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The audio out of the I and Q signals have a 24KHz bandwidth, but
their relationship tell the PC if the signal is above or below the
quadrature clock. Those two signals together represent a 48 KHz swath
of radio signals. Not each having 24KHz of the spectrum, but together
they have 48KHz.

The PC is able to "put" a phoney carrier anywhere in that 48KHz space
so that the signal is demodulated correctly into audio.

But whether you have a crystal that is low or one that is high, it
makes no difference as long as the signal is in the band-pass, you
still need USB and LSB demodulation. That crystal just sets the
center of the frequency range that you are looking at.

It's kind like looking at book but you have a piece of cardboard with
a rectangle cut in it, as you move that piece of cardboard you see
different parts of the book. A word may be on the right side of the
rectangle but when you move the cardboard its on the left side now,
but the letters don't reverse do they? The signals just move their
position in the frequency spectrum as you move the crystal frequency,
you still need USB and LSB decoders.

Somebody else feel free to try to explain how it works. There are
plenty of people on this list that are more knowledgeable than I am.

If you shift the desired signal up or down in freq you would need to
shift it back
to its natural audio freq spectrum


IF = 8330 kHz center of pass band

Suppose SSB signl .3 - 2 kHz

output IF filter 8330.3 - 8332 kHz depending on tuning
front end IF BW > 2 kHz

softrock board xtal 8352 kHz or 8318 kHz

output from board I and Q : 11.7 kHz - 10.0 kHz
USB -> LSB

In order to copy the I/O signal it needs to be shifted back to .3 to
2 kHz by "mixing"

My question was what is the freq. range of this "mixing" process in
the powerSDR software,.
the computer

The same case can be made for the use of a softrock crystal of 8318
kHz In that case there would be
no side band switch.

73 Rein W6/PA0ZN

KD5NWA wrote:

The radio is simplicity itself, and it receives a band of signals
that is 48KHz wide, it has only one oscillator, the rest is faked by
the computer. The radio has two signals it puts out, I and Q that
are sampled by a sound card taking samples of both channels at a rate
of 48KHz, after the computer reads those two signals it figures out
the rest in it's program.

The SR-40 has a oscillator that is used in creating a quadrature
phased clock at the center of the band that you are interested in.
This clock is used to extract the I and Q signals in the frequency
range of interest, the detectors, injection of carrier, filtering ,
etc all the typical added on hardware of a radio is handled by the
software in the PC. This makes the radio hardware very simple,
"Elegance through simplicity" as I like to say of simple designs that
do the job well.

The main Osc. is crystal controlled and divided by 4 to generate
clocks in Quadrature to "detect" the signals in the frequency range
of interest. Some of us are trying to find the appropriate crystals
so we can move the frequency of the receiver to our area of interest.
In my case I want on to be able to look at the IF frequency range of
Kenwood HF radios, that frequency is 8.830MHz, I need some crystals a
little higher or lower than 4 times that frequency (around 35.3 MHz),
not an easy task if you are not willing to spend a lot of money on the
crystal.

At 03:20 PM 9/28/2005, you wrote:
>Hi All,
>
>Question. Does Power SDR software provide a "Variable Beat or Carrier
>Oscillator"? Perhaps 2 ?
>What is the freq range of that oscillator ( up to 48 or 96 kHz ? )
>
>73 Rein W6/PA0ZN
>
>KD5NWA wrote:
>
> > It would only let me see 6.5 KHz on one side.
> >
> > I'm going to try putting two crystals in parallel, and try to pull
> > them so I can get at least 10 KHz on either side of the IF, the

> > > crystals are cheap enough. I'll get the ones that are close to the

> > center of the IF and pull them down. I'll also buy one that is
> > 68.8KHz lower than the 4X IF frequency, just in case.
> >
> > At 01:58 PM 9/28/2005, Tony Parks wrote:
> > >Cecil,
> > >
> > >The crystal that is 17 kHz low would work well if you are

meaning the

> > >crystal is 68 kHz low at its fundamental frequency. Seventeen kHz
> > low even
> > >at its fundamental frequency would still probably be ok.
> > >
> > >
> > >----- Original Message -----

Cecil Bayona
KD5NWA
www.qrpradio.com

'Never argue with an idiot. They drag you down to their level then
beat you with experience.'



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--
Cecil
KD5NWA
<www.qrpradio.com>

I fail to see why doing the same thing over and over and getting the
same results every time is insanity: I've almost proved it isn't;
only a few more tests now and I'm sure results will differ this time
...




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