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

To: donhall161 <>
Subject: Re: [TowerTalk] 50 ohm yagis (40M2L) ?
From: Kevin Normoyle <>
Date: Sun, 18 Jul 2010 12:23:47 -0700
List-post: <">>
Don K5AQ to me mentioned the 50 ohm yagis in the ARRL antenna book. . I 
have 20th ed so. let's see.

oh yeah Don's right..I guess I misremembered stuff..

But let's look at the performance:

using the ARRL/N6BV Yagi for Windows, the 2 element 19.5 ft boom 
(240-20W.YW) has 2.0 SWR from just 7.025Mhz to 7.2Mhz. (at 60')

Maybe when I was playing with simulations, I was thinking "50 ohm swr < 
2:1 for the full 7-7.3Mhz...with good gain and reasonable f/b --> not 
possible). So while I said one thing in my prior post, I guess I was 
thinking in the context of wanting <2:1 50 ohm swr over the full 7-7.3Mhz.
(which is one of the advantages of a moxon-like design)

Yes the 50 ohm goal is met in the ARRL design (20 ft boom, full length 
elements) ... but not over the full band, right. Tweaking it to a lower 
impedance, and matching it, can give better swr bandwidth?

I think my bent tip yagi shows that?. It's full length elements, bent, 
with a hairpin (coil).

Maybe that was my point..tweaking a 40M 2L to 50 ohms, makes you give up 
stuff....i.e. it's a peaky 50ohms.



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