[TowerTalk] 2-el 15/20 meter duobander

[Jeff]

For a basic yagi, multiband or otherwise, NEC2 works fine.  Where NEC4 
provides an advantage is with unusual geometries and features in the ground.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Tom Hellem
Sent: Friday, December 01, 2017 6:45 PM
To: Jim Thomson
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] 2-el 15/20 meter duobander

Jim-
I am curious about why you are suggesting that one needs NEC 4 software to 
design a 2 el. duobander.

FWIW I basically took a C-3 and removed the 10M elements, tweaked it with a 
model in EZnec (NEC 2), built it according to the model. It ended up being 
resonant exactly where the model predicted with an swr of 1.0 at resonance 
on 20. However on 15 it ended up with 2.0-1 swr .  Maybe I should have used 
NEC4.

Tom H
KOSN

> On Nov 29, 2017, at 6:04 AM, Jim Thomson <jim.thom at telus.net> wrote:
>
> Date: Tue, 28 Nov 2017 16:38:40 -0700
> From: W0MU Mike Fatchett <w0mu at w0mu.com>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] 2-el 15/20 meter duobander
>
> <Why not take the measurements from a C3?? I think it is just 2 ele on 20
> <and 15 with 4 on 10.
>
> ##  wont work.   Different yagi, and even if it did sorta work, he would 
> have to use the
> identical tubing schedule.   Whats  required is  auto ez, NEC-4  and yagi 
> mechanical to
> design the eles.
>
> Jim   VE7RF
>
>
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