Thanks to all for the feedback.
Really not good news for me, I have just one tower!,...
73,
Jorge
CX6VM
-----Mensaje original-----
De: K9AY [mailto:k9ay@k9ay.com]
Enviado el: Viernes, 20 de Julio de 2007 01:06 p.m.
Para: Jorge Diez - CX6VM; antennaware@contesting.com
Asunto: Re: [Antennaware] Space between antennas
I have also recently heard stories of big interaction problems with the
new
XM240, worse than the older 40-2CD. The only other commercial antenna I
know
about is the old KLM 2- and 3-element 40M beams, which have a small
effect
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.
The
distance from boom to loading coils is a key parameter. My homebrew
52-foot
element 40M beam has loading coils about 6 foot out from the boom (outer
elements are #14 wire inside 20-ft. fiberglass fishing poles).
Resonances
are near 26 and 48 MHz. I detect no changes on my X9's performance with
or
without the 40M beam. I might note that these resonances changed very
little
when the driven element was used alone as a rotatable dipole, and after
the
refelector was added.
73, Gary
K9AY
> 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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