagis because of space restrictions right now and having the ability to add
40 meters to one is skookum.

I would like to have mono banders only for 40 and 20 again, perhaps one day.

Glenn, VA7UO


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