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| Wi-Fi Range https://www.netc.com:443/bb/viewtopic.php?f=13&t=900 |
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| Author: | KingCobra [ Mon Mar 31, 2014 6:52 am ] |
| Post subject: | Re: Wi-Fi Range |
FL Panhandle wrote: Forgot to mention it (just in case you didn't already know about it).. FLAT PANEL antennas are very DIRECTIONAL. (not "omni"). Typical 14dB commonly has a 60 degree spread on the signal width... but my 24-29dB flat panel.. very narrow signal beam,, is only about 3-4 degrees wide. Any snoopers / hackers who are located OUT of my signal path,, don't even find my signals. This also is good for limiting interference from other sources. Very interesting, thanks for the share! |
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| Author: | EB94DE0D [ Wed Apr 02, 2014 3:51 pm ] |
| Post subject: | Re: Wi-Fi Range |
Congrats...you are on the right trail, when trying to "extend" the range of any RF signal. Amp's can get you there "sometimes"...whereas, the antenna route will insure you stay connected. In the ham world, we call this "more bang for the buck". And, a proper antenna doesn't need any "more" power from the mains or battery, ie: your power budget doesn't have to grow as much.. The term db is generic. But the "reference point" is "gain over isotropic" (dbi) or "gain over dipole" (dbd) to keep everyone honest when touting such gains for a price point. The nominal gain of a dipole, the most common antenna design which can "match" an output is 2.15db over/above "point source" theory or isotropic. Suffice to say: IF you build a dipole and feed it with 1w of rf power you can establish a contact x% of the time; whereas, if you feed a 3/4/5 element yagi with the same 1w of rf, your success will become x+<1%. These flat panel antennas are actuall an "array" of small antennas inside a protective cover - with some complex wiring/control systems you can actually "steer" your beam horizontally and vertically...look at the radar arrays on our navy ships now...those big flat hex shaped panels on the super structure. All of these "compact" designs work at UHF and SHF frec's - due to wavelength, like 400 MHz and on up... Hams work all the way up into the 30 and 40 Ghz bands now. At these UHF+ frec's it is true "line of sight" - most are used for point to point data links or into space itself. Very low power levels (like 100 to 400 mW) are common for our WiFi frec band..but, think of those db as a "multiplier" to your power output factor. Ie: 100mW x 10 db = EROP of 1w +/- (effective radiated output power). This "gain" is effected by the "focusing effect" of your "antenna system" (when compared to a standard, common, dipole). Think of it like your signal is distributed all around your "vertical" antenna "equally". IF you went around that circle and "took" all the signal you could from say 270 deg (3/4) of the full circle, and then "piled" it on top of that last 90 deg (1/4) of the circle -- you would end up with 4 times the orginal signal strength in that one segment (less some losses and reflected power). I can close by saying, ham's now use a hybrid system/software of "wifi" via HF frec's. We can handle data/GUI/e-mail over many 1,000's of miles between stations during disaster recovery. We also have other software using the soundcard in our PC's to enable us to communicate with 800-1,000w of RF BOUNCED OFF THE MOON AND RETURNED TO THE EARTH...we call it EME. And, yes, it takes some very high gain antennas with tracking drives! Check it out on ARRL.com ... Check-6 |
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