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Re: [Antennaware] Space between antennas

Subject: Re: [Antennaware] Space between antennas
Date: Fri, 20 Jul 2007 20:44:29 +0000
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Does anyone know if there will be any interaction if the 40-2CD is rotated 90 
degs to the tribander?  

Jim, KR9U

De: K9AY [] 
Enviado el: Viernes, 20 de Julio de 2007 01:06 p.m. 
Para: Jorge Diez - CX6VM; 
Asunto: Re: [Antennaware] Space between antennas 

I have also recently heard stories of big interaction problems with the 
XM240, worse than the older 40-2CD. The only other commercial antenna I 
about is the old KLM 2- and 3-element 40M beams, which have a small 
on 15M, but are quite usable. 

Perhaps someone can develop a modification for the Cushcraft beam. 

It is not difficult to design a "shorty forty" for low 15M interaction. 
distance from boom to loading coils is a key parameter. My homebrew 
element 40M beam has loading coils about 6 foot out from the boom (outer 

elements are #14 wire inside 20-ft. fiberglass fishing poles). 
are near 26 and 48 MHz. I detect no changes on my X9's performance with 
without the 40M beam. I might note that these resonances changed very 
when the driven element was used alone as a rotatable dipole, and after 
refelector was added. 

73, Gary 

> Unfortunately, the Cushcraft 40 will detune the TH7DXX on 15m at any 
> spacing you can manage on the same mast. 
> There have been numerous instances locally of "pulling" any 15 meter 
> antenna's tuning by co-masted Cushcraft 40's. It also modifies the 
> pattern at 15m. 
> This happens because without modification a 40 antenna is also 
> resonant at three times the frequency. Some 40m beams are 
> specifically designed to be placed in proximity to tribanders, etc. 
> The Force 12 x40N antennas are linearly loaded, and their secondary 
> resonance is around 18 MHz instead of 21. Also their Delta x40 
> antennas were specifically designed to eliminate secondary 
> resonance in 21 MHz band. 
> There may be other commercial 40m antennas that are non-resonant at 21 

> MHz, but I don't know of any. 
> 73, Guy. 
> | Hello, 
> | 
> | I will put a Hy-Gain TH7DXX and a Cushcraft 2 elem. 40 mts Yagi in 
> | the same mast on top of a tower. 
> | 
> | Will apreciate any recomendation about will antenna must be at top 
> | and the space between both antennas for not interaction. 
> | 
> | Thanks in advance 
> | 
> | 73, 
> | Jorge 
> | CX6VM 
> | 

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