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



Bill,

I shared your opinion for many, many years and vigorously defended it. After 
reviewing the research presented here:

http://www.g6lvb.com/fibermetalboom.htm

and discussing actual implementations of this research with Roy Welch, W0SL, 
I decided to try it myself. I have used nothing but fibreglas booms my 
entire amsat career. I changed out the fibreglas boom for a metal boom, and 
set up my 435 Mhz right-hand circular antenna exactly as shown by the link 
above. I do mean EXACTLY!

I could detect no change in gain, no change in circularity, and no azimuth 
skewing of the pattern when using the metal cross boom as described above.

In summary, I have changed my mind. The data presented by the above link, my 
discussions with knowledgable hamsat operators like Roy Welch, and my own 
experience show that a metal cross boom can be used at 70 cm with no 
discernable problems in gain, pattern or circularity. I don't use insulated 
booms any more.

73,

...hasan, N0AN

----- 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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