RE: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Jeff DePolo]

> >In my experience, cross-polarized antenna systems (those with
> >simultaneous in-phase vertical and horizontal components)
> 
> Isn't that just diagonal polarization? You can't have multiple linear 
> polarization orientations; that's the whole point of circular 
> polarization.
> 
> Bob NO6B

Very astute question there Bob, and there are actually two schools of
thought (and the associated debates) on that very matter.  If the two
radiators could be considered point sources that are coincident, then yes,
you'd have slant polarization due to the E&M fields adding directly.  If you
don't assume them to be coincident sources, then you just have two
orthogonal linear polarizations that can be treated separately.  That's the
simplified version of the way most seem to view the topic, but the grey area
comes when you try to gauge "how close is close enough to consider them to
be concicident".

In most dual-polarization (non-circular, non-elliptical) FM arrays, there is
little attention paid to coincidence of the radiators, and due to pattern
distortion caused by the mounting structure, or even due to intentionally
combining a non-directional radiator of one polarization with a directional
radiator of another polarization, treating them as separate Hpol and Vpol
radiators/fields is likely a more realistic approximation.  As such, Steve's
comment about mixed linear polarizations yielding less predicable results
than true Cpol/Epol are on the money.

--- Jeff WN3A

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[no6b]

At 9/5/2010 08:23, you wrote:

>In my experience, cross-polarized antenna systems (those with
>simultaneous in-phase vertical and horizontal components)

Isn't that just diagonal polarization?  You can't have multiple linear 
polarization orientations; that's the whole point of circular polarization.

Bob NO6B

[Repeater-Builder] Re: Circular polarization for VHF repeaters?

[sbjohnston]

WN3A wrote:

>That's pretty much correct, but there are many stations that have a 
vertical
>component added that isn't necessarily part of a circularly-polarized 
array.

The discussion was about circularly-polarized antenna arrays, so my 
comments were completely correct - not "pretty much".  -grin-

In my experience, cross-polarized antenna systems (those with 
simultaneous in-phase vertical and horizontal components) can make 
multipath cancellations worse, not better.   Depends to some degree on 
the nature of the objects causing the reflections, I'm sure, and 
whether or not the two antenna components are fed in a controlled way 
or just excited by being in the field of the main element.

Circular does not have this drawback, as at any given instant it is 
just one polarization.

Steve  WD8DAS

RE: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Jeff DePolo]

> >It looks like the FCC rules give you extra power when opting for dual
> >polarization. 

No, they don't give you "extra" power.  For commercial stations, horizontal
polarization is the standard.  You can supplement it with vertical, either
as cross-polarized linear, or as elliptial/circular, but that Vpol
component's ERP can't exceed the Hpol ERP.

For non-commercial stations in the reserved band (i.e. below 92 MHz) within
the affected area of a channel 6 station, there are many cases where they
are authorized for more Vpol than Hpol to protect channel 6 (which is
presumed to always be horizontally polarized).

The only "extra" power you get is additional transmitter power output (TPO)
due to the reduced antenna gain (assuming the number of bays remains the
same, and the same bay spacing) when you go from horizontal polarizaton to
mixed polarity.

> That's a confusing point, I know. Every circularly-polarized FM 
> station I've seen (and that's a lot of them) use an antenna 
> design that 
> handles the phasing and "time-delay" to create the 
> circularly-polarized 
> signal. 

That's pretty much correct, but there are many stations that have a vertical
component added that isn't necessarily part of a circularly-polarized array.
The vertical may be added as a separate radiator, but not phased with the
Hpol radiators to yield circular, so you just have two non-coherent linear
polarizations.  Or a single linear radiator may be tilted to give "slant"
polarization, which the FCC will accept as having both an Hpol and Vpol
component, with the ratio being a function of the tilt angle.

> The license reference to H and V powers (regarding c-pol station) is 
> intended to say how much ERP should some out when the signal is V and 
> how much when it is H. It is possible to make the two components 
> different, resulting in elliptical polarization rather than circular.

They can be different, and yet not be elliptical.  If they aren't phased
together to yield a coherent rotation at all azimuthal angles, it's just
random cross-polarization, not elliptical.
 
99% of the current topic was covered a year or so ago on this list - might
want to revisit the archives.

For those thinking about building Cpol bays, I'd suggest starting out with
something simple like a ring-stub.  Easy to make with a tubing bender (or
Armstrong method), feed with a gamma, DC-ground at the mounting bracket at
the rear of the bay, decent pattern circularity (but not great axial ratio
symmetry), cheap and easy way to start.  For those not familiar, a ring stub
bay looks like this (I don't recommend OMB, it's just a decent picture of a
very basic ring stub bay):  

http://www.omb.com/en/index.php?option=content&task=view&id=78&Itemid=38 

Ring stubs are sometimes also called "cycloids" (albeit sometimes
erroneously), often built with a balanced feed.  You can try Googling
"cycloid", "ring stub FM antenna", etc. for more pics and design ideas or
email direct.

--- Jeff WN3A

RE: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Kris Kirby]

On Fri, 3 Sep 2010, Kris Kirby wrote:
> > Once you get it figured out, PLEASE write up an article for 
> > Repeater-Builder for the rest of us!!
> 
> Make an "X" with dipole elements, and connect the feed harness to one 
> side, and connect the left and right sides together with 
> 1/4-wavelength of coax, wire, or coat-hanger. The antenna elements 
> should be on opposite sides of the mast.
> 
> Something about this tells me that the stack should have the next 
> section up rotated 90-degrees around vertical to eliminate nulls.
> 
> If you take that and try to build it all around the same point, it 
> starts looking like an imploded Lindenblad.

I could go further to say that it should be possible to do this with two 
DB-224 clones, the ones that hold the elements to the pipes with 
hose-clamps. Connect up all the feed harnesses as you normally would and 
connect the two by a -90 degree hybrid, or a 0-degree (in-phase) 
Wilkinson divider with a -90 degree section (1/4-wavelength) of coax on 
one leg, so that one antenna is fed -90 degrees (1/4-wavelength) from 
the other. 

Pasternak's article makes mention that these antennas are difficult to 
match. Things being as critical as they are, I would recommend tuning 
for minimum VSWR, since the receivers are hardly ever 50-ohms. 

This antenna may lend itself better to a split-antenna system without 
much separation between the circular antenna and the vertical antenna -- 
simply to avoid detuning the receiver duplexers if the antenna loading 
situation changes due to ice or other effects. 

--
Kris Kirby, KE4AHR
Disinformation Analyst

RE: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Kris Kirby]

On Fri, 3 Sep 2010, Mark wrote:
> Once you get it figured out, PLEASE write up an article for 
> Repeater-Builder for the rest of us!!

Make an "X" with dipole elements, and connect the feed harness to one 
side, and connect the left and right sides together with 1/4-wavelength 
of coax, wire, or coat-hanger. The antenna elements should be on 
opposite sides of the mast. 

Something about this tells me that the stack should have the next 
section up rotated 90-degrees around vertical to eliminate nulls.

If you take that and try to build it all around the same point, it 
starts looking like an imploded Lindenblad.

--
Kris Kirby, KE4AHR
Disinformation Analyst

RE: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Mark]

Gary,

Once you get it figured out, PLEASE write up an article for Repeater-Builder
for the rest of us!!

Mark - N9WYS

-Original Message-
From: Repeater-Builder@yahoogroups.com  On Behalf Of Gary - K7EK

Thanks to all that replied. I appreciate your input. I'm still looking for
answers, but may be onto something.  I have emailed Bill Pasternak, the
author of that Cushcraft 4-pole conversion article. I re-read his original
article and may have figured out what I must do. That, plus any additional
input from Bill, should hopefully help me to complete the project. 

I will post again later if I have any success.

Best regards,

Gary, K7EK

Personal Web Page:  www.k7ek.net 

[Repeater-Builder] Re: Circular polarization for VHF repeaters?

[sbjohnston]

>It looks like the FCC rules give you extra power when opting for dual
>polarization.  Doesn't mean the circular antenna contributes to extra
>coverage, in fact it looks like the extra RF power allowed for the two
>polarities is giving you more coverage?

That's a confusing point, I know.  Every circularly-polarized FM 
station I've seen (and that's a lot of them) use an antenna design that 
handles the phasing and "time-delay" to create the circularly-polarized 
signal.  It is generally not done with separate horizontal and vertical 
antennas, another transmitter and phasing in the transmitter building, 
or anything like that.

Think of it this way - a circularly-polarized signal is "spinning" as 
the signal goes thru each RF cycle.  At any given moment it is rushing 
 from vertical thru various diagonal polarizations to horizontal and 
back around again.

The license reference to H and V powers (regarding c-pol station) is 
intended to say how much ERP should some out when the signal is V and 
how much when it is H.  It is possible to make the two components 
different, resulting in elliptical polarization rather than circular.

A VHF repeater could use the same antenna concepts (usually crossed 
dipoles with a phasing harness) to produce circular polarization.  Have 
a look at circularly-polarized satellite antenna designs.

Steve  WD8DAS

sbjohns...@aol.com
http://www.wd8das.net/

Radio is your best entertainment value.

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Kris Kirby]

On Fri, 3 Sep 2010, Gary - K7EK wrote:
> Thanks to all that replied. I appreciate your input. I'm still looking 
> for answers, but may be onto something.  I have emailed Bill 
> Pasternak, the author of that Cushcraft 4-pole conversion article. I 
> re-read his original article and may have figured out what I must do. 
> That, plus any additional input from Bill, should hopefully help me to 
> complete the project.
> 
> I will post again later if I have any success.
> 
> Best regards,
> 
> Gary, K7EK
> 
> Personal Web Page:  www.k7ek.net

If you find a copy out on the 'net, please forward me a copy of the 
link.

--
Kris Kirby, KE4AHR
Disinformation Analyst

[Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Gary - K7EK]

Thanks to all that replied. I appreciate your input. I'm still looking for 
answers, but may be onto something.  I have emailed Bill Pasternak, the author 
of that Cushcraft 4-pole conversion article. I re-read his original article and 
may have figured out what I must do. That, plus any additional input from Bill, 
should hopefully help me to complete the project. 

I will post again later if I have any success.

Best regards,

Gary, K7EK

Personal Web Page:  www.k7ek.net




--- In Repeater-Builder@yahoogroups.com, "Gary - K7EK"  wrote:
>
> 
> Greetings,
> 
> I am in a particularly sticky situation with one of my two meter repeaters in 
> Lakewood, WA (Tacoma). I have generally great coverage, however there is a 
> very annoying problem with multipath and raspy signals in a large portion of 
> my coverage area. Since the Puget Sound area of Western Washington is very 
> hilly and mountainous, multipath is very damaging to all forms of VHF 
> communication.
> 
> Over the years I have read about folks employing circular polarization to 
> overcome fading, nulls, multipath, etc. There is so  very little written 
> about this topic in amateur circles so I thought I'd bring it up here and see 
> what I could come up with.
> 
> In the 80's there was a amateur radio repeater book by a fellow, Pasternak I 
> believe, that took two gamma match style Cuschcraft Four Pole antennas, 
> combined them, and did some magic with phasing lines to end up with a four 
> bay circularly polarized repeater antenna.  Unfortunately the description 
> leaves much to be desired, at least for me, so I never built one. If he would 
> have included specifics on phasing line lengths, cable types, etc, the job 
> would have been a whole lot easier. Has anyone actually gone circular with 
> Cushcraft Four Poles, and if so, could you please share it with me and/or 
> this group?
> 
> I have done some inquiring to commercial companies about a custom built two 
> meter four bay circularly polarized array, but that is entirely out of the 
> question. They want thousands of dollars. There must be an easier (and 
> cheaper) way.
> 
> Similarly, is anyone in this group running circular polarization on your 
> amateur repeater(s), and if so, could you please share the details in a 
> manner that could be duplicated without a lot of guess work? 
> 
> I know that I could easily solve my multipath problem by installing one or 
> more remote receivers, however I would like to keep that as a last resort and 
> shoot for a circularly polarized antenna system at the main repeater site.  I 
> do understand that there is approximately 3 db of loss as a result of this, 
> but that is quite acceptable. The dividends would greatly outweigh the down 
> side.
> 
> Thanks for any constructive ideas, suggestions, links, etc, that you might be 
> willing to share concerning this situation.
> 
> Best regards,
> 
> Gary, K7EK
> 
> 
>

RE: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Eric Lemmon]

I completely agree!  Back in the late 60's, I was Chief Engineer at WLRW-
the first FM station in the state of Illinois to broadcast in stereo- and
this was in Champaign-Urbana, not Chicago!  The transmitter was an RCA
BTF-10D which fed five Andrew "Vee" antennas and five Gates "Rings", giving
us about 25 kW vertical and 25 kW horizontal.  The majority of FM stations
then used horizontal polarization, for reaching FM table radios that had
line-cord antennas and component stereo systems.  AM/FM car radios became an
option around 1967, and WLRW was ready with a vertical component to better
reach car radios.

I acknowledge that dual polarization is not the same as circular
polarization, but it does accomplish what the station owner wanted back
then:  Full coverage of home and car/portable radios.  I look forward to
hearing about the changes that circular polarization can make to VHF
repeater coverage. 

73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of sbjohns...@aol.com
Sent: Thursday, September 02, 2010 6:48 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

  

FM broadcasting in the US is not changing to vertical polarization.

There may be some old stations still running horizontal, and vertical
is used in some situations (such as stations low in the band needing to
be cross-polarized from a nearby channel 6 TV signal) but circular
polarization is by far the preferred method. I've had FM stations
running both, and have a firm impression that circular is indeed better
for mobile reception. I may get the chance to convert some stations
from vertical to c-pol when the rules are changed now that the
conversion to HDTV has been made.

I may have access to some papers on the subject - I'll check.

I believe c-pol could be better for amateur VHF repeater-mobile
operations in high-multipath areas.

Steve

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Gordon Cooper]

  Thanks Paul and Kris for your suggestions.

  While 29 MHZ could well be better, we do not have that option. These 
are non-amateur operations although the base station and repeater are 
owned and operated by local amateurs. We do have a few amateurs 
scattered amongst the search teams too - but most of them are trampers, 
deerstalkers & Police using frequencies allocated for emergency work..

  We have used 440 MHZ occasionally for linking with our own group but
it falls down badly in the dense bush particularly when leaves & trees
are wet.

   So 141 MHz it is, with 5 and 3 MHZ available for longer hops - 
although rigging aerials for these is not easy in the bush.

The repeater includes a 28 AH battery - making about half the weight and
we allow for connecting an external battery (something else to carry in
by backpack or chopper) if the search goes over 4 days. The whole 
business of power consumption is helped by a semi-sleep mode, in the
absence of traffic, the repeater shuts down everything not needed for
listening. It takes 2-300 milliseconds to fire up again so our users
are told to delay  briefly between pushing the mike button and opening
their mouths.

   You mentioned 8 hours time for the portables, yep that is about right
so they carry spare batteries - particularly if they are camping out
overnight and/or have an automatic tracking GPS running off the same
battery.

I will do more experimenting with aerials thanks.

Gordon ZL1KL

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Kris Kirby]

On Thu, 2 Sep 2010, Paul Plack wrote:
> Gordon, something worth trying might be low-band.
>  
> About 20 years ago, I lived in an area where hams did course communications
> for rally events in very mountainous terrain. I remember experimenting one
> night about 2am with my partner at the other end of a heavily wooded course,
> about 12 miles end-to-end.
>  
> 444 MHz simplex, 5 watts, colinear mobile whip - no copy.
>  
> 146 MHz simplex, 5 watts, 5/8-wave mobile whip - no copy, but would barely
> break the carrier squelch.
>  
> 29.6 MHz simplex, 4 watts, FM CB conversion, 1.3m helically-wound mobile
> whip - full quieting and S9+.

Motorola Syntor Xs are relatively easy to locate, and can be programmed 
for 10m to 6m without any retuning. They were designed for 30-50MHz.

--
Kris Kirby, KE4AHR
Disinformation Analyst

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Kris Kirby]

On Thu, 2 Sep 2010, Gordon Cooper wrote:
> I guess that I do not have much to contribute on this 
> thread but to me it is very interesting reading. Gary has my sympathy, 
> his problem is duplicated here.  Much of my repeater work relates to a 
> low power portable repeater on 141 MHz. We live near a medium sized 
> mountain range which has plenty of deer and wild pigs. Hunters go 
> looking for them and perhaps get lost, or fall and break a leg. Also, 
> there are recreational trampers who just get lost . Several times a 
> year we have to go find, and rescue them. The last time was two days 
> ago at 6.30 am. For once, it was not raining!
> 
> Our repeater runs 5 watts output, needs to run three or four days off 
> a gelcell, and most importantly has to fit into a backpack to be 
> carried to a convenient hilltop.  Fortunately, the split is 3 MHz so 
> that the duplexer is of a reasonable size.

You need lower power output and a further split and a big battery. Even 
running a repeater at five watts with commercial handhelds out in the 
field (each of which have a battery that will make it for eight hours), 
you're going to need somewhere around a 33Ah battery, which weighs 25 
lbs. 
 
>The problem is getting reasonable coverage. Sure the search areas 
> are fairly small but usually encompass several ridges and deep 
> valleys. We use vertical polarisation with a 5/8 whip on the repeater 
> and the search teams have flexible dipoles that fit into their 
> backpacks. Sharp ridges and steep slopes contribute to coverage 
> problems. Would circular polarization help??  I think not.

Remember, a quarter-wave has significant energy in the pattern from 
about five degrees to eighty-five degrees; if you're dealing with 
valleys, this may be a better choice for an antenna.

--
Kris Kirby, KE4AHR
Disinformation Analyst

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Mike Morris]

There is one local UHF group that has a back-to-back 6m repeater
just for range extension.  The Scom 7330 makes the
parallel/separate link on/off mode real easy (and for up to 3 ports).

At 02:10 AM 09/02/10, you wrote:


Gordon, something worth trying might be low-band.

About 20 years ago, I lived in an area where hams did course 
communications for rally events in very mountainous terrain. I 
remember experimenting one night about 2am with my partner at the 
other end of a heavily wooded course, about 12 miles end-to-end.


444 MHz simplex, 5 watts, colinear mobile whip - no copy.

146 MHz simplex, 5 watts, 5/8-wave mobile whip - no copy, but would 
barely break the carrier squelch.


29.6 MHz simplex, 4 watts, FM CB conversion, 1.3m helically-wound 
mobile whip - full quieting and S9+.


Antennas might be a bit of a trick for portables on 10m, and a 
repeater might have to be crossband, but worth a shot.


73,
Paul, AE4KR

- Original Message -
From: <mailto:zl...@nzart.org.nz>Gordon Cooper
To: <mailto:Repeater-Builder@yahoogroups.com>Repeater-Builder@yahoogroups.com
Sent: Thursday, September 02, 2010 1:51 AM
Subject: Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

Our repeater runs 5 watts output, needs to run three or four days off a
gelcell, and most importantly has to fit into a backpack to be carried
to a convenient hilltop. Fortunately, the split is 3 MHz so that the
duplexer is of a reasonable size.

The problem is getting reasonable coverage. Sure the search areas are
fairly small but usually encompass several ridges and deep valleys. We
use vertical polarisation with a 5/8 whip on the repeater and the search
teams have flexible dipoles that fit into their backpacks. Sharp ridges
and steep slopes contribute to coverage problems. Would circular
polarization help?? I think not.





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Checked by AVG - www.avg.com
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09/01/10 11:34:00

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Chuck Kelsey]

I would agree that lower gain antennas can make a big difference in some 
instances. Higher gain mean more nulls.

Chuck
WB2EDV


  - Original Message - 
  From: petedcur...@gmail.com 
  To: Repeater-Builder 
  Sent: Thursday, September 02, 2010 10:38 AM
  Subject: Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?




  It looks like the FCC rules give you extra power when opting for dual 
polarization.  Doesn't mean the circular antenna contributes to extra coverage, 
in fact it looks like the extra RF power allowed for the two polarities is 
giving you more coverage?  The web article for which I gave a link was from 
Europe and involved IBC Israel & BBC UK tests and their conclusion was similar 
on Vertical Polarization.  
  Many lack of coverage issues I've seen with extremely high sites is due to 
the use of high gain antennas with little or no down tilt.  I have seen issues 
like this resolved by simply using a lower gain, say going from 10db gain down 
to 7 dB gain and applying 4 - 6 degrees of down tilt.  Lowering the gain widens 
the beam and addition of down tilt puts the major part of the RF signal closer 
in and that improves coverage but it still puts a signal out to the RF horizon.


  Peter






  On Thu, Sep 2, 2010 at 1:47 AM, JOHN MACKEY  wrote:

  
FM broadcast is NOT changing to vertical polarity!

Most stations today are going on the air with either circular polarity or
cross polarity (consisting of signal in BOTH the vertical and horizontal
poles)

With FCC licensing today, a FM station licensed for 10KW can have 10 KW in 
the
vertical plane and 10 kW in the horizontal plane. So there would be no 
reason
to only have the power in one plane.

In the last 3 years, I have built 2 FM stations. Both used circular or cross
polarity.



-- Original Message --
Received: Wed, 01 Sep 2010 10:32:51 PM PDT
From: petedcur...@gmail.com
To: Repeater-Builder 
Subject: Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

> Hi,
> I remembered circular polarization was used for FM broadcast due to FM car
> radios, but when I looked it up I found out some interesting facts, see 
the
> link below,
> 
>

https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134
> 
>

<https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134>Interesting
> white paper on FM Broadcast and why they had historically had circular
> polarization and why they are now changing to vertical polarization.
> 
> Peter
> 
> On Thu, Sep 2, 2010 at 1:22 AM, burkleoj  wrote:
> 
> >
> >
> > Gary,
> > I am in Southern Oregon and I understand exactly what you are
experiencing.
> > We have very similar problems down here with our club's repeater. I have
> > often talked about and even done some serious looking at remodeling a 
set
of
> > broadcast loops and harness for 2 Meters.
> >
> > I know there was a southern California repeater back in the 70's that
used
> > circular polarization with excellent results. They were able to provide
much
> > better coverage in their main service area, but did loose some long
distance
> > coverage outside their main coverage area.
> >
> > We have had the best success by using a lower gain antenna. We have been
> > using the Telewave broadband two loop antennas with 2 - 4 degrees of
> > downtilt, for both our 2 Meter and 440 MHz repeaters. I have found much
> > better close in (0-30 Miles) coverage, less muti-path, and they cost 
quite
a
> > bit less than a Super Stationmaster.
> >
> > Good Luck and keep us posted with what you find for results.
> >
> > Joe - WA7JAW
> >
> >
> > --- In

Repeater-Builder@yahoogroups.com,

> > "Gary - K7EK"  wrote:
> > >
> > >
> > > Greetings,
> > >
> > > I am in a particularly sticky situation with one of my two meter
> > repeaters in Lakewood, WA (Tacoma). I have generally great coverage,
however
> > there is a very annoying problem with multipath and raspy signals in a
large
> > portion of my coverage area. Since the Puget Sound area of Western
> > Washington is very hilly and mountainous, multipath is very damaging to
all
> > forms of VHF communication.
> >
> > 
> >
> 








  


--



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02:34:00

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[petedcurtis]

It looks like the FCC rules give you extra power when opting for dual
polarization.  Doesn't mean the circular antenna contributes to extra
coverage, in fact it looks like the extra RF power allowed for the two
polarities is giving you more coverage?  The web article for which I gave a
link was from Europe and involved IBC Israel & BBC UK tests and their
conclusion was similar on Vertical Polarization.
Many lack of coverage issues I've seen with extremely high sites is due to
the use of high gain antennas with little or no down tilt.  I have seen
issues like this resolved by simply using a lower gain, say going from 10db
gain down to 7 dB gain and applying 4 - 6 degrees of down tilt.  Lowering
the gain widens the beam and addition of down tilt puts the major part of
the RF signal closer in and that improves coverage but it still puts a
signal out to the RF horizon.

Peter



On Thu, Sep 2, 2010 at 1:47 AM, JOHN MACKEY  wrote:

>
>
> FM broadcast is NOT changing to vertical polarity!
>
> Most stations today are going on the air with either circular polarity or
> cross polarity (consisting of signal in BOTH the vertical and horizontal
> poles)
>
> With FCC licensing today, a FM station licensed for 10KW can have 10 KW in
> the
> vertical plane and 10 kW in the horizontal plane. So there would be no
> reason
> to only have the power in one plane.
>
> In the last 3 years, I have built 2 FM stations. Both used circular or
> cross
> polarity.
>
>
> -- Original Message --
> Received: Wed, 01 Sep 2010 10:32:51 PM PDT
> From: petedcur...@gmail.com 
> To: Repeater-Builder 
> 
> >
> Subject: Re: [Repeater-Builder] Re: Circular polarization for VHF
> repeaters?
>
> > Hi,
> > I remembered circular polarization was used for FM broadcast due to FM
> car
> > radios, but when I looked it up I found out some interesting facts, see
> the
> > link below,
> >
> >
>
> https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134
> >
> >
> <
> https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134
> >Interesting
> > white paper on FM Broadcast and why they had historically had circular
> > polarization and why they are now changing to vertical polarization.
> >
> > Peter
> >
> > On Thu, Sep 2, 2010 at 1:22 AM, burkleoj 
> > >
> wrote:
> >
> > >
> > >
> > > Gary,
> > > I am in Southern Oregon and I understand exactly what you are
> experiencing.
> > > We have very similar problems down here with our club's repeater. I
> have
> > > often talked about and even done some serious looking at remodeling a
> set
> of
> > > broadcast loops and harness for 2 Meters.
> > >
> > > I know there was a southern California repeater back in the 70's that
> used
> > > circular polarization with excellent results. They were able to provide
> much
> > > better coverage in their main service area, but did loose some long
> distance
> > > coverage outside their main coverage area.
> > >
> > > We have had the best success by using a lower gain antenna. We have
> been
> > > using the Telewave broadband two loop antennas with 2 - 4 degrees of
> > > downtilt, for both our 2 Meter and 440 MHz repeaters. I have found much
> > > better close in (0-30 Miles) coverage, less muti-path, and they cost
> quite
> a
> > > bit less than a Super Stationmaster.
> > >
> > > Good Luck and keep us posted with what you find for results.
> > >
> > > Joe - WA7JAW
> > >
> > >
> > > --- In
> Repeater-Builder@yahoogroups.com 
> ,
>
> > > "Gary - K7EK"  wrote:
> > > >
> > > >
> > > > Greetings,
> > > >
> > > > I am in a particularly sticky situation with one of my two meter
> > > repeaters in Lakewood, WA (Tacoma). I have generally great coverage,
> however
> > > there is a very annoying problem with multipath and raspy signals in a
> large
> > > portion of my coverage area. Since the Puget Sound area of Western
> > > Washington is very hilly and mountainous, multipath is very damaging to
> all
> > > forms of VHF communication.
> > >
> > >
> > >
> >
>
>  
>

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Paul Plack]

Gordon, something worth trying might be low-band.

About 20 years ago, I lived in an area where hams did course communications for 
rally events in very mountainous terrain. I remember experimenting one night 
about 2am with my partner at the other end of a heavily wooded course, about 12 
miles end-to-end.

444 MHz simplex, 5 watts, colinear mobile whip - no copy.

146 MHz simplex, 5 watts, 5/8-wave mobile whip - no copy, but would barely 
break the carrier squelch.

29.6 MHz simplex, 4 watts, FM CB conversion, 1.3m helically-wound mobile whip - 
full quieting and S9+.

Antennas might be a bit of a trick for portables on 10m, and a repeater might 
have to be crossband, but worth a shot.

73,
Paul, AE4KR

  - Original Message - 
  From: Gordon Cooper 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Thursday, September 02, 2010 1:51 AM
  Subject: Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?


  Our repeater runs 5 watts output, needs to run three or four days off a 
  gelcell, and most importantly has to fit into a backpack to be carried 
  to a convenient hilltop. Fortunately, the split is 3 MHz so that the 
  duplexer is of a reasonable size.

  The problem is getting reasonable coverage. Sure the search areas are
  fairly small but usually encompass several ridges and deep valleys. We 
  use vertical polarisation with a 5/8 whip on the repeater and the search
  teams have flexible dipoles that fit into their backpacks. Sharp ridges 
  and steep slopes contribute to coverage problems. Would circular 
  polarization help?? I think not.

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[Gordon Cooper]

HI to all,
I guess that I do not have much to contribute on this thread 
but to me it is very interesting reading. Gary has my sympathy, his 
problem is duplicated here.  Much of my repeater work relates to a low
power portable repeater on 141 MHz. We live near a medium sized mountain
range which has plenty of deer and wild pigs. Hunters go looking for 
them and perhaps get lost,  or fall and break a leg. Also, there are 
recreational trampers who just get lost . Several times a year we have 
to go find, and rescue them. The last time was two days ago at 6.30 am. 
For once, it was not raining!

Our repeater runs 5 watts output, needs to run three or four days off a 
gelcell, and most importantly has to fit into a backpack to be carried 
to a convenient hilltop.  Fortunately, the split is 3 MHz so that the 
duplexer is of a reasonable size.

   The problem is getting reasonable coverage. Sure the search areas are
fairly small but usually encompass several ridges and deep valleys. We 
use vertical polarisation with a 5/8 whip on the repeater and the search
teams have flexible dipoles that fit into their backpacks. Sharp ridges 
and steep slopes contribute to coverage problems. Would circular 
polarization help??  I think not.

Gordon ZL1KL
Tauranga N.Z.

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[DCFluX]

FM Broadcast started out Horizontally polarized.  Circular
polarization was later authorized under 2 stipulations. The vertical
plane power can not exceed the horizontal power ERP, and the
horizontal plane ERP is used for the stations ERP. So a station with a
horizontal antenna can effectively double the ERP by switching to a
circular antenna, of course it takes 2 CP antennas to equal one
horizontal antenna.

On the receive side of things, Horizontal is usually used in homes and
Vertical or CP on cars.  CP also helps quite a bit with mobile
flutter.

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[JOHN MACKEY]

FM broadcast is NOT changing to vertical polarity!

Most stations today are going on the air with either circular polarity or
cross polarity (consisting of signal in BOTH the vertical and horizontal
poles)

With FCC licensing today, a FM station licensed for 10KW can have 10 KW in the
vertical plane and 10 kW in the horizontal plane.  So there would be no reason
to only have the power in one plane.

In the last 3 years, I have built 2 FM stations.  Both used circular or cross
polarity.

-- Original Message --
Received: Wed, 01 Sep 2010 10:32:51 PM PDT
From: petedcur...@gmail.com
To: Repeater-Builder 
Subject: Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

> Hi,
> I remembered circular polarization was used for FM broadcast due to FM car
> radios, but when I looked it up I found out some interesting facts, see the
> link below,
> 
>
https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134
> 
>
<https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134>Interesting
> white paper on FM Broadcast and why they had historically had circular
> polarization and why they are now changing to vertical polarization.
> 
> Peter
> 
> On Thu, Sep 2, 2010 at 1:22 AM, burkleoj  wrote:
> 
> >
> >
> > Gary,
> > I am in Southern Oregon and I understand exactly what you are
experiencing.
> > We have very similar problems down here with our club's repeater. I have
> > often talked about and even done some serious looking at remodeling a set
of
> > broadcast loops and harness for 2 Meters.
> >
> > I know there was a southern California repeater back in the 70's that
used
> > circular polarization with excellent results. They were able to provide
much
> > better coverage in their main service area, but did loose some long
distance
> > coverage outside their main coverage area.
> >
> > We have had the best success by using a lower gain antenna. We have been
> > using the Telewave broadband two loop antennas with 2 - 4 degrees of
> > downtilt, for both our 2 Meter and 440 MHz repeaters. I have found much
> > better close in (0-30 Miles) coverage, less muti-path, and they cost quite
a
> > bit less than a Super Stationmaster.
> >
> > Good Luck and keep us posted with what you find for results.
> >
> > Joe - WA7JAW
> >
> >
> > --- In
Repeater-Builder@yahoogroups.com,
> > "Gary - K7EK"  wrote:
> > >
> > >
> > > Greetings,
> > >
> > > I am in a particularly sticky situation with one of my two meter
> > repeaters in Lakewood, WA (Tacoma). I have generally great coverage,
however
> > there is a very annoying problem with multipath and raspy signals in a
large
> > portion of my coverage area. Since the Puget Sound area of Western
> > Washington is very hilly and mountainous, multipath is very damaging to
all
> > forms of VHF communication.
> >
> >  
> >
> 

Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?

[petedcurtis]

Hi,
I remembered circular polarization was used for FM broadcast due to FM car
radios, but when I looked it up I found out some interesting facts, see the
link below,

https://www.digitaltraders.com/index.php/index.php/components/com_kunena/template/default_ex/templates/ja_edenite/index.php?option=com_content&view=article&id=57&Itemid=134

Interesting
white paper on FM Broadcast and why they had historically had circular
polarization and why they are now changing to vertical polarization.

Peter

On Thu, Sep 2, 2010 at 1:22 AM, burkleoj  wrote:

>
>
> Gary,
> I am in Southern Oregon and I understand exactly what you are experiencing.
> We have very similar problems down here with our club's repeater. I have
> often talked about and even done some serious looking at remodeling a set of
> broadcast loops and harness for 2 Meters.
>
> I know there was a southern California repeater back in the 70's that used
> circular polarization with excellent results. They were able to provide much
> better coverage in their main service area, but did loose some long distance
> coverage outside their main coverage area.
>
> We have had the best success by using a lower gain antenna. We have been
> using the Telewave broadband two loop antennas with 2 - 4 degrees of
> downtilt, for both our 2 Meter and 440 MHz repeaters. I have found much
> better close in (0-30 Miles) coverage, less muti-path, and they cost quite a
> bit less than a Super Stationmaster.
>
> Good Luck and keep us posted with what you find for results.
>
> Joe - WA7JAW
>
>
> --- In Repeater-Builder@yahoogroups.com,
> "Gary - K7EK"  wrote:
> >
> >
> > Greetings,
> >
> > I am in a particularly sticky situation with one of my two meter
> repeaters in Lakewood, WA (Tacoma). I have generally great coverage, however
> there is a very annoying problem with multipath and raspy signals in a large
> portion of my coverage area. Since the Puget Sound area of Western
> Washington is very hilly and mountainous, multipath is very damaging to all
> forms of VHF communication.
>
>  
>

[Repeater-Builder] Re: Circular polarization for VHF repeaters?

[burkleoj]

Gary,
I am in Southern Oregon and I understand exactly what you are experiencing. We 
have very similar problems down here with our club's repeater. I have often 
talked about and even done some serious looking at remodeling a set of 
broadcast loops and harness for 2 Meters.

I know there was a southern California repeater back in the 70's that used 
circular polarization with excellent results. They were able to provide much 
better coverage in their main service area, but did loose some long distance 
coverage outside their main coverage area.

We have had the best success by using a lower gain antenna. We have been using 
the Telewave broadband two loop antennas with 2 - 4 degrees of downtilt, for 
both our 2 Meter and 440 MHz repeaters. I have found much better close in (0-30 
Miles) coverage, less muti-path, and they cost quite a bit less than a Super 
Stationmaster.

Good Luck and keep us posted with what you find for results.

Joe - WA7JAW

--- In Repeater-Builder@yahoogroups.com, "Gary - K7EK"  wrote:
>
> 
> Greetings,
> 
> I am in a particularly sticky situation with one of my two meter repeaters in 
> Lakewood, WA (Tacoma). I have generally great coverage, however there is a 
> very annoying problem with multipath and raspy signals in a large portion of 
> my coverage area. Since the Puget Sound area of Western Washington is very 
> hilly and mountainous, multipath is very damaging to all forms of VHF 
> communication.