Vertical radiation pattern. Read this for a better description: http://www.odessaoffice.com/wireless/antenna/how_to_pick_the_right_antenna.htm
Look closely at the very first antenna pattern. http://www.odessaoffice.com/wireless/antenna/15_omni.jpg See how much of the energy goes UP instead of down. And if you look closely you'll see that the main lobe goes up instead of straight out, or, more importantly, down toward the customers. I buy the 8 dB Maxrad omni antennas with electrical downtilt these days. Almost always 4* of downtilt, but sometimes I'll go as high as 12*. If you drop from a 15 dB to a 12 you'll DOUBLE your vertical coverage zone. Or very close to it. That 15 dB omni you have probably has a 2 to 5* vertical pattern. An 8 dB will have closer to 12 or 15 (I don't remember exact numbers off the top of my head). In a nutshell, gain comes only from the focusing of energy. You can only get that in two plains. Horizontal and vertical. Everyone looks at two numbers, horizontal (omni, 120*, 180*, 90* sector etc.) and gain (15dB, 12dB, 6dB, 24dB etc.). For the customer side the horizontal pattern doesn't mean much because you'll point the antenna straight at the tower's antenna anyway. At the tower though, you need to cover MUCH more area, both from side to side AND up and down. That help? marlon ----- Original Message ----- From: "RickG" <[email protected]> To: "WISPA General List" <[email protected]> Sent: Sunday, February 22, 2009 9:23 PM Subject: Re: [WISPA] tower issue > Marlon, > > I was thinking about what you said about high gain omni antennas sending > more signal UP. With respect to direction, what's the difference between > between a high gain unit and a lower gain unit? > > -RickG > > On Sun, Feb 22, 2009 at 10:34 PM, Marlon K. Schafer > <[email protected]>wrote: > >> Not sure if it's related or not, but high gain omni antennas are usually >> a >> great big no no. They tend to send more signal UP than in the direction >> of >> the customers. >> >> I'd replace it with an 8 or 9 db unit just on principal. You'll probably >> find that most customers will actually get a BETTER signal. >> >> laters, >> marlon >> >> ----- Original Message ----- >> From: "RickG" <[email protected]> >> To: "WISPA General List" <[email protected]> >> Sent: Sunday, February 22, 2009 7:23 PM >> Subject: [WISPA] tower issue >> >> >> > OK, here a good one! (aka, how I spent my weekend in a blizzard!) >> > >> > One of my towers has a single WARP/StarOS connected to a 5GHz grid for >> > backhaul and a 15dBi omni for the local connections. >> > On Saturday, after making some small changes, I rebooted it and it >> > would >> > not >> > allow me to connect via wireless any longer - or my customers :( >> > So, I go to the tower, connect up via ethernet and everything is a >> > usual >> > but >> > I see all associations but only a few client have ip addresses. I can >> ping >> > the few clients but the packet loss is huge 80-90%. I then reload my >> > backup >> > but still get the same thing. I try changing channels, but still the >> same. >> > I >> > then systematically begin replacing parts starting with the radio card. >> > Eventually, I replaced EVERYTHING but still have the problem. One note: >> > occasionally, twice of maybe three times, after a reboot, all came back >> > normal. The third time, I left well enough alone for now but of course, >> > you >> > know what will happen the next time I reboot. >> > >> > Any ideas??? >> > >> > -RickG >> > >> > >> > >> -------------------------------------------------------------------------------- >> > WISPA Wants You! 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