We tried that around here and the interaction was worse. At right angles the
boom is in play with
the reflector acting as end-loading.
In addition to the Force 12 models, the Optibeam 2-40 and 4-40 are specifically
engineered for
proximity to tribanders.
If one puts up the 402cd, then just get used to using a tuner on 15 meters. The
fellas here wanted a
nice low SWR on everything, but the antennas worked. To what extent PERFORMANCE
(not swr) was
affected was very difficult to gauge.
-73 Guy.
----- Original Message -----
From: <jbwolf@comcast.net>
To: <antennaware@contesting.com>
Sent: Friday, July 20, 2007 4:44 PM
Subject: Re: [Antennaware] Space between antennas
| Does anyone know if there will be any interaction if the 40-2CD is rotated 90
degs to the
tribander?
|
| Jim, KR9U
| __________________________
|
| 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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