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Re: LF: Probably not a new question...

To: <[email protected]>
Subject: Re: LF: Probably not a new question...
From: "Graham" <[email protected]>
Date: Wed, 28 Apr 2010 00:39:43 +0100
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One  thing to  watch is the  military radios are  sometimes not  100 % compatible  with ham operation  , which oddly  can be  more demanding in term's  of filtering , dynamic range , and  add on's  like noise suppression and  post audio  processing , I have  three commercial  radios , skanti  R5003 - suffers  from cross  mode  from the  local MW tx  .. supposed to  be used at  sea ..  RA6790GM which has one of most  mechanical AGC systems ever  and is is very  noisy to the  point of fatiguing  with  headphones .. but  can be set to  1 Hz and the  bfo  is  synth as  well in 100  hz steps , RA1778  handles nicely .. but  has a  1.4 meg vfo  for the  bfo .. ssb is  phase locked  , so  cannot  use the  narrow filter's  for  data ...and  so  it  go's  on ... the MA1723  exciter  took a  second MA1723  to  get it  going .... etc
 
.to be honest  for  most thing's the  ft897-d , with its  add  on dsp   works fine ....!
G .

Sent: Tuesday, April 27, 2010 3:02 PM
Subject: Re: LF: Probably not a new question...

OK, now I see the concept much clearer than I knew before (with my apologies for having stressed the subject a bit :-)).
All this stuff is very interesting and promising, with very high perfomance/cost ratio and great scalability. I think I will be seriously evaluating to homebrew a good SDR project in the coming months (the only choice I can afford from a financial point of view :-))
Cheers
D.
----- Original Message -----
Sent: Tuesday, April 27, 2010 3:13 PM
Subject: Re: LF: Probably not a new question...

On 4/27/2010 2:25 AM, Daniele Tincani wrote:
Hi Alberto,
 
I'm quite familiar with digital signal processing (I work in the embedded SW area for a big manufacturer of telecommunications equipments and digital streams of several Gbit/s are common on our boards), nevertheless I know that analog conditioning of signals (before they become "numbers") is at least as important as the digital treatment, unless you accept to sample meaningless information (noise) at the ADC :-) Anyway I'm sure this is dealt with perfectly in SDR's so I think we can stop here this discussion.
Thank you for clarifications.
Cheers
D,
Hi Daniele,

   I wasn't specifically addressing you in my past message, I was just trying to explain what is behind some diffidence that often it is possible to hear or to read
about the SDR technology.  And the Softrocks are a mixed blessing... from one side they helped a lot with their very low cost the diffusion of the SDR concepts
among the ham community. But on the opposite side, their lackluster performance generated in some the impression that SDR is a technology still much behind
its classical analog counterpart, which isn't....

You are perfectly right when saying that the analog portion in front of the digitizer is of utmost importance, to not have to deal with meaningless numbers.
That's why the tendency is to bring the digitization stage as close as possible to the antenna... and, at least for the HF bands, this goal is almost reached with
the QuickSilver and the Perseus SDR....

73  Alberto  I2PHD



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