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Re: Re: Re: Cross boom length?, (Metal Cross Boom)



William, again this not a personal attack, but the data disagrees.  There 
are several points along the boom where mounting at 45 degrees has no 
measurable impact at all.  It is possible to mount the antenna in the X 
pattern with a minimum of mast protruding through to other side, and not 
impact the pattern.  I agree this is not intuitive, but as you know, lots of 
near field antenna effects are not intuitive.

This is one of those things that everyone 'knows' won't work - but when you 
actually run the experiments you will learn that it can work.

73 my Friend!
Joe
kk0sd

----- Original Message ----- 
From: "William Leijenaar" <pe1rah@yahoo.com>
To: <amsat-bb@amsat.org>
Sent: Monday, March 20, 2006 8:56 AM
Subject: [amsat-bb] Re: Re: Cross boom length?, (Metal Cross Boom)


> Hi Joe and other AMSATs,
>
> You are right for linear polarisation. It can also be
> seen in the measurement results.
>
> For circular it is some different. Even when you use 2
> yagis, each 90 degrees ofset from each other, the RF
> radiation is still in all directions.
>
> Even when mounting the x-yagi in a 45 degree angle to
> the elevation boom, the horizontal angle will be
> reflected by the metal boom, and finally make the
> radiation patern elliptical.
>
> From the measurements you can see that the yagi 90
> degrees to the mast does best. The 45 degrees is half
> worse, and the yagi parallel with the boom is worst
> off all. For both systems, in matter off angle to
> mount the x-yagi on the metal elevation boom, you
> would get the same result.
>
> The idea of mounting the x-yagi on the tip of the
> metal mast might be a solution, but I never tested
> this.
>
> Just my idea,
> 73 de William
> ---
>
>
> Ooo!  One of my favorite topics.
>
> I do not mean to dis-respect William, who is one cool
> dude!
>
> When it is actually measured it turns out metal is
> just fine if you do it
> right.  Metal is cheaper and stronger as well.  Check
> out what happens when
> someone actually measured the results at:
>
> http://www.g6lvb.com/fibermetalboom.htm
>
> Antenna guru Kent Britain, WA5VJB has done the leg
> work for us on this.
>
> 73,
> Joe
> kk0sd
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
> ----
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----
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