Doing a little Googllng (not Binging), apparently with VPOL the reflected wave is in phase with the incident wave, but for HPOL it is flipped 180 degrees out of phase.
This would lead me to believe that in a VH dual pol system, V and H would not fade out at the same time, because the fades occur when the reflected signal path is an odd multiple of half a wavelength longer than the direct path so that cancellation occurs. But in actual situations I feel like they fade together. Now for dual slant. +45 and -45 can be though of as half V and half H, but visualizing what happens upon reflection, with the HPOL component experiencing a phase flip, my feeble brain is not up to the task. I think someone explained this once, maybe even on this list, but I don’t remember the explanation. Add in the signal processing in the receiver that can recover the dual slant carriers even if the antenna is VH, and it’s way above my pay grade. I do however vaguely recall someone claiming dual slant would be more resistant to multipath fading due to reflection/refraction off atmospheric boundaries, crops, or terrain. From: AF <[email protected]> On Behalf Of [email protected] Sent: Saturday, June 29, 2024 2:22 PM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] Multipath mitigation Yeah, it had to do with buildings with all their vertical corners and edges diffracting everything. I remember reading a paper on it. Not sure if anyone ever put it to good use. FB broadcast is circular I think, so similar effects. From: Bill Prince Sent: Saturday, June 29, 2024 1:11 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] Multipath mitigation The dual slant is good for an urban environment where most of the surfaces are horizontal or vertical. Not so much in a rural environment, but a flat field comes close. -- bp part15sbs{at}gmail{dot}com On Sat, Jun 29, 2024 at 11:53 AM Ken Hohhof <[email protected] <mailto:[email protected]> > wrote: Do I remember something about dual slant polarization was supposed to help with multipath? I haven’t observed that to be the case. From: AF <[email protected] <mailto:[email protected]> > On Behalf Of [email protected] <mailto:[email protected]> Sent: Saturday, June 29, 2024 1:37 PM To: AnimalFarm Microwave Users Group <[email protected] <mailto:[email protected]> > Subject: Re: [AFMUG] Multipath mitigation Spacial or frequency diverse systems need two receivers. I don’t know of any solution that just uses one receiver. If you put up two antennas and phase them together you will just create a new pattern with higher gain in one direction and new nulls. So it will still fade. You need two SMs and a way to select the best one. Or maybe just go in and swap the connection between them remotely at the right time of year. If there was an STP that would check link quality rather than speed that could be a thing. Best Regards, Chuck McCown McCown Technology Corporation 8401 N Commerce Dr Lake Point, Utah 84074 801-250-9503 Office 435-830-4306 Cell www.mccowntech.com <http://www.mccowntech.com> www.microtrench.pro <http://www.microtrench.pro> www.terabitnetworks.com <http://www.terabitnetworks.com> From: Steve Jones Sent: Saturday, June 29, 2024 11:09 AM To: AnimalFarm Microwave Users Group Subject: [AFMUG] Multipath mitigation Is there an SM side solution for this? We have a handful of customers we have to go out twice a year to move their equipment up 5 feet or down 5 feet. In the fall, I love to point out they just harvested the field across the road, didnt they. theyre always "how did you know" I could take the loss hit in many of these cases to do a splitter and diverse antennas, but would that harm or hurt more? Some of them we just have 2 radios installed a spring and fall radio, we just have them swap which ones plugged in. 2 450b SMs leaves a lot of budget for something that doesnt require touching One of you geeks has to have come up with a solution over the years other than truck rolls. _____ -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com _____ -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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