There is a lot of information here but I agree, the document seems a bit discreet and also a bit difficult to read. I like the idea of proving that I understand something well by being able to describe it in the simplest terms possible without misrepresenting the meaning…
My take away on how it adjusts my thinking is that I was applying single chains concepts and not considering other factors at play with MIMO, mainly that you can get additional information by comparing the chains. I still don’t understand how the energy recovery through summing signals has any advantage… I take it that the simple answer is that the loss of both out of phase antenna chains is about half but two half’s make a whole... That seems logical enough assuming I am understanding things... All the more… I didn’t get the feeling that there is an advantage to this out of phase antenna configuration. Is this mismatch a good thing? Is Cambium doing it just because they can? Did they plan for cross polarity and then blackout of the decision half way as a compromise that still works? Then there is the question of how this polarity mismatch performs with varied situations of refraction, reflection, noise etc… Has anyone compared a all H&V configuration with a mix of slant and H&V in the field? Honestly my ePMP experience has been with UBNT H&V sector antennas so I haven’t played with the mix environment. So after all that I am on the same page with Paul… “To slant or not to slant”? Now that’s my question too. Sincerely, Joshaven Potter MTCNA, MTCRE, MTCWE, MTCTCE, UACA Google Hangouts: [email protected] Cell & SMS: 1-517-607-9370 [email protected] > On Dec 4, 2015, at 7:55 PM, Faisal Imtiaz <[email protected]> wrote: > > No worries, you are on the right track, and asking the right questions..... > The document, while it says a lot, it also leaves another very interesting > question unanswered, with a very casual implied answer.... > > See if you can read between the lines and figure out the 'it' ! > > :) > > (ref: Movie City Slickers .... 'it' is different for everyone ! ) > > Regards. > > Faisal Imtiaz > Snappy Internet & Telecom > 7266 SW 48 Street > Miami, FL 33155 > Tel: 305 663 5518 x 232 > > Help-desk: (305)663-5518 Option 2 or Email: [email protected] > > From: "Joshaven Mailing Lists" <[email protected]> > To: [email protected] > Sent: Friday, December 4, 2015 4:44:24 PM > Subject: Re: [AFMUG] to slant, or not to slant - that is the question > Thanks! Just the info I needed so that I can figure out how to eat my > shorts! Now I need to read this thing really carefully because my mind just > went pop. Sounds like y’all were ahead of me in this area of thinking > something was out of order… > > Sincerely, > Joshaven Potter > MTCNA, MTCRE, MTCWE, MTCTCE, UACA > Google Hangouts: [email protected] <mailto:[email protected]> > Cell & SMS: 1-517-607-9370 > [email protected] <mailto:[email protected]> > > > > On Dec 4, 2015, at 4:25 PM, Faisal Imtiaz <[email protected] > <mailto:[email protected]>> wrote: > > Since inquiring minds want to know... > > Here is the Word on this topic from Cambium... (While this was titled 2.4Ghz, > as per them, it applies to their 5ghz as well). > > :) > > Faisal Imtiaz > Snappy Internet & Telecom > 7266 SW 48 Street > Miami, FL 33155 > Tel: 305 663 5518 x 232 > > Help-desk: (305)663-5518 Option 2 or Email: [email protected] > <mailto:[email protected]> > > From: "Joshaven Mailing Lists" <[email protected] > <mailto:[email protected]>> > To: [email protected] <mailto:[email protected]> > Sent: Friday, December 4, 2015 4:15:55 PM > Subject: Re: [AFMUG] to slant, or not to slant - that is the question > The Atheros chipset differentiating between the Mimo chains does not have to > do with 45º slant vs 90º… it means that chain A and B on one radio can be > H&V or V&H while chain A and B on the other can be H&V or V&H interchangeably > with no loss because and the chip will just cross them over as needed. This > means that hooking up the antenna cables “backwards” won’t effect anything. > It doesn’t mean that the orientation of the antenna is irrelevant. > > The energy received by an antenna that is out of phase with another antenna > is much less then if it was in phase that is a principal of radio that no > chipset will ever overcome. Now… maybe you can make a magic antenna that is > “multi phased” such that it can tune in a 45º phase offset signal well. I > suspect that the Cambium equipment when properly matched will both have the > same polorization. > > I believe that if your having the same outcome on slant or not slant it would > be due to one chain being refracted. For example if your horizontal chain > was fine but the virtual chain was refracted off something such that the wave > was on or near a 45º slant then you would have the same basic performance > regardless of a standard or slant orientation. This however is a path issue > not a design characteristic of the chipset or antenna. > > FYI, linearly polarization is not a reference to the polarization being on a > vertical, horizontal or slant axis but a reference to the way the wave > propagates, circular polarization is an alternative to linear polarization > not “slant". > > > > Sincerely, > Joshaven Potter > MTCNA, MTCRE, MTCWE, MTCTCE, UACA > Google Hangouts: [email protected] <mailto:[email protected]> > Cell & SMS: 1-517-607-9370 > [email protected] <mailto:[email protected]> > > > > On Dec 4, 2015, at 2:13 PM, Adam Moffett <[email protected] > <mailto:[email protected]>> wrote: > > The DSP in the ePMP can do some kind of processing to correct for the 45 > degree offset when you have slant on one end and V+H on the other. I might > not be stating it with the correct technical jargon, but that's the gist of > it. They sell a dual slant sector for the AP with the intent to use it with > V+H integrated SM. > > This is a built in feature of the Atheros chipset, so presumably UBNT radios > can do the same thing. > > That all said...I would try to match them up as just a matter of principle. > > > > On 12/4/2015 2:07 PM, Joshaven Mailing Lists wrote: > Your AP & SM should always have the same antenna orientation. I promise you > that you don’t want slant on the AP and not on the CPE. If the signal is so > obstructed that the orientation is screwed up to the point that unmatched > polarization is actually a benefit then there is something seriously wrong… > > > Sincerely, > Joshaven Potter > MTCNA, MTCRE, MTCWE, MTCTCE, UACA > Google Hangouts: [email protected] <mailto:[email protected]> > Cell & SMS: 1-517-607-9370 > [email protected] <mailto:[email protected]> > > > > On Dec 4, 2015, at 1:59 PM, Paul McCall < > <mailto:[email protected]>[email protected] <mailto:[email protected]>> wrote: > > > We are looking at smaller sector sizes for a 5 Ghz ePMP cluster (60 degree > probably), and am considering my options, which might also increase my gain > quite a bit. Using a non-Dual Slant sector such as AM-5AC21-60, would > increase my options. There have been a calling threads on Cambium’s sites > about whether Dual Slant was a big factor at the AP if the SMs aren’t > dual-slant. > > Cambium’s Daniel Sullivan made this comment … The thread was originally > about 2.4 Ghz options, so not sure if it applies exactly to 5 Ghz. > > Paul > > > > > <ePMP_2_4_GHz Antenna_Configuration.pdf> > >
