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Re: [TowerTalk] 50 ohm yagis (40M2L) ?

To: "'Kevin Normoyle'" <knormoyle@surfnetusa.com>, <TOWERTALK@contesting.com>
Subject: Re: [TowerTalk] 50 ohm yagis (40M2L) ?
From: "Tim Duffy K3LR" <k3lr@k3lr.com>
Reply-to: k3lr@k3lr.com
Date: Sun, 18 Jul 2010 11:50:37 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hi Kevin,

The W6NL Moxon is pretty simple (no matching components) and it is a 50 ohm
feed.

Check out:

http://www.k3lr.com/engineering/moxon/W6NL_Moxon104.pdf

The VSWR never gets over 1.4:1 from 7 to 7.3 MHz

73,
Tim K3LR


-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Kevin Normoyle
Sent: Sunday, July 18, 2010 11:44 AM
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] 50 ohm yagis (40M2L) ?

On 7/18/2010 8:18 AM, john@kk9a.com wrote:
>    BTW, it is pretty easy to design a 2el
> yagi with 50 ohm impedance eliminating the need for the match.
>
> John KK9A
>    

40M 2L 50 ohm impedance? with reasonable gain/f/b/swr bandwidth? I don't 
think so, or I couldn't do it
(with my boom length and full length elements)
Am I missing something?

Actually I did create one by accident. If you off-center feed the DE, 
you can get a 50 ohm match without too much loss in the other metrics.
I thought that was interesting. I saw someone proposed that elsewhere, 
and it actually does work. It would be possible mechanically, but there 
is a loss in gain.

Does anyone have a 40M 2L with 50 ohm input, with no matching 
components? Well I guess a moxon does it, and maybe some dual-driven 
things? what am I missing? I thought a simple 40M2L can't, as far as I 
tried.

-kevin
ad6z
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