I was under the impression that noise was partially caused by temperature
(molecular activity). I know that the sun causes noise, as I used to
observe the sun strobe on the FAA long range radar I maintained for years
near Memphis TN. Also a MDS of -114 dBm was considered an excellent figure
and this was using a parametric preamplifier. And the "discernable" in MDS
was by observing the pulse just as it came out of the noise. There was
always noise, every day of the year. Believe me if there was no "grass" you
had something broke!. I am not referring to man made noise.
73, Jim wd4air
>From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
>Reply-To: geraldj@storm.weather.net,Discussion of Ten-Tec Equipment
><tentec@contesting.com>
>To: tentec@contesting.com
>Subject: Re: [TenTec] SDR-1000
>Date: Thu, 13 Jul 2006 21:30:58 -0500
>
>On Wed, 2006-07-12 at 21:06 -0500, James Duffer wrote:
> > Is this -160 dbm? What is the level of ambient noise?
> > Would it be less than 1 micromicromicromicro watts.
> > The point is what good is having a sensitivity that would allow
> > detection of signals that are below the noise floor????
> >
> > Jim de wd4air
> >
>The noise floor is not a stable signal level, nor uniform over the
>world. There are quiet locations and quiet times, some predictable, and
>some not. Then there may be some signal processing techniques to copy
>signals that to the ear are weaker than the noise. A few of us can do
>that by ear, so it can be handy to have reduced the noise contribution
>of thee receiver so its not the limit, so that external noise is always
>the limit and there's still room for ear or computer processing to copy
>signals 20 or more dB below the noise level. To those ears, a signal at
>MDS is nearly S-9.
>
>--
>73, Jerry, K0CQ,
>All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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