Point - to - Point link project Rural Internet

[Long Dx]

Hi;
I am just starting a point-to-point link in a rural farm situation for 802.11ac specifications.

Experimentation ! Any helpful suggestions appreciated.
Desire high speed high bandwidth and am using an RT-AC66u (802.11ac @1300 Mbits/sec) with a pair of discarded, free, small (solid)satellite dishes (~ 26" dia.). I was Not interested in the commercial low-throughput repeaters limited from 150 to 300Mbits/sec.

We had Bell Sympatico WiMax internet with a wireless modem, but Bell cut off 12,000 local rural customers in March 2012 and asked us to fork over to Cell Phone Internet rates at 3X to 4X the cost. Declined that.

Long Dx Internet is now working with the Asus RT-AC66u, but could be better. Am now trying to optimize the WiFi link from the cable internet (at end of driveway) to house, ~ 1200 feet away. Project cost so far ~ $290.

Hoping to improve things (Suggestions ?? )
a) Suggestions for (free)test software to benchmark & report results ?
b) Optimization of the parabolic reflector/mechanical, since signal strength is an obvious factor (~ -65 dBm right now, but fluctuates for various reasons).
c) Changes to the Asus firmware( currently 220 version) &/or Asus Admin parameters. Wondering, for instance, if I should fix the BW from 20/40MHz to 20MHz only, etc. I do not know if other Asus Admin parameters might be worthy of testing ?
d) At the other end, currently using a LinkSys AE3000 USB dongle at focus of the 2nd parabolic satellite dish { waiting for the Asus RT-AC53 USB dongle }.

Set up:
At one end of the link: the RT-AC66u is sitting, inside a plastic paint bucket bolted to the dish, up 30' in the air. Two CAT-6 cables & power go up to the router. One hassle is that the RT-AC66u small MIMO antennas flop about during installation. Am making a jig to fix these parallel/straight up, so that they don't fall over ! (I doubt that the beam steering/phasing is of any use in this point-to-point, line-of-sight application).
-- Can I turn-off beam steering without incurring loss of power or throughput ?

I have played with power levels, but not certain what the RT-AC66u is capable of.
InSIDDer shows a fair amount of bouncing around of signal strength in the 5GHz band(several channels wide). Again, any way to reduce power spread and limit losses would appear sensible.

Will likely place a 2' cylindrical-extension at the edge of @dish to further limit beam angle. I had tried a galvanized steel garbage can, with the router inside and this worked almost as well(a bit poorer) as the parabaloid; the dish mounts provided better pointing ability. Likely more gain from parabaloid than from garbage can, but, well, anyway !

Also thinking of gluing heat sinks on the Tx chips inside the Asus RT-AC66u, if this might help things. Any other hardware/firmware mods anyone know about ?

Will keep you posted, if any rural long distance WiFi folks are interested !

rick
Long Dx

 

[stevech]

no heatsinks needed. The vendors' firmware limits the real transmitter power to a max that's limited by the transmitted signal quality (Rho) so that the signal isn't distorted. That would cause errors at the receiver, even with strong signals.

There's simple math to do to calculate how far the link will go, given the transmitter power (real, not that displayed in a phony GUI like DD-WRT), coax loss if any, and antenna gain on TX and RX ends, and receiver sensitivity. The latter varies greatly by what your goal data rate is.

A parabolic dish focuses energy much like a parabolic mirror for light/sunlight. Adding stuff to the edges won't work. The beamwidth out a few meters (in the so called far field) is governed by the dish diameter, for some frequency like 2.4 or 5.8GHz.

Point to point are better done with yagi antennas than parabolics. A yagi inside a PVC radome is the best. Such as
http://www.l-com.com/familylist.aspx?id=2149

when the yagi or parabolic antenna gain gets beyond 15dBi ( a large-ish dish can be 22dBi), the beamwidth is so narrow that it is difficult to aim both antennas and keep them aimed.

So often, you see 10-15dBi antennas built into an enclosure that also houses the WiFi router. The thing is powered via the cat5 cable. This integral antenna method for bridges (like the $75 Engenious and the like), eliminates the losses from a coax from router to antenna. This coax can be a deal buster. you need 1/2 or 3/4 in. diameter coax for more than a foot or so of length, and one doesn't go more than 20' or so with LMR-400 low loss coax at 2.4GHz, much less 5.8GHz.

So point to point links with line of sight are relatively easy to design, starting with the simple math from a path loss prediction tool or the basic formulas. And aiming those high-gain antennas, and not letting the wind mis-align them. Avoiding coax losses- big deal. Integral-antenna devices are by far the best.

 

[thiggins]

Why aren't you using three antennas?

 

[DaveMcLain]

Here's a thread on this forum from a while ago and in it I had a post where I put some pictures showing a link that get's used every day (using right this second). It's at my folks' place where our business is also located and a single internet connection is shared between our shop and their house, works great using cheap gear.

http://forums.smallnetbuilder.com/showthread.php?t=3052

Since these pictures were taken the setup has changed in that the internet connection now comes to the house and the network is extended out to the shop. The equipment I've been using to make this happen for the last year or so is mostly all stuff bought off of E-Bay etc. Router and wireless AP in the house is a stock Linksys WRT610N V2(refurb), it has the stock antennas and everything. Out on the shop end is a Netgear WGR614V8 running DD-WRT firmware so that it can be configured as a "client bridge". It's also been modified to allow it to attach to the external dish antenna. This was done using a connector from an old WRT54G and about 1 minute of solder work. It's inside of the sealed box.

Inside the shop is a Linksys WRT320N that functions strictly as a switch and wireless AP to feed clients inside of the shop area, several PC's.

This setup works great and is very reliable despite having the high gain antenna at only one end. That dish is so big more is not needed on the main AP end of the link.