|
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.
Of particular interest to me is using it only on one end. A lot of satellite comms use circular polarity on both ends, and can get fairly good isolation between right-handed and left-handed circular polarity. But, as I understand it, a lot of broadcast FM uses circularly polarized antennas to listeners with linearly polarized antennas, because there's a blend of vertical and horizontal antennas out there, not to mention the 45-degree pattern seen on some cars now.
From what I've read, about 3 dB is lost when a circularly polarized signal is received by a linear antenna. But what's gained is that the antenna orientation doesn't matter, and you avoid potentially 20-30 dB loss to an antenna in the wrong orientation. (Broadcasters can work around this by stacking a number of FM bays like we do with folded dipole arrays.)
I also read a tiny bit about some experiments on HF, on the theory that multipath fading would be reduced significantly.
It would seem to me that doing something similar on a repeater antenna could be beneficial, especially if you're serving users on portables. The signal strength for a ham repeater I'm listening to in the background is bouncing around by more than 10 dB right now; I suspect part of it is the fiberglass whip on top of a hill flexing a bit with the 30mph wind gusts we're having. I've also found that with somewhat weak signals being heard on an HT, sometimes the signal is greatly improved by tilting the radio in some particular direction, maybe due to various reflections and obstructions along the way.
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?
73, Matt, N1ZYY
|
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?
|
If you are considering CP for a repeater station I would suggest diversity reception using as a second antenna a horizontal loop. Use two identical receivers and a voting comparitor.?
--
The Real RFI-EMI-GUY
|
I believe there was some research using both horizontal and
vertical polarity with pagers back in pager days.
I think it was Bogner that made the antennas for 900 Mhz. Pagers
are seldom vertical or horizontal. The test were in deep urban
areas. What I remember about the results was about a 3dB
improvement in receiving pages.
They decided that down tilt was more effective for a lower cost.
On 11/20/2022 5:12 PM, John Huggins
wrote:
toggle quoted message
Show quoted text
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?
|
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?
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?
|
?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?
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?
|
?
I've always wanted to get a circular polarized
antenna to try satellite work.? Long ago back in the 70s, a friend who
built a two meter repeater and I did a lot of experimenting? I was his weak
signal generater when needed.?I was about 55 miles away.? We?also
did a bit of playing horizontal versis vertical polarization.? We didn't
have circular stuff.? First thing we found was that two meters could go
into some very deep fades, lasting 4 or 5 minutes.? We found that vertical
polarity was often a bit stronger on peaks, but the horizontal antennas were
more consistent, not quite as strong, but didn't fade out quite
so?much.?
?
----- Original Message -----
Sent: Sunday, November 20, 2022 5:10 PM
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?
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?
|
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
toggle quoted message
Show quoted text
?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?
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?
|
Neil you're not the only one! I've tried getting some information from the manufacturers on CPs and got almost nothing. I do know however that a North Texas group took a DB420 and rotated the dipole elements 90¡ã to horizontal with each pair out of phase at 180¡ã. This meant one dipole on the left was rotated 90¡ã over while the other dipole on the other side was rotated 90¡ã toward the viewer.? All bays were done this way...A pattern check showed an almost perfect horizontal pattern. DB would not acknowledge it because it was modification of their design and they had no intent on trying to prove it one way or the other. If you need more info you could email me direct
Chris WB5ITT?
?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?
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?
|
I made a CP (helix) antenna for analog 800MHz cellular.? This was in the early 1990s, when the part 22 cell rules required TX to be vertically polarized so I didn't mess with the TX antenna. I did this in an urban environment.? I had an automated measurement setup make 10 receive signal strength measurements per second on the vertical and also on the CP antenna when that channel was active.? The peak signal strengths were similar, but the average signal strength was higher on the CP antenna. Measuring receive signal strength on two vertical antennas 10 feet apart, and doing diversity "combining", was a couple of dB better than one CP antenna. I suppose I should have tried two helix RX antennas, but rhe company picked up two more markets and I got too busy to continue with the experiments. Eric
WB6TIX
|
I heard, quite a few decades ago, that some who worked at Jampro (broadcast Fm antenna manufacturer) in California, had a scaled back model of one of the FM CP antennas for CP, on 220 MHz. I've always thought about someplace like NYC should try a CP antenna due to the concrete canyons and multipath. Anyone else hear about the Jampro on 220?
Tom K8TB
|
I like RFI-EMI-GUY's recommendation of setting up a pair of receivers fed into a voter -- although building a CP antenna and setting up a receive voter is _two_ projects in one...
From what I've seen, Comprod makes a circularly polarized antenna, the 205-70, but doesn't really hype it any:
by VE3BYT and VE3KL describes the Skew-Planer antenna, which looks a lot like the cloverleaf antenna seen in 5.8 GHz drones and such. They note difficulty stacking them with anything metallic; it's unclear if this is a unique challenge with this design, though.
I think being able to stack a few of them in an array would be helpful, especially since a singular one effectively has -3 dB gain. Could be a fun little antenna project.
Neil you're not the only one! I've tried getting some information from the manufacturers on CPs and got almost nothing. I do know however that a North Texas group took a DB420 and rotated the dipole elements 90¡ã to horizontal with each pair out of phase at 180¡ã. This meant one dipole on the left was rotated 90¡ã over while the other dipole on the other side was rotated 90¡ã toward the viewer.? All bays were done this way...A pattern check showed an almost perfect horizontal pattern. DB would not acknowledge it because it was modification of their design and they had no intent on trying to prove it one way or the other. If you need more info you could email me direct
Chris WB5ITT?
?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?
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?
|
Comprod looks interesting but can it be stacked in bays? Plus the cost is likely high for the average ham... I would think you could get a tubing bender and make your own for a heck of a lot less.
Many years ago when I was involved with an ATV repeater in Beaumont Texas we built a CP antenna similar to a Skew Planer ... In fact we supplied one to the Johnson Space Center amateur radio club for an ATV experiment off the shuttle in the mid-80s.. KE5O and I are the only two non NASA employees to be members of W5RRR because of that... Didn't hurt that another amateur friend of ours, Jerry Coles and I can't remember Jerry's call off the top of my head right now, was an engineer at NASA and flew a modified IFR 7550 on board the shuttle at our suggestion.. Jerry later worked for IFR and was instrumental in getting the 1600 working when the production line couldn't..
Ahh the fun days ?
I actually kicked around the idea about building a bat wing for 420 ATV.. or a traveling helix which I saw at KTVT 11 in Dallas in 96...it's described in Vol II or III of the Antenna Handbook by Yo and Lee.. The one at Channel 11 DFW was actually hand built by local consultant engineer William JB Smith..
CWB
On Sun, Nov 20, 2022, 8:39 PM Matt Wagner < mwaggy@...> wrote: I like RFI-EMI-GUY's recommendation of setting up a pair of receivers fed into a voter -- although building a CP antenna and setting up a receive voter is _two_ projects in one...
From what I've seen, Comprod makes a circularly polarized antenna, the 205-70, but doesn't really hype it any:
by VE3BYT and VE3KL describes the Skew-Planer antenna, which looks a lot like the cloverleaf antenna seen in 5.8 GHz drones and such. They note difficulty stacking them with anything metallic; it's unclear if this is a unique challenge with this design, though.
I think being able to stack a few of them in an array would be helpful, especially since a singular one effectively has -3 dB gain. Could be a fun little antenna project.
Neil you're not the only one! I've tried getting some information from the manufacturers on CPs and got almost nothing. I do know however that a North Texas group took a DB420 and rotated the dipole elements 90¡ã to horizontal with each pair out of phase at 180¡ã. This meant one dipole on the left was rotated 90¡ã over while the other dipole on the other side was rotated 90¡ã toward the viewer.? All bays were done this way...A pattern check showed an almost perfect horizontal pattern. DB would not acknowledge it because it was modification of their design and they had no intent on trying to prove it one way or the other. If you need more info you could email me direct
Chris WB5ITT?
?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?
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?
|
Actually, My suggestion is for the second antenna to he a horizontal loop avoiding the hassle and loss related to a CP antenna.
toggle quoted message
Show quoted text
On Sun, Nov 20, 2022 at 09:39 PM, Matt Wagner wrote:
I like RFI-EMI-GUY's recommendation of setting up a pair of receivers fed into a voter -- although building a CP antenna and setting up a receive voter is _two_ projects in one...
?
From what I've seen, Comprod makes a circularly polarized antenna, the 205-70, but doesn't really hype it any:
?
by VE3BYT and VE3KL describes the Skew-Planer antenna, which looks a lot like the cloverleaf antenna seen in 5.8 GHz drones and such. They note difficulty stacking them with anything metallic; it's unclear if this is a unique challenge with this design, though.
?
I think being able to stack a few of them in an array would be helpful, especially since a singular one effectively has -3 dB gain. Could be a fun little antenna project.
Neil you're not the only one! I've tried getting some information from the manufacturers on CPs and got almost nothing.
I do know however that a North Texas group took a DB420 and rotated the dipole elements 90¡ã to horizontal with each pair out of phase at 180¡ã. This meant one dipole on the left was rotated 90¡ã over while the other dipole on the other side was rotated 90¡ã toward the viewer.? All bays were done this way...A pattern check showed an almost perfect horizontal pattern. DB would not acknowledge it because it was modification of their design and they had no intent on trying to prove it one way or the other. If you need more info you could email me direct
?
Chris WB5ITT?
?
?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?
?
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?
?
?
?
?
?
? -- The Real RFI-EMI-GUY
|
Will a voter switch fast/often enough to keep up with the flutter style fading?
Eric WB6TIX
On Mon, Nov 21, 2022, 09:00 RFI-EMI-GUY < rhyolite@...> wrote: Actually, My suggestion is for the second antenna to he a horizontal loop avoiding the hassle and loss related to a CP antenna.
On Sun, Nov 20, 2022 at 09:39 PM, Matt Wagner wrote:
I like RFI-EMI-GUY's recommendation of setting up a pair of receivers fed into a voter -- although building a CP antenna and setting up a receive voter is _two_ projects in one...
?
From what I've seen, Comprod makes a circularly polarized antenna, the 205-70, but doesn't really hype it any:
?
by VE3BYT and VE3KL describes the Skew-Planer antenna, which looks a lot like the cloverleaf antenna seen in 5.8 GHz drones and such. They note difficulty stacking them with anything metallic; it's unclear if this is a unique challenge with this design, though.
?
I think being able to stack a few of them in an array would be helpful, especially since a singular one effectively has -3 dB gain. Could be a fun little antenna project.
Neil you're not the only one! I've tried getting some information from the manufacturers on CPs and got almost nothing.
I do know however that a North Texas group took a DB420 and rotated the dipole elements 90¡ã to horizontal with each pair out of phase at 180¡ã. This meant one dipole on the left was rotated 90¡ã over while the other dipole on the other side was rotated 90¡ã toward the viewer.? All bays were done this way...A pattern check showed an almost perfect horizontal pattern. DB would not acknowledge it because it was modification of their design and they had no intent on trying to prove it one way or the other. If you need more info you could email me direct
?
Chris WB5ITT?
?
?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?
?
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?
?
?
?
?
?
?
--
The Real RFI-EMI-GUY
|
Will a voter switch fast/often enough to keep up with the flutter style fading? Good question. Simple answer: no, generally speaking, a regular SNR voter and two separate cross-polarized antennas won't be effective in combatting mobile flutter. The rate of mobile flutter is primarily a function of two things; the relative velocity of the stations (in the case of a repeater, only the mobile is moving), and the wavelength (the shorter the wavelength, the faster the flutter for a given velocity). A voting comparator designed to specifically deal with mobile multipath flutter could be designed, and back in the AMPS cellular days, such designs were effective, but the voting was not based on comparing relative SNR's in the audio domain like a typical two-way voter does. To others that have commented: at any instant of time, there is no guarantee that that, at any instant in time or space, multipath experienced at the receiver is being caused by cross-polarization. That is, don't assume that simply having two linear cross-polarized antennas, or even a single circular polarized antenna, is going to magically cure multipath. CP helps to address polarization skew caused by reflections, but the reflections are still there - there can, and will, still be destructive cancellation that can't be avoided regardless of whether the receiving antennas is linear or cpol. And of course, whenever a CP signal is reflected, its polarization sense is inverted, so a mobile CP antenna absolutely does not help deal with multipath if the repeater is also CP. The US is one of the countries that regularly uses CP on FM broadcast, and to a lesser extent on TV, but it's certainly not a worldwide standard. Many countries, including most of Eu, use linear polarization. There have been a lot of studies done on the subject of reception of Vpol vs Hpol vs Cpol vs slant-pol transmitted signals using linearly-polarized receiving antennas, often with conflicting results. Bottom line: CP can help in some situations, but it's not a magic cure. I'm not trying to dissuade anyone from experimentation, just have reasonable expectations on what you'll achieve. --- Jeff WN3A -- This email has been checked for viruses by Avast antivirus software. www.avast.com
|
Matt, I used a circularly polarized antenna on the WA6TDD repeater back in the 70's and early 80's. The antenna was a single bay antenna made specifically for the repeater by the JAMPRO antenna Company as a test for the 2-way world. It even has de-icers!? If you're familiar with the JAMPRO Penetrator antenna, this was the same antenna with the exception that it was center mounted; the mast was straight down below the white insulator at the feed point. This replaced a (linear) Phelps Dodge 4.8 dB gain Super-Duper Storm Master antenna.? The gain went from approximately +4.8 db to - 3 dB.? The ERP went from 100 watts to approximately 13 watts. Just to clarify, the repeater transmit was now circular and all of the users were linear; none of the users were circular.? The difference in coverage of transmit was amazing. For example: at the time I worked in a 33 story building with 6 levels of underground parking. With the linear antenna I was able to copy the repeater with its 100 watts ERP about 25 feet into the parking entrance and that was it. With the circular antenna on the repeater and a 19" spike on the top of my car I was able to copy the repeater solid down to the 2nd level and hear it spotty down to the 5th level.? At some places on the 5th level I could find spots that were almost full quieting.? People that listened to the repeater with radios like the old Patrolmen type receivers claimed that they no longer had to place their receivers near the window and fiddle with the antenna, they could now take the radio anywhere in their homes and hear the repeater with no problems. It was solid through areas like the Santa Ana Canyon and Sepulveda Pass. What was rather humorous and showed a lack of understanding by some users, who were upset that the repeater was no longer ""60 over S9," it was now only "20 over S9." The fact that it had better coverage and penetration was not the point! Now for the bad news.? It didn't hear very well.? It simply had too small an aperture. While stations could hear the repeater better than ever, and had been solid into the repeater with the 4.8 dB gain linear antenna, they? were now not so solid.? Handhelds that had no problems now had problems.? We eventually went back to the Phelps Dodge Linear antenna. What did we learn?? We learned that circular transmit to linear receive is a plus.? Yes, circular to circular is best, but not very practical. Think about putting a circularly polarized antenna on your car or handheld radio. If you have a circularly polarized antenna that truly commutates, it will be optimally coupled to a linear receive antenna even when the polarization of the signal as received is "spun" due to bounces and other propagation anomalies. It really works! You can read more about this at ? download and read the pdf file. Hopefully attached is a picture of the Antenna that JAMPRO build for the WA6TDD Repeater. Burt, K6OQK 
|
Adding to what Jeff said. For the example of the JPS-SNV-12 the default switching interval is 250 msec so that switching is at a syllabic rate. It can be set as short as 50 msec but then those switch transitions become as annoying as the mobile multipath flutter.? The voter is designed to select the antenna/receiver with lowest noise (FM Mode). If for example the normally vertical polarized signal is received predominantly in horizontal plane via diffraction then the signal received at the horizontal antenna will be stronger than the normal antenna. The multipath flutter will still be present, however the nulls will not be as noisy.?
Multipath flutter sounds quite different at 10 meters as it does at 70 CM or 800 MHz. So if working the lower frequency bands perhaps some experimentation might yield a closer transition to null ratio.?
5.5 SNR Voting and Noise-Only (FM Mode) Voting
Each Site Voter Module uses a Digital Signal Processor to continuously measure the signal and noise levels of the audio input from each receiver site. The signal measurement is made in the 300 to 800 Hz band by a JPS Interoperability Solutions proprietary speech detection and measurement algorithm. The SNV-12 measures not only the energy in this range, but also the amount of syllabic activity. Speech syllables do not consist of continuous energy, but occur at predictable rates and with predictable harmonic content. Noise is measured in the frequency band above 2200 Hz, again using a spectral approach. The Signal to Noise Ratio (SNR) is calculated from the amplitude of calculated signal divided by the amplitude of the noise. The SNR measurement operates from -6 dB to +40 dB. FM systems work best if only the noise
measurement is used for the selection of the best site, while the SNR measurement provides optimal voting performance in more noisy AM and HF systems.
The SNV-12 DSP algorithms are designed to vote speech and noise signals. For this reason the unit¡¯s voting capability cannot be verified by injecting test tones into the receive audio inputs.
In order for a new site to be voted, one SVM must detect a (selectable) better noise level or SNR than the presently voted site, and maintain this difference for a selected voting transition time.
Factory defaults for these settings are 1 dB noise level/SNR difference and a 250 msec voting transition time. This means that if site A is presently voted, site B must maintain a 1 dB noise or SNR advantage over site A for at least 250 msec. in order to be voted in place of site A. Other ¡°voting criteria¡± may be selected to fine-tune system performance. Since the majority of voting systems use FM receivers, the factory default voting method is FM Mode. This voting mode is also recommended whenever low to mid-range tones (below 2.2 kHz) are introduced into the audio spectrum for signaling purposes.
To set the SNV-12 to vote based on SNR (AM/HF mode), a dipswitch must be set on each SVM. Note: All SVMs in a chassis must be set for the same mode; there cannot be a mixture of FM and AM/HF settings on the modules.
5.6 Voting Transition Criteria
The SNV-12 will react and vote immediately when signals appear on a previously inactive system (when the voter changes from all sites squelched to one or more sites unsquelched). An adjustable delay timer sets when a voting transition can occur within a system that is currently active (one site already voted). The voting delay settings are from 50 msec to 5 seconds. The purpose of longer delays is to restrict the number of voting transitions that occur when signal conditions vary rapidly. This voting delay time is set by CPM module switch SW4, a 16-position rotary switch.
In order to be voted over the presently voted site, a new site must also maintain a noise or SNR advantage over the presently voted site for the selected transition time. This signal quality level is adjustable, and set by CPM dipswitches SW2-1, 2, 3. See Section 3 for more information on the noise and SNR differences, and on voting delay settings.
toggle quoted message
Show quoted text
On Mon, Nov 21, 2022 at 11:52 AM, Eric wrote:
Will a voter switch fast/often enough to keep up with the flutter style fading?
?
Eric
WB6TIX
On Mon, Nov 21, 2022, 09:00 RFI-EMI-GUY < rhyolite@...> wrote: Actually, My suggestion is for the second antenna to he a horizontal loop avoiding the hassle and loss related to a CP antenna.
On Sun, Nov 20, 2022 at 09:39 PM, Matt Wagner wrote:
I like RFI-EMI-GUY's recommendation of setting up a pair of receivers fed into a voter -- although building a CP antenna and setting up a receive voter is _two_ projects in one...
?
From what I've seen, Comprod makes a circularly polarized antenna, the 205-70, but doesn't really hype it any:
?
by VE3BYT and VE3KL describes the Skew-Planer antenna, which looks a lot like the cloverleaf antenna seen in 5.8 GHz drones and such. They note difficulty stacking them with anything metallic; it's unclear if this is a unique challenge with this design, though.
?
I think being able to stack a few of them in an array would be helpful, especially since a singular one effectively has -3 dB gain. Could be a fun little antenna project.
Neil you're not the only one! I've tried getting some information from the manufacturers on CPs and got almost nothing.
I do know however that a North Texas group took a DB420 and rotated the dipole elements 90¡ã to horizontal with each pair out of phase at 180¡ã. This meant one dipole on the left was rotated 90¡ã over while the other dipole on the other side was rotated 90¡ã toward the viewer.? All bays were done this way...A pattern check showed an almost perfect horizontal pattern. DB would not acknowledge it because it was modification of their design and they had no intent on trying to prove it one way or the other. If you need more info you could email me direct
?
Chris WB5ITT?
?
?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?
?
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?
?
?
?
?
?
?
--
The Real RFI-EMI-GUY
? -- The Real RFI-EMI-GUY
|
Hi Neal,
Did you get my off net response re a slot antenna?
Not the Long Alford Slot as it is narrow bandwidth thus hard to build (for us tinkerers.)
Alan VK2ZIW
On Mon, 21 Nov 2022 00:10:15 +0000 (UTC), neal Newman via groups.io
wrote
> ?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.
>
---------------------------------------------------
Alan VK2ZIW
Before the Big Bang, God, Sela.
OpenWebMail 2.53, nothing in the cloud.
|
For everybody's benefit, here is an excellent explanation originally to me,from a chief broadcast engineer friend (with his permission)---John
---------- Original Message ----------
From: Charles Dube <cld@...>
To: JOHN HASERICK <jhaserick84@...>
Date: 11/22/2022 10:18 AM
Subject: Re: Re: [repeater-builder] Circularly-polarized antennas for two-way?
Good morning John-
I'm quite familiar with these designs. We use a similar Jampro out at our Williamstown translator-
And I use single bay CP antennas at several other locations because of cost. More on that later.
Aside from height, which is probably the most important factor in FM antennas, gain is established through
varying bay distance (standardized to 1/2 and full wavelengths apart) and amount of bays.
We also have to factor in human exposure, so in the case of Williamstown we operate 2-bay, 1/2 wave spacing which gives us a 0.7 dB gain factor. If it were full wave spaced the gain would be 1.0 dB, BUT with more downward radiation, which on a building top was not permissible in this case. Regardless, we could only have one ERP factor, so it just means more transmitter power out into a less efficient antenna that alos has less downward radiation. Something broadcasters have to deal with that most repeater systems don't.
The single bay antenna has indeed a 0.46dB gain factor, so more TPO is needed.
CP does have the advantage in broadcasting in serving more receiver antenna styles, from vertical car whips to home T-dipoles (horizontal) to clock radio power cords which are random pol, if there is such a term LOL.
The pattern from a single bay CP antenna is theoretically a globe, so you waste energy up and down the tower- unless your reaching aircraft and illegal campers has any merit. But often it's a compromise in broadcasting because tower space rental is pricy, and often a single bay with more TPO is less expensive than a two or three bay (which could easily use 10-20' of towers space, which could run $1500-5000+ rental depending on market.) It just means you need a bigger transmitter, as long as the antenna is up high enough to pass radiation exposure restrictions.
But for amateur use where few if any are running horizontal polarity, there is no reason to employ CP.
And yes, that reduced gain factor has a big impact on reception. I have used CP antennas for reception
in emergency situations (because they were already at hand and mounted high) and the results are what you'd expect- not stellar. They worked, but only as a temporary solution.
Chuck
From: JOHN HASERICK <jhaserick84@...>
Sent: Monday, November 21, 2022 5:13 PM
To: Charles Dube <cld@...>
Subject: Fwd: Re: [repeater-builder] Circularly-polarized antennas for two-way?
Thought you would be interested in this, Chuck, although you are probably using circular polarization and are well aware of the reasons, but new to me
John.
---------- Original Message ----------
From: Burt K6OQK <biwa@...>
Date: 11/21/2022 12:58 PM
Subject: Re: [repeater-builder] Circularly-polarized antennas for two-way?
[Edited Message Follows] Matt,
I used a circularly polarized antenna on the WA6TDD repeater back in the 70's and early 80's. The antenna was a single bay antenna made for the repeater by the JAMPRO antenna Company as a test for the 2-way world. It even has de-icers!? If you're familiar with the JAMPRO Penetrator antenna, this was the same antenna with the exception that it was center mounted; the mast was straight down below the white insulator at the feed point. This replaced a (linear) Phelps Dodge 4.8 dB gain Super-Duper Storm Master antenna.? The gain went from approximately +4.8 db to - 3 dB.? The ERP went from 100 watts to approximately 13 watts. Just to clarify, the repeater transmit was now circular and all of the users were linear; none of the users were circular.?
The difference in coverage of transmit was amazing. For example: at the time I worked in a 33 story building with 6 levels of underground parking. With the linear antenna I was able to copy the the repeater with its 100 watts ERP about 25 feet into the parking entrance and that was it. With the circular antenna on the repeater and a 19" spike on the top of my car I was able to copy the repeater solid down to the 2nd level and hear it spotty down to the 5th level.? At some places on the 5th level I could find spots that were almost full quieting.? People that listened to the repeater with radios like the old Patrolmen type receivers claimed that they no longer had to place their receivers near the window and fiddle with the antenna, they could now take the radio anywhere in their homes and hear the repeater with no problems. It was solid through areas like the Santa Ana Canyon and Sepulveda Pass. What was rather humorous and showed a lack of understanding by some users, who were upset that the repeater was no longer ""60 over S9," it was now only "20 over S9." The fact that it had better coverage and penetration was not the point!
Now for the bad news.? It didn't hear very well.? It simply had too small an aperture. While stations could hear the repeater better than ever, and had been solid into the repeater with the 4.8 dB gain linear antenna, they? were now not so solid.? Handhelds that had no problems now had problems.? We eventually went back to the Phelps Dodge Linear antenna.
What did we learn?? We learned that circular transmit to linear receive is a plus.? Yes, circular to circular is best, but not very practical. Think about putting a circularly polarized antenna on your car or handheld radio.
If you have a circularly polarized antenna that truly commutates, it will be optimally coupled to a linear receive antenna even when the polarization of the signal as received is "spun" due to bounces and other propagation anomalies. It really works!
You can read more about this at ? download and read the pdf file.
Hopefully attached is a picture of the Antenna that JAMPRO build for the WA6TDD Repeater.
Burt, K6OQK
|
Matt Wagner
RFI-EMI-GUY
Don Clark
Chris Boone WB5ITT
Burt K6OQK