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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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