6 Element UHF Yagi ~450-460MHz

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fredg

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I am thinking of giving it a go and building this Yagi:

http://www.mncarg.org/projects/uhf6el.jpg

It is designed for 430-440MHz.

Question: If I am using this just for Scanning is it critial that I tune it for the freq I am shooting for?

To answer my own question.. I currently use a Larsen 2/70 antenna that works fine so I would assume this Yagi would pull in 450-460 just fine even though it is cut for 430-440. I just wonder if I would notice the difference.

Question: Anybody know how I would scale this for 450-460? If I shorten the Driven Elelment do I need to shorten the Directors and Reflector? What about the spacing?

Thanks!
 

W4KRR

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For scanning purposes, the yagi in question would probably work fine; you probably wouldn't notice any difference by using a yagi designed for 450-470MHz. And yes, if you were to adjust the dimensions of the yagi to work at the higher frequency range, you would have to adjust the length of all the elements as well as the spacing between them. I don't know the exact amount of adjustment you would need, but it wouldn't be much.
 

fredg

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Thanks Ken, I have a couple of Yagi design programs and they all come up with different dimensions when I design one. Even when looking at commercial offerings, you can tell they are using some dimensions totaly different than what my software is spitting out.

From what I read the actual algorithm for designing a Yagi is not really straight foward and requires experimentation to tweak it just right...

Anyway... I think the design I linked to looks like it may have some promise so I may give it a shot...
 

k9rzz

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The pattern might be skewed because at 460, the 430 directors may act like _reflectors_.

It might work right ... it might not.
 
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