[TenTec] SDR-1000

[James Duffer]

What is your take on the post which stated the SDR-1000 was to have a MDS of 
"-160?"

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 
hard/firm-ware changes.

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 
time (60s).


>From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
>Reply-To: geraldj at storm.weather.net,Discussion of Ten-Tec Equipment 
><tentec at contesting.com>
>To: Discussion of Ten-Tec Equipment <tentec at contesting.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 
>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 "discernible" 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
> >
>-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
>easier.
>
>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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