That's a lot of sugar for less than a dollar Jack. I'd be willing to pay for that info! (Or buy you a round - or both)
Thanks, Mac > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Jack Unger > Sent: Friday, May 18, 2007 5:33 PM > To: WISPA General List > Subject: Re: [WISPA] 180* sector choices > > Rick, > > Here's what I see that's good about the Pac Wireless antenna: > > 1. The 3-in-1 design may be the only solution where only one > antenna-mounting space exists on a tower. > > 2. The inclusion of electrical downtilt will minimize overshooting > customers. > > 3. The inclusion of null fill will minimize connectivity problems with > customers located very close to the tower. > > 4. The 15 dBi gain is in the appropriate and usable range. > > 5. The weight (14 lbs) will make the antenna easy to raise and mount. > > 6. The price range ($700) is moderate considering that you're really > getting three sector antennas in one. > > Here's what I see that will need special consideration and planning. > > 1. The front-to-back ratio is only 15 dB. This is low compared to the 30 > dB that I usually recommend for high-quality antennas. > > 2. The sector-to-sector isolation is 35 dB. When compared to the 83 dB > of isolation that 10 feet of vertical separation would provide, 35 dB is > a lot less. > > In summary, this appears to be a good antenna system with the one > limitation that the somewhat low f/b ratio and sector-to-sector > isolation will combine to place the burden for good AP-to-AP isolation > on the quality of the co-located access point receivers and the quality > of the overall AP/site design. Receivers with poor or moderate > selectivity (in other words, receivers on Wi-Fi cards) will be > overloaded by the other AP transmitters with the result being a > throughput reduction that begins when traffic levels increase. The more > traffic, the more missed incoming packets, the more retransmissions and > the more throughput reduction. The result will be that the site reaches > saturation sooner and won't handle as much traffic as a site where the > AP receivers are not being overloaded. > > The solution (other than to use really expensive equipment which has > good receiver filtering and selectivity built in) is to again use > single-channel bandpass filters on each AP. These will reduce the level > of signal from the co-located adjacent-channel AP transmitters and > permit the site to handle more traffic (reach saturation later) than a > site where the receivers ARE being overloaded. > > Finally, in addition to the above, it's important not to "defeat" the > antenna isolation by letting RF energy "leak" directly from AP to AP > either on the ground or from PC-card to PC card. Proper shielding and > grounding will help to maintain that hard-won receiver-to-transmitter > isolation resulting in a high-performance, high-traffic handling, > reliable, profitable site. > > jack > > > Rick Harnish wrote: > > Jack, > > > > While we are on this topic, look at the .pdf file and give me your > comments > > on this all in one sector from Pac Wireless? > > > > > > Thanks, > > > > Rick Harnish > > President > > OnlyInternet Broadband & Wireless, Inc. > > 260-827-2482 > > Founding Member of WISPA > > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > > Behalf Of Jack Unger > > Sent: Friday, May 18, 2007 4:18 PM > > To: WISPA General List > > Subject: Re: [WISPA] 180* sector choices > > > > Mac, > > > > Thanks for replying to my concerns and suggestions. > > > > Have you tried using 5 to 10 feet of vertical separation between the > > antennas rather than mounting them all at the same height? 10 feet of > > vertical separation should be enough to prevent one AP transmitter from > > overloading another AP receiver. > > > > Secondly, single-channel bandpass filters are available which will > > provide additional receiver protection from nearby transmitters > > operating on non-overlapping frequencies. > > > > Finally, higher-priced antennas normally have a higher front-to-back > > ratio which increases isolation (minimizes interaction) between the > > antennas. A minimum f/b ratio of 30 dBm is recommended. > > > > Keep in mind that without dealing with these antenna isolation issues, > > you will likely have the same problems using two 180* sector antennas as > > you have had using three 120* sector antennas. > > > > jack > > > > > > Mac Dearman wrote: > >> See in line please > >> > >> > >>> Behalf of Jack Unger > >>> > >>> Mac, > >>> > >>> Before you discard the idea of using three 120* sectors are you > >>> absolutely certain that the "separation" issue is really due to the > >>> antennas not being far enough apart? Have you thoroughly looked at > other > >>> reasons why there could be interference between three APs like: > >> > >> [Mac says:] > >> > >> Well Jack - I'd like to think that I have exhausted the other > > possibilities > >> :-) but I am always willing to listen. > >> > >>> 1. Using three cards on a single motherboard in one enclosure without > >>> sufficient shielding between them. > >> > >> [Mac says:] > >> > >> All of our sector arrays utilize 3 different enclosures with one radio > to > >> the enclosure and then I try to separate the enclosures (and antennas) > as > >> far as possible. > >> > >>> 2. Using three APs that are configured on frequencies that are too > close > >>> together and are interfering with each other? > >> > >> [Mac says:] > >> > >> Unless we deploy 4 90* sectors we use non overlapping channels (1, 6 & > > 11) > >> > >>> I guess what I'm asking is (before you go spend money on antennas that > >>> may or may not solve the problem) what equipment are you currently > >>> using, how is it configured, and how far apart can you actually get > >>> three sector antennas on the 25G tower? > >>> > >>> jack > >> [Mac says:] > >> > >> > >> I have come to the conclusion that it is interference from the > backplane > > of > >> the antennas due to not having adequate separation from each other. > These > >> small towers (although 180') like Rohn 25G aren't but 12" across - so > you > >> wind up with the 3 sectors only 1' apart at their bases. > >> > >> I wish you had some more ideas :-), but thanks for the thought and the > > time! > >> Mac > >> > >> > >> > >> > >> > >> > >> > >> > > > > -- > Jack Unger ([EMAIL PROTECTED]) - President, Ask-Wi.Com, Inc. > FCC License # PG-12-25133 > Serving the Broadband Wireless Industry Since 1993 > Author of the WISP Handbook - "Deploying License-Free Wireless WANs" > True Vendor-Neutral Wireless Consulting-Training-Troubleshooting > FCC Part 15 Certification for Manufacturers and Service Providers > Phone (VoIP Over Broadband Wireless) 818-227-4220 www.ask-wi.com > > > -- > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ -- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
