Re: [TenTec] SDR-1000

["James Duffer" <dufferjames@hotmail.com>]

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@storm.weather.net>
> Reply-To: geraldj@storm.weather.net,Discussion of Ten-Tec Equipment 
> <tentec@contesting.com>
> To: Discussion of Ten-Tec Equipment <tentec@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
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec