[hpsdr] MDS

[Robert McGwier]

It is my personal design preference to have an extremely well design 
preamplifier capable of delivering whatever minimum noise figure we want 
on HF.  We then raise the noise figure to accommodate different 
antenna,  QTH, etc. noise environments with the use of attenuators.  If 
we use an excellent Output IP3 design,  we can get increased input IP3 
with these attenuators that allow the noise floor of the receive system 
to more nearly match the ambient temperature.  I see no reason to change 
my opinion at this time.

My experiences at FN20rg vary from exactly what Ulrich sees on 17 meters 
to occassionally as bad or worse than John has seen on the 10 meter 
band.  Versatility would be the key since I think it is easy enough for 
us to be versatile.

73's
Bob
N4HY


John B. Stephensen wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>   
>
> ------------------------------------------------------------------------
>
> Since the CCIR measurements were made with an omnidirectional 
> antenna,they would have to be an average. However, when I had a 
> 5-element 10 meter beam in the Los Angeles area, I never saw anything 
> below 20 dB even with the band closed. If there is a switchable RF 
> preamplifier, most conditons should be able to be accomodated.
>  
> 73,
>  
> John
> KD6OZH
>  
>
>     ----- Original Message -----
>     *From:* KA2WEU at aol.com <mailto:KA2WEU at aol.com>
>     *To:* grant at ghengineering.co.uk <mailto:grant at ghengineering.co.uk>
>     ; hpsdr at hpsdr.org <mailto:hpsdr at hpsdr.org>
>     *Sent:* Friday, August 11, 2006 15:44 UTC
>     *Subject:* Re: [hpsdr] MDS
>
>     ***** High Performance Software Defined Radio Discussion List *****
>
>     ------------------------------------------------------------------------
>     This is somewhat inconsistent with my measurements with a beam on
>     17 to 10 m. I would loook for a sensitivity of a NF of 6Dm...
>      
>     73 de Ulrich, N1UL
>      
>      
>      
>     In a message dated 11.08.2006 14:23:27 Westeuropäische Normalzeit,
>     grant at ghengineering.co.uk <mailto:grant at ghengineering.co.uk> writes:
>
>         ***** High Performance Software Defined Radio Discussion List
>         *****
>
>         John
>
>         Many thanks for posting this - I've never seen it before. 
>         Please could you
>         post the data for 160m and 6m as well if you have it, to
>         complete the list?
>
>         regards
>
>         Grant G8UBN
>
>         >Minimum atmospheric noise levels (above thermal noise) for
>         the HF bands in
>         the quietest locations at the quietest time of the year are:
>
>         >80 m  38 dB
>         >40 m  33 dB
>         >20 m  28 dB
>         >15 m  23 dB
>         >10 m  18 dB
>
>         >This is according to CCIR surveys. The receiver NF should be
>         6-10 dB lower.
>
>      
>
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-- 
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
"An expert is a man who has made all the mistakes which can be
made in a very narrow field."  Niels Bohr


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