Txpower calibration

G.W. Haywood ged
Fri Feb 3 06:28:21 PST 2006

Hi Jim,

On Fri, 3 Feb 2006, Jim Thompson wrote:

> and there are a number of factors here which are likely far more
> responsible for the 6dB swing than anything you indicate.  These
> are, primarily:

> 1) There is likely a lot more "activity" in 2.4GHz during the day than
> during the night.  (People do eventually go to bed.)

Do they gradually ramp up their transmitted power over an hour or so?
Do they only work on sunny days in August?  It's a great pity that you
didn't see that graph.  I'll send you a copy privately.  Unfortunately

Received: from [x.x.x.x] (rrcs-x-x-x-x.west.biz.rr.com [x.x.x.x])
        by netgate.com (Postfix) with ESMTP id E6F7C280016;

you're using a provider that I routinely block at our firewalls for the
obvious reasons, so you won't be able to see it over HTTP.

> 2) The noise floor increases during the day both due to #1 above, and
> the simple fact that as the earth and atmosphere warm, the thermal noise
> seen by the receiver must also increase!

Well, er, I _did_ talk about temperature.  :)  However the noise power is
going to be approximately proportional to the temperature above absolute
zero so the difference in noise between 283K (10C) and 308K (35C) is only
about nine percent - hardly sufficient to explain a factor of more than
four difference in the sognal strength.  BTW I should have mentioned that
the signal strength is lower when it's warm.  I'm unable to measure SNR on
this particular setup because there appears to be a firmware problem in
the version of station firmware (1.5.6) in the Netgear MA311 card.

Well, this is really OT so let's continue it privately if you want to -
always eager to hear experience from other people.


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