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Re: Cross Boom



Joe,

I have been using a metal crossboom with coax running out it for over 15 
years with good results.  Mount the antennas in an X configuration instead 
of the + configuration to keep the element tips as far as possible from the 
boom.  Don't let the elevation boom stick out past the antenna boom. 
Position the antenna boom so that the driven elements are not a multiple of 
1/2 wavelength from the elevation boom.  See article presented in the 1993 
Proceedings of the AMSAT-NA Symposium, page 56 by Kent Britain, WA5VJB.  He 
made actual measurements, etc.

An added benefit is not having those cables dragging around off the back of 
the antennas, loading up with ice, dragging the roof, etc.  The weight of 
the cables hanging on the back of the antenna booms represents a constantly 
changing torque on the elevation motor as it goes through elevation 
rotation.  The above procedure eliminates all of that so you can balance 
your load on the elevation rotor and have it stay that way.

Also, I have never dropped antennas onto the roof top due to a broken 
elevation boom. :-)

Joe Ennis wrote:
> Lots of feedback on crossed yagis but:
> 
> Wondering if there are any results from using a conductive cross
> boom through say, midway on an 8 foot long 70cm or 23cm helix?
> 
> Bad idea or go for it?
> 
> On Wed, Mar 05, 2003 at 11:53:08PM -0500, Art Goldman wrote:
> 
>>Actually, I just inquired about shipping of those solid 8' masts. It is
>>$40, not because of the weight, but because of the size. They can ship
>>up to 5 masts for the same $40.
>>
>>UPS charges for a 30 pound item, regardless of weight, if the package's
> 
> 
> -- trunc
> 
> tia,
> 


-- 
73, Roy -- W0SL

E-Mail: rdwelch@swbell.net
Home Page: http://home.swbell.net/rdwelch

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