Speaking of longer links. I see people run the same size antennas on all of their installs far too often.
I've seen 19dB panels on links that can't be less than 10 to 12 miles. I see 24dB grids on 1 mile links. Here is my rule of thumb. It'll have to change based on YOUR hardware etc. I'm always shooting for that -65 to -75 signal level, at BOTH ends of the link. up to 5 miles, 15dB up to 8 miles, 19dB over 8 miles, 24dB grid. On some of our 5 gig I have gone as high as a 3' dish for a customer on a ptmp system. He's around 15 miles from the tower and gets a steady 3/2 megs. The max that his Alvarion VL unit will allow. Pretty cool stuff. marlon ----- Original Message ----- From: "Mike" <m...@aweiowa.com> To: "WISPA General List" <wireless@wispa.org> Sent: Friday, October 16, 2009 7:23 AM Subject: Re: [WISPA] New install driving me crazy.... > Reading with interest this thread and especially Marlon's take. > > I have seen power lines in the Fresnel zone play havoc with a > signal. Especially when the wind blows. I have found the same thing > regarding placement of the radio. Many times a few feet one way or > another just works. I liken it to the black magic of radio propagation. > > The -60 signal in question CAN be too hot like Marlon intimated. His > analysis of the multi-path is probably right on. > > I don't know what your atmospherics are right now, but this is always > the dreaded time of year for me. It has been raining for the past > several days. It's colder than usual, and there has been some > ducting going on. The leaves are dead on the trees and soaking up > that moisture. > > Installs where I am using knife edge diffraction as a propagation > medium aren't as hot as they were a couple weeks ago. The hill I am > shooting over has tall grass that is all wet now. The row of trees a > mile away I'm shooting over are full of moisture and not diffracting > the signal like it was this summer. > > OK, for some of the voodoo science all this entails, here are some > basic observations I've made regarding some of these problem installs. > > Trees or power lines in the near field that move and are in the > Fresnel zone can kill throughput. The signal may look hot, but they > can drop packets like mad. > > Using knife edge diffraction, G seems to work better than B; > horizontal better than vertical. > > Sometimes off pointing an antenna slightly can attenuate a secondary > multi-path signal. > > Always leave a service loop coiled behind an install. CAT5 > stretchers are very expensive. It's much easier to make one shorter if > needed. > > I endeavor to make the signal reciprocal, or within 3dB at each > end. An alligator station will do nothing except add RF pollution. > > When doing an install, if possible, I carry a spare long CAT5 cable > and a throw away laptop. I try to find the sweet spot before I tack > anything down. > > Like I said, many times this whole thing smacks of black magic. > > I had a woman call me once from *WAY* too far away. I said, OK, I am > going to turn on the light on the tower, tell me if you see it. "I > see it," she said. Incredulous, and slightly bored, I told her I was > going to turn it off and tell me when it goes off. I waited several > seconds and turned off the light. "Ok, it's off she said." Now I > was sitting up and taking notes. I asked her to tell me when it goes > back on. She told me. I thought it was absolutely incredible that > she could see my tower from where she was. She wanted to move into > this old farmhouse, and wasn't going to do it unless she could get > Internet access. Guess what? She's one of my most vocal and > supportive customers and is almost 12 miles away. > > Mike > > At 08:44 AM 10/16/2009, Marlon wrote: >>Is that a bigger or smaller antenna size than what you have now? >> >>If you moved up by 10' and increased your signal levels, what 1000% or so, >>I'd REALLY say that this is looking like a multipath issue. >> >>Often with multipath I've seen the signals hold well but performance suck. >>It'll sometimes kill the signal though. >> >>I had one install that has some power lines in the way. Fought >>intermittent >>outages etc. for over a year. His signal was OK, but not great. Finally >>something changes a bit and his signal dropped too low. >> >>Hmmm, bad radio. So I pulled his radio out and put in a brand new one, >>still crappy signal. >> >>Double hmmmmm >> >>I put the old radio back in, left it off the mount and moved it around to >>see what would happen. (I always leave 6 to 10' of cable on the mount >>just >>for things like this.) >> >>Triple hmmmmm >> >>Move the radio to the west 6' and DOWN 2' and he's got great signal, >>faster >>speeds than ever and is happy as a clam. Now one of my biggest PITA >>customers just never calls anymore. It was a very amazing transformation >>to >>his service. >> >>Again, there were some powerlines *close* to the path but not in it. >>Things >>actually looked pretty good to me. But not to the radio. >> >>Your symptoms look like multipath to me. We don't see it's effect very >>often, the systems handle it quite well today. But when it hits it can >>hit >>hard. >> >>laters, >>marlon >> >>----- Original Message ----- >>From: "Mark McElvy" <mmce...@accubak.com> >>To: "WISPA General List" <wireless@wispa.org> >>Sent: Friday, October 16, 2009 4:50 AM >>Subject: Re: [WISPA] New install driving me crazy.... >> >> >> > Well before moving to the current setup, I originally had a CPQ-19, 10 >> > ft lower. It had a -80 with the same result and I was seeing a lot of >> > retries. >> > >> > -----Original Message----- >> > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On >> > Behalf Of Marlon K. Schafer >> > Sent: Thursday, October 15, 2009 9:30 PM >> > To: WISPA General List >> > Subject: Re: [WISPA] New install driving me crazy.... >> > >> > Change from b to g or g to be mode. >> > >> > Turn your power WAY down. That's way too hot of a signal. >> > >> > Any metal, trees, houses, power lines etc. anywhere near the signal >> > path? >> > >> > This looks a LOT like multipath. >> > marlon >> > >> > ----- Original Message ----- >> > From: "Mark McElvy" <mmce...@accubak.com> >> > To: "WISPA General List" <wireless@wispa.org> >> > Sent: Thursday, October 15, 2009 2:30 PM >> > Subject: [WISPA] New install driving me crazy.... >> > >> > >> >> Installing a new customer, Tranzeo CPQ-19 to a MT AP, -60 signal >> > up/dn, >> >> -102 noise. About half the time I don't get name resolution and can't >> >> browse pages. This happens with two different radios. It is kind of >> >> acting like I am loosing routing or something. I also notice I will >> > get >> >> very high ping times sporadically along with drop pings. Best of my >> >> knowledge no one else having issue on this AP, about a dozen users. >> >> >> >> >> >> >> >> Mark McElvy >> >> AccuBak Data Systems, Inc. >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> > ------------------------------------------------------------------------ >> > -------- >> >> WISPA Wants You! 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