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Re: Circularly-polarized antennas for two-way?

 

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ive actually built and tested cp antennas for fm broadcast with great results when stacked. i completely agree why no one will build a 2 meter or 440 version. that being said....im either going to re-visit this and try to calculate the dimensions...unless someone super smarter than me can whip one up in a program and give me the dimensions and ill build it. ill post pics of the fm broadcast prototype i built(copied) later.

jonny? kf6phx

From: [email protected] <[email protected]> on behalf of neal Newman via groups.io <cozy659@...>
Sent: Sunday, November 20, 2022 4:10 PM
To: [email protected] <[email protected]>
Subject: Re: [repeater-builder] Circularly-polarized antennas for two-way?
?
?As a Broadcaster, I have asked many of the Commercial? Antenna? manufacturers? If? their Engineers? could develop a prototype antenna for me.? ZERO takers.
?? what I am looking for is a Vertically mounted? Horizontally Polarized? antenna? with at least 9-19 db gain? around 426-440 Mhz? spectrum? for an ATV? repeater
? Yeas? ago? I built a loop ring open Alford slot cage antenna. It worked ok.? Lost the design plans? in a house fire.?? have not been able to Find them since.?? But? looking for a Pipe style? Slotted Dipole array.
? Anyone? have? any? Knowledge? on designing these with specs?? for 426-440??

? Neal? KA2CAF
?not sure if there is still an ATV? repeater ? located at Brookdale? Community College? in NJ? on the WBJB? FM? Tower.
?still have My ATV? gear? , and want to Tinker.



On Sunday, November 20, 2022 at 06:33:13 PM EST, Chris Boone <setxtelecom@...> wrote:


Circular polarization eliminates a lot of mobile flutter due to reflections. Radio broadcast industry normally uses right hand circular polarization on FM and left hand circular polarization on the HD signals. Television is now leaning more toward elliptical with 70% in the horizontal and 30% in the vertical.
If I recall the test that was mentioned in the earlier email was written up in Bill Pasternak's "All you wanted to know about FM and repeaters" book. The CP array that was built used two Cushcraft four poles mounted at 45¡ã off of vertical in each direction. Basically a 4 bay turnstile turned on its side.

I thought about building a CP for 6m. The Nicom series in FM broadcast is real easy to duplicate and works rather well. On 2 meters it would be even easier since the size would be smaller.

Chris WB5ITT?


On Sun, Nov 20, 2022, 5:13 PM John Huggins <john.huggins.ee@...> wrote:
I've gone down this rabbit hole as well.? There's some ancient documentation out there showcasing some experiment?where a linear and circular antenna at a repeater site were choosable by the users (via DTMF) I guess to get a consensus?which one offered?what the users' observed?as "mo better."? Apparently?the CP won the election.

It's said even with vertical mobile antennas, the randomness of reflections of things can cause fluttering and such and CP on the mountain top alleges to help with this.

All this in mind, I'm actually in a position to test exactly this here in Virginia in the upcoming year... so I am.? Stay tuned.

73
John, kx4o?

On Sun, Nov 20, 2022 at 5:48 PM Matt Wagner <mwaggy@...> wrote:
Howdy,

I went down a little bit of a rabbit hole reading about the use of circular polarity in antennas. I'm curious if anyone's experimented with it for repeaters or traditional two-way stuff.
But, while I can read lots of theory about circular polarity in antennas, and see people using it for various purposes, I've found absolutely nothing about people running it on traditional two-way systems. Is this something people have played around with? It sounds like it could be useful, but I can't possibly be the first to have thought of this, so I wonder if it ends up not working out well?
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