Because yagi antenna concentrates the forward radiation and response. -Lucy :)
On Sun, Oct 18, 2009 at 9:48 PM, Mike <[email protected]> wrote: > Rick: > > Why did it solve the problem? Better side lobe attenuation? 'Splain Lucy. > > Mike > > At 08:42 PM 10/18/2009, you wrote: >>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 >><[email protected]> 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" <[email protected]> >> > To: "WISPA General List" <[email protected]> >> > 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: [email protected] [mailto:[email protected]] 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" <[email protected]> >> >> To: "WISPA General List" <[email protected]> >> >> 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: [email protected] [mailto:[email protected]] 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" <[email protected]> >> >>> To: "WISPA General List" <[email protected]> >> >>> 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: [email protected] >> >>>> >> >>>> Subscribe/Unsubscribe: >> >>>> http://lists.wispa.org/mailman/listinfo/wireless >> >>>> >> >>>> Archives: http://lists.wispa.org/pipermail/wireless/ >> >>> >> >>> >> >>> >> >>> ------------------------------------------------------------------------ >> >>> -------- >> >>> WISPA Wants You! 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