Wireless over 10+ miles (Mr. Bandel?)

Thu Oct 12 10:51:30 PDT 2006

On 10/12/06, Bruce Marshall <bmarsh at bmarsh.com> wrote:
> On Thursday 12 October 2006 10:52, Matthew Carpenter wrote:
> > Hello all,
> >
> > With my recent change of jobs, I have higher demand for fast Internet
> > speeds. I live in the boonies so DSL and Cable are not an option (ok, so
> > the n00b CAble salesman thinks they can get me hooked up on 10/18, but
> > let's be real) at&t just rejected my T1 purchase order (after making me
> > wait a month for the estimate).  I'd like to consider paying someone else
> > for their broadband, and using point-to-point wireless to bring me the last
> > few miles.
> >
> > My initial plans are two of the following:
> > * WRT-54GL running OpenWRT (the full-featured Linux codebase)
> > * High-gain Yagi antenna set on a 30-ft antenna tower (get over
> > trees/stuff)
> >
> > (David in particular)
> > Would you recommend using the above setup (I already have the routers), or
> > do you recommend some other hardware to handle the wireless portion?
> >
> > This is going to happen relatively soon, so any input would be valued.
> >
> > Thanks,
> > Matt
>
> I too live in the boonies and found that there was a wireless setup about a
> MILE away.   Figured it would be a snap to use it since I have a 110 foot ham
> tower (but I do live down a hill which takes away about 90 feet of that.
>
> I put up their flat-plate style antenna which is what they normally use.
> Nope, it worked but was really a low signal.   I went and bought a yagi (I'd
> have to look up the db gain but it was the best I could find)  and that
> improved the signal to a 'mid-level' signal and even that is marginal.
>
> So 10 miles??  I don't think it will hack it.   The power levels used are
> pretty low, and you'd have to point the antenna very accurately in any case.
>
> Lots of luck....   (sorry)

You're a HAM radio operator and saying this? <sigh>

I have _no_ experience with the WRT setup, but this is more commodity gear.

What I use (and I have a 22 mile shot on 1 W, others on 4W even longer
distance) is a WRAP board (WRAP 2c) with Atheros miniPCI a/b/g cards.
Using 5.7/5.8GHz, you can run 4 W max output legally.

The secret to long distance comms is:
1.  _good_ line of sight (no fresnel zone encroachment)
see:  http://www.pananix.com/cgi-bin/rfcalcs.pl for a good calculator
2.  proper antenna (for a 10 mi shot, even a small antenna with
moderate gain, 14-17db, will work, but buy at least a 22db grid)
3.  alignment within the 3db zone (on a 22db grid, that's a 12 degree arc)

I suggest using this radio:
http://www.netgate.com/product_info.php?products_id=158&osCsid=aeb9d3cb74fdf15eef0025d153353270
and installing StarOS (http://www.staros.com)
this antenna:
http://www.hyperlinktech.com/web/58ghz_ism_unii_grid_antenna_22dbi.php
you'll need a LMR-400 or LMR-240 cable w/ N-male ends (1 meter should
be long enough)
lightning arrestor: http://www.hyperlinktech.com/web/al6-nmnfb.php
good outdoor ethernet cable (put protection on both ends, the most
fragile part of the entire installation is the ethernet port).

You should get 12Mb _throughtput_ easily.  10Mb ethernet gives about
4Mb throughput, so that should be a guide

Values to use in my calculator:
distance:  10 mi.
frequency: 5800 MHz (==5.8GHz)
tx power both sites: 15db
antenna gain: 22db both sites
rx sens:  -95 both sites
cable loss: 1db (.25db for lightning arrestor, .25 for each connector,
.25 for cable)

20db SNR is _great_ signal.  Most of my shots have only about 12-15
max, some less.  If your noise floor rises above about -92, I'd try
another freq.

I just know what works for me.  But, unless you have all pygmy trees,
30 foot won't get you over the trees.  The antennas must "see" each
other directly.

FYI, 10 mi over "flat" terrain requires 50 towers each end due to
earth curvature (and that's with no trees in the way).  Also note that
while RF curves somewhat, it curves differently than your sight, but
not significantly.