Re: rooftop antenna range


Jeff Liebermann <jeffl@xxxxxxxxxxxxxxxxxxxxxx> writes:
Duh. I thought the name sounded familiar. I've been using your web
page on DGPS over the Internet as reference material for some of my
DGPS experiments and projects. Thanks much.

You're welcome! I'm glad my spare dgps radio went to good use. After
dragging it up many of the local mountains along with a 4.5 AH 12v
battery, I decided I needed to find a good home for it that didn't
involve me carrying large hunks of lead and sulfuric acid up and down
45-degree inclines.

You're going to have an additional problem with an omni antenna if
you're in Fremont CA. You'll get LOTS of interference from other
2.4GHz users. See:
http://wireless.wikia.com/wiki/Wi-Fi#Interference
for a list of potential interference sources. The problem with an
omni is that it picks up this junk from all directions. The more gain
the omni has, the more junk it picks up.

Hmm. I hadn't considered that.

After years without a laptop (after my last one walked out my back
door) I did finally get another one. One of the first field trips was
to drive around to two of the close by free Fremont hotspots to see
how usable they were. Simply running "iwlist wlan0 scan" in a loop as
I drove to the sites showed that there were tons of wifi transmitters
on every residential block. There were even a few hits on what I
could have sworn came from a rent-a-cop car with a ssid of
'something-or-other-security'.

My thought at the time was: this is great, look at all the folks that
might be interested in helping to form a mesh network. I see now I
was looking at it from the wrong side. All this chatter is going to
be a real problem.

However, a directional (dish) antenna only picks up junk along the
line of sight. This can still be a problem, but is much less a
problem than the junk picked up by an omni.

I might need to do that. I don't mind the cost as much as the
neighborly karma points I burn. I figured a small omni is going to
raise a lot less ire than even a wire dish pointed at what looks like
some poor person's roof.

-wolfgang
--
Wolfgang S. Rupprecht http://www.wsrcc.com/wolfgang/
.