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Re: cross boom?



I went with the choice of a non metallic crossboom because originally I had 
planned to build CP antennas and thought it would be the best option. As it 
turned out, I decided against CP antennas at present because I didn't have 
the measuring equipment to properly determine the velocity factor of the 
coax used in the phasing harneses. I probably will eventually construct CP 
antennas, I even have a second set of aluminum rod elements for the 70 cm 
antenna,but I just decided to simplify things to start with.
73,
Michael, W4HIJ
----- Original Message ----- 
From: "Edward Cole" <kl7uw@acsalaska.net>
To: "Michael A. Tondee" <mat_62@netcommander.com>; <amsat-bb@AMSAT.Org>
Sent: Saturday, April 05, 2008 12:50 AM
Subject: Re: [amsat-bb] Re: cross boom?


> If you are using linearly polarized yagis, just mount each vertical and 
> separate horizontally about 5-6 feet using an aluminum crossboom.  There 
> is no need for non-metallic boom if the crossboom is perpendicular to the 
> plane of polarization.  Ideally, the separation would be so that the field 
> of neither antenna were to touch, but practical separation of the field of 
> the higher frequency antenna is sufficient.  If you get cross-talk between 
> VHF and UHF it may be and advantage to have one antenna place in the 
> opposite polarization.  Then mount each on a 45-degree slant \-----/
>
> I use two x-yagis mounte on metallic crossboom.  The antennas are mounted 
> in an X----X configuration and both are RHCP with no problem of cross-talk 
> using up to 50w.  Preamps are used with both antennas so either mode-UV or 
> VU may be used.  My crossboom is about 6-foot long and both antennas have 
> about 18-foot booms.
>
> 73 Ed - KL7UW
> http://www.kl7uw.com/sat.htm
> for pictures
>
> At 06:38 PM 4/4/2008, Michael A. Tondee wrote:
>>I used schedule 80 PVC with a large wooden dowel pushed inside for added
>>rigidity. I sealed each end with epoxy. It's been going strong for a 
>>couple
>>of years now. I saw your other post about antennas. At present I'm using a
>>four element 2 meter beam and an 11 element 70cm beam in vertical
>>polarization. Both are homebrewed using  Ken Britain's "cheap yagi" 
>>design.
>>73,
>>Michael, W4HIJ

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