[VHFcontesting] Polarization Isolation

[Michael Sapp]

Hi All:  With respect to the question concerning horizontal versus vertical 
polarization and the practical effect in amateur radio communication, just 
take a look at how commercial satellites make use of vertical and 
horizontally polarized channel allocations to get the most use out of 
limited transponder bandwidth resources.

"The Electronics Handbook - Page 1659
Jerry C. Whitaker - 1996 - ‎Preview - ‎More editions
Beam and polarization isolation: Frequency reuse allocates the same bands to 
several independent satellite transponder channels. The only way these 
signals can be kept separate is to isolate the antenna response for one 
reuse channel in the direction or polarization ... Isolations of 27-35 dB 
are typical for reuse systems."

(Search terms for this reference: ( "satellite transponder"  channel 
"polarization isolation" dB )

Keep in mind a satellite dish is a high gain antenna, and the polarization 
(horizontal, vertical, circular/elliptical) is closely controlled.  The 
effect with typical amateur antennas is more noticeable with stacked 
antennas and properly isolated transmission lines.  For example, my 4 
stacked halos on 430~450 MHz are "very horizontal" when each is properly 
matched with a balun (which tends to limit vertically polarized line 
radiation) and properly stacked.  I have difficulty getting into local FM 
repeaters with the 430~450MHz stacked halos that are up 50 feet and used on 
my 432.322 MHz weak signal cw beacon. Yet, I routinely get weak signal 
beacon reports from KU8Y near Chicago for my 432MHz beacon near Pittsburgh.

One other thing to remember is that for each antenna side lobe in an antenna 
pattern, the polarization switches. You can use this to an advantage if you 
have a horizontal yagi antenna and want to communicate more effectively with 
a station (stuck with) using vertical polarization---just use a vertically 
polarized side lobe of your horizontal yagi. Usually there will be a 
vertical side lobe at some angle off the back of the yagi antenna. It takes 
a bit of practice to find the vertical lobe, but it works and the technique 
can allow you to pull that 10 watter out of the noise in a VHF contest using 
his quarter wave vertical on 144, 222, or 432 MHz horiz ssb/cw mode....

73, Mike wa3tts

> On Sun, Jan 29, 2017 at 10:38 AM, Buddy Morgan via VHFcontesting
> <vhfcontesting at contesting.com> wrote:
>
>> Of course, I am horizontally polarized.
>
>
> Undoubtedly, that makes a difference ... but how much?
>
> Does anyone have a scholarly (or even semi-scholarly, e.g., QEX, QST)
> citation for the amount of attenuation?  I've heard anywhere from 3 dB
> to 30 dB (and WAGs going even higher).  3 to 30 dB doesn't seem like
> much to a lot of hams because they don't understand dB, but that's
> 2x(ish)  to 1000x ...  so I'm thinking one of them is wrong ... and
> since we all routinely hear signals of the other polarity I'm thinking
> it's closer to 3 than 30 ...
>
> Someone has surely done actual research on this.  So where is it?
>
>
> -- 
> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
>
>
> ------------------------------
>
> Message: 2
> Date: Sun, 29 Jan 2017 12:30:05 -0600
> From: <w5prchuck at gmail.com>
> To: Peter Laws <plaws0 at gmail.com>, vhf contesting
> <vhfcontesting at contesting.com>
> Subject: Re: [VHFcontesting] Attenuation from polarity mismatch (Re:
> C6AFP SixMeter Beacon
> Message-ID: <588e34ae.0dabca0a.89eaf.e377 at mx.google.com>
> Content-Type: text/plain; charset="utf-8"
>
> The answer is: ?It depends.?  In a perfect world, no power would be 
> transferred.  The number I see most often for the real world is 20db.
>
> Chuck W5PR