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Re: S Band Helix



Hi Robert:

PVC is a dielectric and when placed in close proximity to an antenna, 
will lower the resonant frequency of the antenna, compared to the same 
antenna without any type of raydome or enclosure.  This effect is due to 
the lowered VOP (velocity of propagation) of the PVC.

PVC makes a good Raydome for a 2.4 GHz. antenna, you just need to 
compensate for the lowered resonant frequency of the antenna.

73,

Woody
KJ4SO
AMSAT # 5562


----- Original Message ----- 
From: "Robert V Johnson" <w7lrd@juno.com>
To: <amsat-bb@amsat.org>
Sent: Wednesday, June 15, 2005 10:06 PM
Subject: [amsat-bb] S Band Helix


> Hello
> I'm doing some "stuff" with 2.4 ghz helix'.  I have seen some designs
> that use a plastic type pipe  (pvc) for a form.  I bought a 1.2 ghz
> helix on ebay that is a commercial unit and is enclosed in a large pvc
> type pipe.  Do these forms have a significant impact on the 
> performance
> of these antennas?  I have read conflicting information about this.  I
> want to establish a general consensus of what is "right".
>
> 73 Bob W7LRD
> Seattle
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the 
> author.
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----
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