IIRC the ePMP thing works because of the phase magic but I don't recall the specifics. Ray posted a PDF from one of the engineers explaining it but I can't find it. May be on their forum.
As far as the new slant antennas, in theory if you have a ton of both VPOL and HPOL noise, and no slant noise, then you'll get a 3db increase in SNR as the noise is effectively reduced by 3db. At least until everyone goes slant and then it's noisy as hell like the rest of it (just like how HPOL used to be soooo quiet back in the day yadda yadda). On Wed, Mar 25, 2015 at 4:23 PM, Mathew Howard <[email protected]> wrote: > I don't think that is the case with MIMO radios, so you probably actually do > gain some interference rejection then. I base this on Cambium's explanation > of how ePMP is able to use dual slant sectors with dual linear client > antennas by using phase to differentiate the two streams... of course I > might be completely misunderstanding how all of this works. > > On Wed, Mar 25, 2015 at 3:01 PM, Chuck McCown <[email protected]> wrote: >> >> The only time where one a 0 is equivalent to two at –3 is if they are >> phase coherent. Coming from the same source and phase locked with each >> other. I honestly do not know if that is the case with the Mimo Radios. >> >> From: Mathew Howard >> Sent: Wednesday, March 25, 2015 1:58 PM >> To: af >> Subject: Re: [AFMUG] AF5X polarization >> >> But in the case of dual chain radios, is what Ken said correct, that one >> signal at 0db amounts to the same thing as two at -3db? If that's the case, >> there wouldn't seem to be any interference rejection advantage to dual slant >> over dual linear, regardless of what polarity the interference is. >> >> On Wed, Mar 25, 2015 at 2:55 PM, Chuck McCown <[email protected]> wrote: >>> >>> Depends on which chuck you mean.... >>> Slant helps with multipath. Linear to slant rejection is only 3 dB. If >>> your interference is dual pol linear, you have two choices: >>> Stay linear with a different frequency and hope for the best. Or use >>> dual slant for a 3 dB reduction of the interfering signal. Better than a >>> poke in the eye with a sharp stick. >>> >>> But if you are only running one single chain/radio and the interference >>> is on the same frequency, orient your antenna 90 degrees to the interference >>> and you will get 20+ dB of rejection. Irrespective of the absolute >>> polarization. If they are +45 make yours –45 etc etc. >>> >>> From: Jeremy >>> Sent: Wednesday, March 25, 2015 1:47 PM >>> To: [email protected] >>> Subject: Re: [AFMUG] AF5X polarization >>> >>> Yeah, I knew about the multipath advantages. It seemed to me that 3db of >>> rejection would increase your CINR by 3db. Am I wrong here? Chuck? >>> >>> On Wed, Mar 25, 2015 at 1:44 PM, Mathew Howard <[email protected]> >>> wrote: >>>> >>>> I'm not sure that it really gains much if anything as far as >>>> interference rejection... I've read that even though the interfering V/H >>>> signals are going to be 3db weaker, you're now going to be seeing two >>>> signals (assuming dual polarity H/V interference) at that same signal level >>>> and the two combined is essentially the same as seeing the extra 3db. >>>> Hopefully someone who actually knows can confirm whether or not that's >>>> true. >>>> >>>> if that is the case, I think dual slant is mostly only going to help >>>> with multipath issues. >>>> >>>> On Wed, Mar 25, 2015 at 2:36 PM, Jeremy <[email protected]> wrote: >>>>> >>>>> Well if I can gain 3db by turning 45/45 I'm all over that. >>>>> >>>>> On Wed, Mar 25, 2015 at 1:32 PM, Josh Luthman >>>>> <[email protected]> wrote: >>>>>> >>>>>> That's what everyone keeps saying =) >>>>>> >>>>>> >>>>>> Josh Luthman >>>>>> Office: 937-552-2340 >>>>>> Direct: 937-552-2343 >>>>>> 1100 Wayne St >>>>>> Suite 1337 >>>>>> Troy, OH 45373 >>>>>> >>>>>> On Wed, Mar 25, 2015 at 3:30 PM, Jeremy <[email protected]> >>>>>> wrote: >>>>>>> >>>>>>> 3db right? >>>>>>> >>>>>>> On Wed, Mar 25, 2015 at 12:54 PM, Josh Luthman >>>>>>> <[email protected]> wrote: >>>>>>>> >>>>>>>> Rejection from other V/H radios. >>>>>>>> >>>>>>>> >>>>>>>> Josh Luthman >>>>>>>> Office: 937-552-2340 >>>>>>>> Direct: 937-552-2343 >>>>>>>> 1100 Wayne St >>>>>>>> Suite 1337 >>>>>>>> Troy, OH 45373 >>>>>>>> >>>>>>>> On Wed, Mar 25, 2015 at 2:53 PM, Ken Hohhof <[email protected]> wrote: >>>>>>>>> >>>>>>>>> Anybody know what you give up by using V/H instead of dual slant >>>>>>>>> with the AF5X? >>>>>>>>> >>>>>>>>> If the path has clear LOS and no multipath, I can't see why it >>>>>>>>> would care or even be able to tell the difference. >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>> >>>> >>> >>> >> >> > >
