i dont know exactly the bahavior of the electromagnatic rays transmitted by the ominiantenna in general…
so if we have an aceess point that is ominantenna 5 ghz on a tower with 25m elevation…
what is the best elevation that we should put the wireless 5ghz station device ..is it 10,15 or the same elevation(25) of the accesspoint ?
lets say that the distance between the two points is about 200m.
please need the answer…
with my good greetings..
What you have to consider is the radiation polar paterns both horizontal @360° and probally 7 to 9° vertical on a omni,
http://en.wikipedia.org/wiki/Radiation_pattern, so from horizontal axis the vertical beam will be 3.5° to 4.5° above and below horizontal axis,
What you have to consider is the radiation polar paterns both horizontal @360° and probally 7 to 9° vertical on a omni,
do you mean that the optimum situation which get the maximum signal strength is to put the wireless device(client station) in front of ominiantenna .i mean if the elevation of ominiantenna is 25m the best the signal get it will be in 25m for a station client.
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please want an idea
with thanksssss
do you mean that the optimum situation which get the maximum signal strength is to put the wireless device(client station) in front of ominiantenna .i mean if the elevation of ominiantenna is 25m the best the signal get it will be in 25m for a station client.
No - check this link and input the technical specifications of the Omni http://www.terabeam.com/support/calculations/downtilt-cover.php remember your antenna is mounted vertical, where as sector antenna’s are tilted from the vertical for maximum signal in a confined area but this does not apply to omni’s.http://www.itelite.net/en/Katalog/5-GHz-80211a-Triband//PRO-SECTOR50017VBOX.html, from the calculations link you will discover that @25meters = 82feet, inner radius is 0.2 of a mile to the horizon for max signal coverage area.
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thank you very much…reference to the image above i see two important things
1- inner/outer cell radius
2- vertical beamwidth
is the distance between the end of inner cell radius to the end of outer cell radius is the( reall cverage area )= exactly the vertical beamwidth area ??
the final question …please/
is the increasing of elevation of the omini= the increasing of vertical beamwidth area ??
again thank you very very much
i will give you a karma
greetings…
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is the distance between the end of inner cell radius to the end of outer cell radius is the( reall cverage area )= exactly the vertical beamwidth area ??
the final question …please/
At 25 meters = 82 feet the inner cell distance is 0.2 mile inside which -3db signal occurs but also the signal strength will increase as you reduce the distance from client to Omni, as radiation patterns are not exactly as quoted,
is the increasing of elevation of the omini= the increasing of vertical beamwidth area ??
No quite the opposite as the omni if mounted vertical will always have coverage +/- 4.5° (if 9° vertical) from the horizon, for example increase to 100 feet then inner cell radius is 0.24 mile, decrease to 50 feet and you have 0.12 mile to horizon,
Thank you for the Karma.
Don’t forget to mention that your have Omni antenna’s with a electronical down tilt of 3-5 degrees.
Also, the higher gain Omni, usually the narrower the vertical beam-width.
So. for relative short distance where energy doesn’t have to travel far (and thus no need for high gain antenna) you can use a low gain omni and these come sometimes with 8 to even 12º v-beam.
Also, at 200meters signal can be good enough for directional antenna client to pick up sufficiant signal even ´under´ the actual working beam of the omni.
Example, I have a 10 meter high mast 1 mtr. beside my office with on top a 5Ghz omni.
Every omni ´shoots over’ my office with its ´beam´, that is clear. But the 13dBi antenna with 17dBm radio and 10 meter of cable still has enough energy radiated downwards so I can log my laptop into this antenna with some signal level in the -70 range.
So. for relative short distance where energy doesn’t have to travel far (and thus no need for high gain antenna) you can use a low gain omni and these come sometimes with 8 to even 12º v-beam.
Also, at 200meters signal can be good enough for directional antenna client to pick up sufficiant signal even ´under´ the actual working beam of the omni.
thankss for your post
but there is something called ( the optimum or the maximum ) ..so… what is the maximum point in our image can get 100/100 of antenna’s energy let’s say where is the optimum coverage area in our example ?
You only get most of antenna’s energy if you connect omni side by side to client antenna. And still you loose signal because omni radiates 360 degrees and client now only ´catches´ some 5 degrees or so. So basically you only ´catch´ 5% of the total emitted energy by the antenna. The rest is send of in free space…
Every antenna has something what you can call a foot print. The higher the antenna, the further away its footprint on the earth. It also becomes bigger (because is is an extending circle) and thus the field strength per square meter is also less. You need to look at the antenna specs to see its working beam graph and then implement it on your situation. Also, don’t forget antenna’s have side lobs en some ´dead´ zones in-between these. It can well be that some CPE gets better signal just by moving it 10 meters further ´away´ of omni. (In close range of AP, not at distances.)
So to say what the optimum location for an CPE listening to a certain omni is: in the working beam/footprint of the antenna.
The bottom line is that the field strength of omni received by the CPE should be at the radio somewhere between -40 and -90 and have at least a SNR of 20dB.
Many factors come in place to get such signals:
- gain of omni
- gain of CPE antenna
- quality of both antenna’s.
- construction of both antenna’s (omni, sector or directional)
- Height of both antenna.s above the surrounding area.
- In case of directional CPE, the aligning of it.
- length and quality of coax used on both ends
- amount of coax connectors used at both ends.
- sensitivity of both end’s radios.
- transmit power of both end’s radios.
- distance between both antenna’s
- LOS and Fresnel zone between antenna’s
- Interference from other sources.
On the internet several tools can be found to calculate what you might expect as a signal with some data input in the math. But its not rare if the reality proofs to give different results.
very very great for this information
thank you very much
i will give you a karma
It’s been a pleasure. Thanks.