I was describing the curvature of the antenna. A curtain antenna is never a
closed loop, or in this case a cylinder. But it can have a
specific curvature so there will be a focus!
I wrote "cylindrical" - please observe the quotes- as opposed to "spherical"
or "parabolic" surfaces. Please remember your spherical trigonometry :)
In my case the curtain has a horizontal cylindrical angle of about 10 to 20
degrees due to the limitations imposed by the trees which are used as
infrastructure for it.
Preliminary computations show a 70dB B/F ratio - for the composite system -
with a quite a wide horizontal dispersment. Forward gain is only improved by
2.7dB. I kind's hopped to get some more. I think the curtain is to long
horizontally for the 20m band. I'll try to make it exactly one lambda for a
Thank you for your reply.
> -----Original Message-----
> From: email@example.com
> [mailto:firstname.lastname@example.org]On Behalf Of Don Havlicek
> Sent: Wednesday, June 12, 2002 9:07 AM
> To: Alex
> Cc: email@example.com
> Subject: Re: [Antennaware] Modeling a composite antenna
> A cylinder has NO focus, a parabola/paraboloid does.
> If you construct what you have suggested, only the RF entering the
> 'reflector' along the line of the boom of the TH7 will be reflected back
> to the AXIS of the cylinder .. and that is where you must place the
> DRIVEN ELEMENT of the TH7.
> A better arrangement might be to add additional reflectors to the TH7,
> but that would be a mechanical nightmare, as they would be trapped and
> placed at a distance equal to the DE/Ref distance of the TH7.
> Alex wrote:
> > I am planning to erect a 60m long by 30m tall "cylindrical"
> curtain and in
> > it's foci a TH7.
> > What software can model this combination and where can I get it .
> > TIA, Alex
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