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[Ham-80211] Providing Long-range Wifi

Chriswlan2 chriswlan2 at linnixislands.com
Mon Aug 27 19:20:49 UTC 2012


My 2cts:

1-Splitting off a minor fraction of the effort on a "secondary" leg option
would tremendously increase the success rate, while lowering frustrations:
have the 24dB portable site fitted with another antenna to "shoot back" down
a great LOS second link into the target, when it is shaded out by
obstructions on the 90ft tower first link. Many times whenever a direct link
has any doubt with it before starting out, it will be much faster, as well
as more sffective, to drive straight to an intermediary clear location, and
do a 2 leg relay that have great LOSs.

2-I did a 3 mile link with good result, with 20dB panels, although there was
an obstructing hill perhaps 1/3 1/4 the way on the path. But it was a smooth
hill top and "only" perhaps 15ft "too high". Obstructions that are toward
the middle of the path are definately less trouble; important to keep in
mind.

3-I have several links across a flat treed atoll, around 7 miles: clean
"beach to beach" LOS across the lagoon, just grazing the mid point sea
level,  with panels on a single piece of pipe, is quite strong, but trying
to get "inland" from there is extremely tricky. Doing a WDS relay from an
existing nearby "beach" station is so much more effective. With lots of
luck, hours of GPS work, and walking on roof with a test panel, I once
succeeded in feeding internet directly to a "cafe", accross the lagoon and
then on through the ending half a mile of intermittent coconut plantation;
but in this special instance there was definately a somewhat vague but
helpful notch in the tree line, as seen from the Internet cafe roof.

4-In 3 above, getting UP into the notch, getting a taller pole was helpful;
but "laterally" was quite pointy.  But usually I spend a few hours with a
probing portable telescopic pole, mapping signal strength, to find the spot,
usually only a few feet in diameter, with the strongest (and hopefully
stable in varying wind directions) signal, and in my atoll situation,
"getting higher", mostly never works. Instead if I have only a very short
distance of coconut trees to go through, at the end of the path, I end up
with a panel at 8 to 15ft ONLY, to go over small brush and small buildings,
and UNDER the coconut crowns. Works fine if I can see through the TRUNKS.
Only a few (moving) coconut fronds, close in, play hell with my links.

5-Ubiquiti 2.4 radios have the option of setting channels 2 MHz off, "in
between", but in busy area probably wouldn't help. But another very
effective step in keeping non-Hams out.

6-Ubiquity affordable radios are really flexible: with the export f/w, one
can choose all kinds of freq above and below the 2.4 "wifi". (don't have US
ham allocations in mind...). The "Bullet High Power, screws direct on to the
panel N jack.

YMMV

Cheers

Christian
WO1V



Ralph wrote:
> We may have "priority", but in reality it is just on paper.
> Getting the users already there to shut down or move would pretty
> much be impossible.
> You should look at another band besides 2.4
>
> Ralph N4NEQ
>
> -----Original Message-----
> From: ham-80211-bounces at tapr.org [mailto:ham-80211-bounces at tapr.org]
> On Behalf Of Robert Dixon
> Sent: Monday, August 27, 2012 11:23 AM
> To: ham-80211 at tapr.org
> Subject: [Ham-80211] Providing Long-range Wifi
>
> I am working with our local EMA to be able to provide wifi internet
> access at disaster scenes and special events in our county.  I have
> read articles where people have achieved long distances over line of
> sight paths. But in our case, line of sight may not always be
> possible, due to rolling terrain, trees, buildings etc.  I have a 29
> db gain dish on my tower at 90 feet. The idea is to aim it at the
> required location, and use a portable gain antenna at the other end
> (maybe 24 db at 40 feet) for a point-to-point link, and then relaunch
> wifi locally for on-the scene laptops etc.  We plan to experiment
> with this as soon as we have the necessary equipment on hand.
>
> The thought is to use wifi channel 1 or 2, as that is where hams are
> priority users in the frequency allocations.  We would like to use as
> much power as possible, but the cost of commercial units may limit
> that to a watt or so.  25 miles would be adequate.
>
> Also wondering how hams typically send their callsign ID for wifi
> applications.
>
> Suggestions and comments would be most welcome.
>
> Bob W8ERD
> Delaware County, Ohio
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>
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