Re: [amsat-bb] Cheap Yagi Antennas for VHF/UHF: experiences?

[K5OE@xxxxxxx]

Fred,

> Send an e-mail to Kent Britian and ask him.  Unfortuately, it is simple if 
> you are the guy who designed the originals, but if I remember correctly, he 
> used YagiMax to design the rough antennas and then used the YagiMax'ed 
> models in NEC to optimise.  I think K5OE said once that the J-matched 
> elements designed to be fed, if they were normal straight elements, with 
> like, 17 ohms impedance.  (3:1 impedance transform ratio with the "J" 
> match).  But don't hold me to that.
> 
> So the simple answer is, unless you already are fairly good at modeling 
> antennas, there isn't a simple answer.

Correct on all points.  My attempts at modeling the J-feed in NEC4 did not work out well, but the YagiMax models do work as advertised (I also do the same thing with folded-dipole designs, using 12.5 Ohms as the feed impedance).
73,
Jerry, K5OE

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