Re: Mathematically challenged

Posted by N5GE on Nov 16, 2007; 9:21pm
URL: http://elecraft.85.s1.nabble.com/Mathematically-challenged-tp366490p366496.html

On Fri, 16 Nov 2007 11:50:44 -0800, you wrote:

>I want to try and build an HF two Element Vertical Antenna for 20 meters.
>
>While there are several java scripted web-sites that will calculate and provide the physical measurements for the Driven, Reflector elements and spacing.  
>
>I would like to use my MJF-259 to complete the fine tuning during construction and given that the frequency of the Driven element will not be the resonant frequency of the reflector.  
>
>What would a good equation be to determine the resonant frequency for the reflector based on the desired frequency for the Driven element?
>
>Some references that I have found state the Reflector is approximately 4% longer than the Driven and the Director is 4% shorter, with element spacing 0.15 to 0.25 of the desired freq.  I would like something a little more specific.  Not that I can build it to spec or that the MFJ259 will be that accurate, I would still like to work with figures that provide something other than approximate.
>
>73 K2CG
>Chuck G.
>

[snip]

Back when I was a Novice I built a 15m 2 element Yagi using the information for
Yagi's in the ARRL antenna book.  I chose to build a driven/reflector style
beginning with a reflector length of (468/f in mc) X 1.05 and DE length of 468/f
in mc.  It worked very well.

 
Tom, N5GE

http://www.n5ge.com
http://www.eQSL.cc/Member.cfm?N5GE

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