RE: NEC-LIST:helical ant. modeling

Does anyone have any DATA on the Helix dielectric issue? If you wind the
helix on (for example) a lowloss PVC pipe, how much does it shift the
parameters? I have been told 15%, I don't beleive this for a minute. But
has anybody any real data?

My general feeling is that the travelling wave is travelling inside and
outside the helix, and a dielectric former probably doesn't make more than
5% difference - but this is pure speculation on my part.

..Trevor..

At 09:25 AM 10/4/01 -0400, you wrote:
>Cornel:
>
>You may face a few issues in trying to model the impedance of the helix.
>
>For a thin strip of width, w, the wire radius may be approximated 0.25w
>
>You must also consider the effects of the dielectric substrate on the
>impedance properties of the antenna. If you are trying to model the
>impedance at a specific frequnecy, recognize that the substrate will shift
>the "free space" performance lower in frequency. Any loss in the substrate
>will also impact the impedance properties of the antenna.
>
>Steve Best
>
>-----Original Message-----
>From: nec-list-admin_at_gweep.ca [mailto:nec-list-admin_at_gweep.ca]On Behalf
>Of Cornel Gazdaru
>Sent: Wednesday, October 03, 2001 11:07 PM
>To: nec-list_at_gweep.ca
>Subject: NEC-LIST:helical ant. modeling
>
>
>Hello ,
>
>I try to model a helical antenna, made of a printed line on a flexible
>substrate that then I roll onto a cylinder.
>Does anybody know of an equivalency "printed line width" - "wire
>diameter", so I can accurately obtain some impedance information?
>
>Thank you,
>Cornel Gazdaru
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