V pol over water works better than H pol (less reflections, more
absorption).
Rain drops are longer on the horizontal axis, so V pol works better
there as well.
"In a real environment the correlation between the orthogonal received
polarizations depends both on the transmitted polarization and the
extent of scattering of the signal in the transmission path. The
difference between transmitted vertical (0°) and 45° polarizations
arises because buildings present predominantly vertical reflecting
surfaces and refracting edges; ground reflection of a vertically
polarized signal does not couple the signal to horizontal polarization.
A polarization of +45° couples to -45° at each reflection at walls or on
the ground. In general, in a rural environment there will be fewer
scatterers and their characteristics will be different from scatterers
in cities.
*/Comparative Diversity Gain Using Space and Polarization Diversity /
* Several experimental comparisons between space diversity and
polarization diversity in mobile radio systems have been reported. The
results show broad qualitative agreement; the classification of
environments is approximate and may account for some of the
discrepancies between investigations. An urban environment in downtown
Chicago is entirely different from one in Paris, France or Melbourne,
Florida. Suburban means one thing in Denver, Colorado and something
entirely different in terms of the height and density of buildings in
Hope, Arkansas or Stockholm, Sweden. Similarly, rural does not
distinguish forested area, cornfields, mountains or flat plains. When
specific locations are mentioned by investigators, their classification
often appears to be very arbitrary. No reference is made to the height
of buildings or the presence of trees or open spaces in many cities.
Results from a well-documented study in Stockholm, Sweden4 are shown in
*Table 1* . These results are typical of several studies in that
polarization diversity usually appears slightly inferior to space
diversity.10 As expected from the previous discussion, polarization
diversity using a receive antenna polarization of ±45° is superior to
that obtained when the receiving antennas are horizontally and
vertically polarized. Space diversity provides higher diversity gain in
urban areas than it does in other environments, which might be expected
since there are more scatterers in urban environments and a maximal
ratio combiner will make use of all the received signal energy added
coherently."
http://www.microwavejournal.com/articles/2844-polarization-diversity-antennas-for-compact-base-stations
--
Josh Reynolds
CIO, SPITwSPOTS
www.spitwspots.com
On 03/07/2015 05:17 PM, George Skorup (Cyber Broadcasting) wrote:
I thought the whole idea of slant was chain equalization and certain
types of multipath are handled better. Take the PMP450 for example. On
5GHz (H/V), if we get a strong interferer on v-pol (all the FSK out
there) and V SNR is 15 while H SNR is 30, you get MIMO-A. With the
slant, now your V pol interferer affects both - and + 45 equally, so
you might get a SNR of 18 on both polarities, but you're still getting
MIMO-B. Dual 16QAM is better than single.
On 3/7/2015 7:14 PM, Ken Hohhof wrote:
I’m not sure that’s true unless the AF does some sort of noise
cancelling algorithm, which maybe it does. But I don’t see where the
antennas alone accomplish that. Yes, +45 would see V at –3dB, but it
would also see H at –3dB, and assuming they are uncorrelated, the
addition puts you right back where you started.
*From:* Josh Luthman <mailto:[email protected]>
*Sent:* Saturday, March 07, 2015 6:55 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Typical improvement when using 45* slant
Ahh I see what you're saying.
Josh Luthman
Office: 937-552-2340
Direct: 937-552-2343
1100 Wayne St
Suite 1337
Troy, OH 45373
On Mar 7, 2015 7:53 PM, "Jerry Richardson" <[email protected]
<mailto:[email protected]>> wrote:
The slants will be for the AF5X which will see the rockets -3dB
less than if the AF5X was on H/V
*From:*Af [mailto:[email protected]
<mailto:[email protected]>] *On Behalf Of *Josh Luthman
*Sent:* Saturday, March 07, 2015 4:41 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Typical improvement when using 45* slant
Rockets don't decide the slant/linear. The antenna does. So
those "HV Rockets" on the 45* antenna aren't HV at all.
Josh Luthman
Office: 937-552-2340 <tel:937-552-2340>
Direct: 937-552-2343 <tel:937-552-2343>
1100 Wayne St
Suite 1337
Troy, OH 45373
On Sat, Mar 7, 2015 at 7:25 PM, Jerry Richardson
<[email protected] <mailto:[email protected]>> wrote:
I see I’m not ‘splaining myself adequately
On a given tower, if I have some rockets (H/V) and I use a 45
degree antenna, I should see additional S/N of x (3dB was my
guess) between the two systems.
While that +3db would be welcome, I’m not counting it.
*From:*Af [mailto:[email protected]
<mailto:[email protected]>] *On Behalf Of *Josh Luthman
*Sent:* Saturday, March 07, 2015 3:50 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Typical improvement when using 45* slant
Radios are different, but slant vs pol won't get you
different signals.
Josh Luthman
Office: 937-552-2340 <tel:937-552-2340>
Direct: 937-552-2343 <tel:937-552-2343>
1100 Wayne St
Suite 1337
Troy, OH 45373
On Mar 7, 2015 6:38 PM, "Jerry Richardson"
<[email protected] <mailto:[email protected]>> wrote:
Looking to put in an AF5X with the 45deg slant antennas.
Was curious if we would see any additional link
improvements over the H/V Rockets.
I’m just assuming we won’t to error on the side of caution.
*From:* Af [mailto:[email protected]
<mailto:[email protected]>] *On Behalf Of *Jon Langeler
*Sent:* Saturday, March 07, 2015 3:20 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Typical improvement when using 45*
slant
if you have any links with oddball H/V signals, dual
slant would level them out a bit to be about the same on
each polarity.
Sent from my iPhone
On Mar 7, 2015, at 12:34 PM, Jerry Richardson
<[email protected] <mailto:[email protected]>> wrote:
Looking at using AF5X for a link with the 34dB 45* slants
What kind of improvement would you expect to see over
standard V/H polarization? +3dB? +6dB?
Thanks!
