FrankC29

I'm out in the boons. We have three locations each about a mile apart from eachother. If you connected the three locations on paper, you would have a perfect triangle. One location is a home where I plan on installing Direcway satellite internet service. The other 2 locations are offices at our dairy and calf ranch. Perfect LOS between all locations, nothing in the way at all. My idea is to create a network here that would share the satellite broadband service between all locations, which would in turn allow me to setup surveillance cameras at all locations that I could monitor from home, and by having the satellite service installed at home, I would also get a lower rate from Direcway. From all the scrounging I've done on the net, the way I think up is to have an omnidirectional antenna at the house location and then yagi-type antennas at the office location? Does this sound right? Would this kind of setup be able to travel 1 mile reliably? Any suggestions most welcome! Thanks.

Dutch

Have you done the math ? Calculated your linkbudget ? Calculated the Fresnel zone ?
If not, go forth and do so..

(Hint: If the above technical terms doesn't mean anything to you, then use this to learn more.. )

Dutch

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totbenru

Using typical 2.4ghz AP specs (transmit power 15dBm, receive sensitivity -80dBm for 11mbs & -65dBm for 54mbps) and the planning calc from (http://www.swisswireless.org/wlan_calc_en.html) you can predict the throughput of ur network using common yagi and parabolic antennas.
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If we target 11mbps of throughput with a:

Antenna - 12dBi yagi for remote site & 15dBi omni for base station
Target throughput AP receive sensitivity for 11mbps - (-80dBm)
Free space loss for 1mile (1.6kms) - (-104.48dB)
Cable losses (assuming ur gonna use 50ft or more runs of lmr240) - (-6dB more or less for 2 stations)
AP transmit power - 15dBm (32mw)

Then u have a margin of 11dB (see screenshot).

This means that ur received signal level will always stay above ur targeted -80dBm; giving u a stable throughput... in theory. In reality, interference, weather, badly pointed antenna ect. will dictate that u shud have at least a 15dB fade margin. (whatever equipment u use, keep above this margin)
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Now lets use a 19dBi parabolic antenna for remote sites and the same 15dBi omni for base:

(same data to compute)

You now will have a 18dB fade margin. Stable enough for 11mbps.
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Now we try a target throughput of 54mbps. Your receive signal shud be -65dBm.

19dBi antenna for remote site 15dBi omni for base
(same path loss, cable losses & AP transmit)

You only have a 3dB margin (see screenshot). Your throughput will fluctuate but will still work well at lower speeds.
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Same as above (54mbps target) but with a 24dBi Parabolic antenna for remote site:

Only 8dBm of margin. Still not enough for a solid 54mbps throughput but certainly stable link (for most network aps e.g. internet, lan gaming ect.).

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You can also use 2 parabolic antennas for your base station. One pointed to each station (assuming you have 2 antenna inputs). You can also use bi-amps. They start at 100mw (20dBm) and go as high as 2 watts (33dBm). In the end, its the cost/benifit ratio that will dictate ur setup. But before pumping up the juice, be sure of the legal limits in your state. And also, the most important, check your propagation path. You can create a lot of interference even with a small AP if plugged into a 30dBi antenna .



'Hope this helps.

Attached Images

	11mbps_15dbm_12dbi_15dbi.jpg (18.3 KB, 30 views)
	54mbps_15dbm_19dbi_15dbi.jpg (18.2 KB, 16 views)

wrzwaldo

And also assuming they are not setup as diversity antennas. Or you can turn off diversity and still use both antennas (not likely).

Also note that if you are in the US and want this in the unlicensed bands you will need to adhere to the FCC power limits. There are different limits for P-to-P (Point to Point) and P-to-MP (Point to MultiPoint).

FrankC29

Thank you. While much of the preceeding went way over my head like a flock of seagulls, I at least now now that it is feasible with off the shelf equipment. I am willing to spend soime money on this project up to a reasonable amount ($500 give or take). I am also thinking it may be simpler just to cut out one location and have two directional antennas facing directly towards eachother. This makes it a slam dunk with a couple of yagis in the 14-15 dB range, correct? Well, I'll research this anyway. Thanks again.

wrzwaldo

If you have RF LOS then it should be a fairly easy setup. I wouldn't call it a slam dunk (expect / calculate for the worse).

Airstreamer

Yup. But you know what seagulls do when they fly over...
Murphys' law strikes again!

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