On Tue, 17 Dec 2013 22:40:14 -0800, miso wrote:

First things first. I'm guessing your WISP picked channel 10 and you can't
change that. Is that the case?

Yes.
http://farm8.staticflickr.com/7299/1...48f3922e_o.jpg

A waterfall is just time dependent sniffing. If your WISP wasn't spraying
you with wifi on channel 10 (again, my guess), you would examine the
waterfall display and find the area with the least activity. Now the
waterfall is useful if someone burps wifi at you, as in a telemetry
application. If the band was crowded, you would pick the channel with the
occasional belch of wifi rather than one that is busy all the time. [If
you were doing SIGINT, you would look for patterns in the occasional wifi
belch. This is knows as traffic analysis.]

It's rare to see time on the Y axis, so I see how it's time-dependent
sniffing. I guess it also looks like a waterfall, since it's columnar
but in layers. Blue seems to be where I'd want to be, if I wasn't
constrained to be on channel 10, which is my access point channel.

My next guess is you WISP provider has a customer on channel 2 at the same
location that feeds you. [It could be another WISP from a different
vendor.] The WISP provider has a beam antennas at the transmitter site.
One beam for you on channel 10, another beam for somebody else on channel
2.

You are correct. The same WISP is feeding two different neighborhoods with
two antennas, both at the same mast, one on channel 2 and the other on
channel 10.

I can now see the waterfall is yellow'er on those two channels, as are the
power levels bluer, and the real-time view greener.

That person may live near you since you are seeing the signal, but
there are no red blobs in the waterfall, so the antenna isn't pointed
directly at you. [And why would it be?] Red means a strong signal. The
WISP on channel 2 is only 7 db less than your signal, but channel 2 and
channel 10 have no common frequencies, so nothing to worry about.

You figured out a lot from that waterfall graph that I hadn't mentioned
(because I didn't realize it might be relevant). Yes, the WISP is on both
channel 2 and 10, and both antennas are on the same tower; but only one
(channel 10) is meant for me to connect to.

You have two neighbors on channel 3, so that would be a bad channel for
you, as would any channel that overlaps channel 3. Probably the WISP
installer already knew that from when the site survey was done.

The point is duly noted to stay away from channel 3.
h
I'm not really sure how they determine the noise floor. At any one time,
there is somebody on a wifi channel. It might be really low RF level, but
not zero. Probably the receiver makes a determination that if it can't
sniff a signal, it must be noise. Not a good assumption.

I think anything the antenna sees which is not a connection signal,
is considered noise.

At -50dBm over 3 miles, I'd call it a day and go looking for something
else to fix.

You have a point that the -50dBm isn't bad for a distance of 3 miles.
I was more worried about the -88dBm of noise, but, now, after looking
further, I think that the noise level is just about at the receiver
sensitivity of -90dBm ± 2dB.

The main figure that worries me is the instantaneous noise of -40dBm.
Do you know what effect this instantaneous noise might have on the radio?