Internet Talk Internet Talk    FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  confusion about wlan antennas          Internet Talk Forum Index -> Wireless View previous topic :: View next topic   Author Message tg Guest Posted: Tue Jul 08, 2008 11:06 am    Post subject: confusion about wlan antennas I've been messing about with my wireless card and I was using a 6db omni antenna mounted outside the house (size-wise it's like half a broomstick). My Windows XP PC showed 6 AP's in 'View Available Wireless Networks' , I got a couple of strong signals and the rest were weak. For comparison I then took down this antenna and put up a 15db omni antenna (bigger - 1.6meters long) in its place. What puzzles me is the 15db antenna picked up 12 AP's - which is double the previous antenna - but the signal of all AP's found was weak, not as strong as when using the 6dB. Is this normal behaviour for high gain antennas? What factors might cause this? poor wiring maybe? For the 15db antenna I use RG213 cable with N-connectors and for the 6db one I used ordinary TV coax with TNC. Cable length for both antennas is about 10 meters. Thanks for any pointers. Back to top   Ads Advertising Sponsor mlrodrig@gmail.com Guest Posted: Sat Jul 12, 2008 11:19 pm    Post subject: Re: confusion about wlan antennas On Jul 8, 7:07 am, "tg" <t...@nospamevereverever.net> wrote: Quote: I've been messing about with my wireless card and I was using a 6db omni antenna mounted outside the house (size-wise it's like half a broomstick). My Windows XP PC showed 6 AP's in 'View Available Wireless Networks' , I got a couple of strong signals and the rest were weak. For comparison I then took down this antenna and put up a 15db omni antenna (bigger - 1.6meters long) in its place. What puzzles me is the 15db antenna picked up 12 AP's - which is double the previous antenna - but the signal of all AP's found was weak, not as strong as when using the 6dB. Is this normal behaviour for high gain antennas? What factors might cause this? poor wiring maybe? For the 15db antenna I use RG213 cable with N-connectors and for the 6db one I used ordinary TV coax with TNC. Cable length for both antennas is about 10 meters. Thanks for any pointers. My theory is: It is all related to the meaning of "antenna gain". Why is it that one is said to have 6dB and the other 15dB? Think for a second... antennas does not have power plugs, so they don´t add power... how one can have more "energy" than the other? Here lies is the answer for your question. What an antenna with bigger gain does is concentrate the signal in a smaller area (or volume if you will, as it is 3D), so the area that is serviced get more signal (sacrificing other areas that will bet weaker signal). The same happens with reception, the bigger the gain, the smaller is the region it will do a good "listening". So an omni 15dB antenna only gets good signal from APs antennas that are on the same height as it. If the origin AP is slighter higher or lower (can be as little as few metters) it will get a weak signal. Your 15dB can hear far, but your neighbors APs (the first 6 ones) are not so well aligned with it, so the signal gets weaker. Back to top   Ads Advertising Sponsor Keith Guest Posted: Fri Jul 18, 2008 5:14 pm    Post subject: Re: confusion about wlan antennas tg wrote: Quote: I've been messing about with my wireless card and I was using a 6db omni antenna mounted outside the house (size-wise it's like half a broomstick). My Windows XP PC showed 6 AP's in 'View Available Wireless Networks' , I got a couple of strong signals and the rest were weak. For comparison I then took down this antenna and put up a 15db omni antenna (bigger - 1.6meters long) in its place. What puzzles me is the 15db antenna picked up 12 AP's - which is double the previous antenna - but the signal of all AP's found was weak, not as strong as when using the 6dB. Is this normal behaviour for high gain antennas? What factors might cause this? poor wiring maybe? For the 15db antenna I use RG213 cable with N-connectors and for the 6db one I used ordinary TV coax with TNC. Cable length for both antennas is about 10 meters. Thanks for any pointers. I am not an RF guru, but a little reading around suggests to me that a) you should definitely be using a 50 ohm coax like RG58 or your RG213 rather than standard 75 ohm TV drop cable, which has high frequency losses which are just way too high, and b) those cable runs are long - you can get signal attenuation well over 1 dB/meter at 2.4GHz, even with RG58 (I don't know about RG213, but it's probably a little better). I think the rule of thumb is to put the router as close to the antenna as possible, then run CAT5 from the router to where you need it. Compare these two articles, for instance: 1. http://en.wikipedia.org/wiki/RG-59 2. http://en.wikipedia.org/wiki/RG58 Back to top   Ads Advertising Sponsor Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         Internet Talk Forum Index -> Wireless All times are GMT Page 1 of 1   Jump to: Select a forum Internet Talk----------------Internet TalkWireless  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Australian Debt Consolidation Experts medical insurance Wedding Website Annunci di escort, accompagnatrici e massaggiatrici Free Porn Travel Cheap Car Insurance Make Your Own Website Cheap phone calls to Pakistan Cleaning Service toxic mold UK Swingers Genuine Contacts Site floor machines Vacuum Cleaner Parts 117 Attacks blocked Powered by phpBB © 2001, 2005 phpBB Group