Cecil,
I just had a look at the powerSDR-SR40 code. Looking at sdr.c line, I
can see that the signal is indeed at 11025 Hz. The RX oscillator runs
at -11025 hz. Now, does that mean, the spectrum we can indeed tune to
is centered around 7056-11.025 = 7044.9 khz? I am a bit confused here.
On 9/29/05, KD5NWA <KD5NWA@...> wrote:
The SoftRock itself doesn't convert all input signal to 11,250Hz, it
has a fixed crystal oscillator, were the signal ends up depends where
in the pass-band the original signal is. Some will be at 1KHz some at
5KHz, some at 19KHz depends on how far they are from the center of
the pass-band (7.056MHz). A QRP signal a 7.040 will end up at 16KHz.
On the SDR1000 it's another story, they have a agile oscillator so
they try to keep the signal you are tuned to at 11KHz away from the
crud at at 0Hz.
At 11:26 AM 9/29/2005, you wrote:
--- In softrock40@..., w keith griffith <kgriffit@w...>
wrote:
I have,,, 'SomeWhere' a really good description of the Weaver ssb
method.
There's a decent description of the Weaver method in the DSP section
of all the recent ARRL Handbooks.
How, if at all, does that method compare with the
softrock?
The SoftRock itself does no demodulation. All it does is sample the
incoming signal in such a way as to mix down to 11250Hz. The
downconverted signal is then dumped to the computer's soundcard.
In the subsequent software DSP on the digitized signal, the SSB
"demodulation" consists entirely of a bandpass filtering stage and
another mixing stage to spin the signal centered at 11025Hz down to
0Hz.
CW is the same, except the mixing stage spins the signal down to the
CW offset frequency (700Hz or whatever) rather than 0Hz.
73
Frank
AB2KT
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Cecil Bayona
KD5NWA
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73 - Ramakrishnan, VU3RDD
Ramakrishnan Muthukrishnan