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[TowerTalk] Trap vs. Full Size - Not much difference?

Subject: [TowerTalk] Trap vs. Full Size - Not much difference?
From: "Mark Adams, PE" <>
Date: Wed, 20 Dec 2006 14:38:09 -0500
List-post: <>
Hi Gang,

As I continue self torture with the decision between a Force 12 C-4 and 
Hy-Gain Explorer 14 with 40M kit, one significant question still nags to 
be addressed.

The C-4 is a 2 el on 20-10 with optimum spacing for each band and full 
size elements. The Exp14 has fixed spacing but has 3 elements per band. 
On 40M, the C-4 is linear loading and the Exp14 appears to be a 
combination of linear and capacitive. So if one compares FWD gain and 
F/B for each band for each antenna, it is clear that the Hy-Gain wins on 
10M and is real close to the C-4 on 15 and 20. I've made this "guess" 
based on:

where Cebik has modeled a full size 2 element 15 and 20M beam vs a 
trapped 2 element 15 and 20M beam. He finds the trapped beam to be equal 
in performance on 15M and down 0.5 dB in Fwd gain. But my comparison is 
with a full sized interlaced 2 el to a trapped 3-el.

Neither antenna has much edge in durability for my location in WNY. 
During the 24" wet snow event this October, friends lost a bunch of 
TH5's, T10's, C19's. The only HF antennas that came out unscathed (to my 
knowledge) were my 3el 10M NBS HB and a my neighbors TH3. Actually, the 
TH3 did have 2 elements rotate about the boom a bit, but that's it.

OK, comments? FWIW, this antenna will be largely for contesting at QRP 
levels. I really cannot go bigger because I want to keep my 6 and 2M 
beams on the same mast. So the 8.5 square feet of the Exp14 is the limit.

Mark K2QO
(my celeb status is confirmed by the photo on page 97 of the 12/06 QST :-))


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