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Re: [TowerTalk] Antenna choices

To: "tower" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Antenna choices
From: "StellarCAT" <rxdesign@ssvecnet.com>
Date: Tue, 7 Apr 2015 19:57:02 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
> ...actually I find that M2 is right on in their numbers ? no specmanship here 
> whatsoever. 

How did you determine that? Inquiring minds want to know. Cheers,Steve K7LXC


I used their manuals and created models for the 20M4DX, the 20M5LGS, the 20M5, 
the 15M6DX and the 10M7DX. All of the results – with essentially no changes 
other than a quite small change to the driven element length to get it about in 
the center of the band, were right on. This is just some of the results:

Comparing the 20M4DX to the 20M5LGS 

1 x 4 el  @ 133’        14.0Mhz = 14.8dbi/17.8db FB      14.2Mhz = 
15.0dbi/23.8db FB  (free space:  9.1/9.4 dbi respectively)
2 x 4 el  @ 133’/77’ 14.0Mhz = 17.0dbi/15.4db FB       14.2Mhz = 17.3dbi/20.4 
FB  

1 x 5 el  @ 133’        14.0Mhz = 16.0dbi/23db FB      14.2Mhz = 16.4dbi/23.7db 
FB  (free space:  10.3/10.7 dbi respectively)
2 x 5 el  @ 133’/73’ 14.0Mhz =  17.9dbi/19.0db FB    14.2Mhz = 18.3dbi/28.6 FB  

so with the 5 elements there’s ~1 db more gain and 5db more FB at the bottom 
and over 8 db at 14.2. 

the 5 element doesn’t get as much benefit from stacking as the 4 el, 
respectively 1.9db vs. 2.25. Wider spacing on the 5’s didn’t help any more than 
0.15 db before it started to fall off again. 

Note for the LGS 10.7 dbi is what they say and is what I got – and they say 23 
db FB – I got 23.7! Same with the rest, very good correlation to what they 
publish. As for the comment about their log – indeed I wasn’t speaking 
specifically about their log – more about their monobanders – but even the 
number you show seems reasonable to me. 

Gary
K9RX
[Hey Dave, ‘7E]


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