What is your take on the post which stated the SDR-1000 was to have a MDS of
My two main HF radios, an Omni VI, and a FT-1000D have, I believe a decent
MDS, but it still seems that ambient noise is the limiting factor. I don't
think a MDS of -160 would resullt in a beneficial improvement.
As I recall from the post, the -160 was being predicted with some future
73, Jim de wd4air
P.S. That radar site had a microwave system manufactured by Collins radio.
I also use to work at a microwave repeater site located in Thalman, GA which
was frequency and space diversity using Collins equipment. I just haven't
heard many people mention the fact that Collins was big in microwave at one
>From: "Dr. Gerald N. Johnson" <email@example.com>
>Reply-To: firstname.lastname@example.org,Discussion of Ten-Tec Equipment
>To: Discussion of Ten-Tec Equipment <email@example.com>
>Subject: Re: [TenTec] SDR-1000
>Date: Fri, 14 Jul 2006 20:22:08 -0500
>On Fri, 2006-07-14 at 06:47 -0500, James Duffer wrote:
> > I was under the impression that noise was partially caused by
> > (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
> > near Memphis TN. Also a MDS of -114 dBm was considered an excellent
> > and this was using a parametric preamplifier. And the "discernible" in
> > 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"
> > had something broke!. I am not referring to man made noise.
> > 73, Jim wd4air
>-114 DBM is a pretty good MDS for radar bandwidth. For CW bandwidth, MDS
>of -148 dBm is pretty good. Noise power goes with the square of
>bandwidth. Noise is generated by random electron motion. Its a current
>so the voltage developed depends on the resistor value and the resistor
>temperature. It is possible to create a preamp that has no intentional
>resistors so that the noise is significantly less than a resistor at
>room temperature. e.g. a noise figure of a quarter dB or a noise
>temperature of 20 or 30 degrees K. That is like the noise from a
>resistor 20 or 30 Degrees C above absolute zero and its not quite
>necessary for the preamp to be cooled way down though that makes it
>When the radar receiver gets good enough to see sun noise, its hearing
>lots of man made noise too.
>73, Jerry, K0CQ,
>All content copyright Dr. Gerald N. Johnson, electrical engineer
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