I fixed a nasty multipath issue for one of my subs by using a yagi. Here are some good sources for info: http://www.wi-fiplanet.com/tutorials/article.php/1121691 www.crystalcomltd.com/...whitepapers/124102032509Berkeley_Multipath.pdf http://www.rfengineer.net/1171/rf-basics-multipath/ http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008019f646.shtml -RickG
On Sun, Oct 18, 2009 at 10:51 AM, Marlon K. Schafer <o...@odessaoffice.com> wrote: > I don't Steve. > > But think of it like an echo. You get that first, clear signal coming in, > laser straight. Then at some point shortly after that you start getting the > reflections. If there are too many of them, and/or they are at the wrong > time the radio will get confused. > > G SHOULD handle this better than B. It's made to use multipath's echoes to > reassemble a complete message. Sometimes it works that way, sometimes it > doesn't. > > I'd have to say, for me, g is usually better with multipath than b though. > B handles interference better. At least that's what I'm seeing. I have a > tower that was giving 1 meg down 2 to 3 up, almost all customers saw that or > worse. Swapped back to b mode only and it's now a consistent 4 megs both > ways. > > Another thing to try is to turn down the power. Probably on both ends. If > you are at -69 see if you can drop your ap by 5 then 5 more db. Make sure > to drop the cpe by the same amount. What you are trying to do is move the > echo down so far that it can't be "heard". > > I've also had installs that are happiest about 2' above the ground! > > Here's a fun one for you. I've got one customer that shoots near a grain > elevator. Most of the year he works fine, but near harvest, every year, his > performance goes out the window. It seems that the wheat in the elevator is > moved out and the empty elevator is worse than the full one. > > Out here we have VERY long links. I have one at 18 miles. PTMP. Yet there > are also customers within 1 mile. 10 to 15 mile links are common place. > Multipath is a real head ache as the ground conditions change. Customer's > service will be perfect, until it snows. Or until they harvest a field, or > the ground dries out, or it rains etc. > > Fortunately MOST of the time this isn't an issue. But when it does hit ya, > it can be very hard to figure out. > > One other thing you might want to try with your customer, turn the radio to > the wrong polarity. You are very close to the tower so you should still > have enough signal. I've not had to do this very often, but it's a little > trick that has worked before. I've also pointed them 180* the wrong way and > had that work very well, especially with a grid. > > Let us know if anything helps. > marlon > > ----- Original Message ----- > From: "Steve Barnes" <st...@pcswin.com> > To: "WISPA General List" <wireless@wispa.org> > Sent: Friday, October 16, 2009 7:07 AM > Subject: Re: [WISPA] New install driving me crazy.... > > >> Marlon, DO you have or know of a good white paper on Multipath issues? I >> agree with your assessment but I have several locations that I have not >> been able to resolve Multipath for. I had an installation last week 3 >> miles from tower AP. Clear line of site other than going over the >> Neighbors Metal barn and between 4 metal grain bins. We could get a -69 On >> 50% of the property but retries were 98% No matter where we tried High-Low >> left right. 100 yards either way on the road and <10% retries and a -65 >> signal. I just need to some documentation to solidify my understanding. >> >> Steve Barnes >> Manager >> PCS-WIN >> RC-WiFi Wireless Internet Service >> >> Character cannot be developed in ease and quiet. Only through experience >> of trial and suffering can the soul be strengthened, vision cleared, >> ambition inspired, and success achieved. >> - Helen Keller >> >> -----Original Message----- >> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On >> Behalf Of Marlon K. Schafer >> Sent: Friday, October 16, 2009 9:45 AM >> To: WISPA General List >> Subject: Re: [WISPA] New install driving me crazy.... >> >> 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! Join today! >>>> http://signup.wispa.org/ >>>> >>> ------------------------------------------------------------------------ >>> -------- >>>> >>>> WISPA Wireless List: wireless@wispa.org >>>> >>>> Subscribe/Unsubscribe: >>>> http://lists.wispa.org/mailman/listinfo/wireless >>>> >>>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >>> >>> >>> ------------------------------------------------------------------------ >>> -------- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> ------------------------------------------------------------------------ >>> -------- >>> >>> WISPA Wireless List: wireless@wispa.org >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >>> >>> -------------------------------------------------------------------------------- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> -------------------------------------------------------------------------------- >>> >>> WISPA Wireless List: wireless@wispa.org >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >> >> >> >> -------------------------------------------------------------------------------- >> WISPA Wants You! Join today! >> http://signup.wispa.org/ >> -------------------------------------------------------------------------------- >> >> WISPA Wireless List: wireless@wispa.org >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ >> >> >> -------------------------------------------------------------------------------- >> WISPA Wants You! Join today! >> http://signup.wispa.org/ >> -------------------------------------------------------------------------------- >> >> WISPA Wireless List: wireless@wispa.org >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ > > > > -------------------------------------------------------------------------------- > WISPA Wants You! 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