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.'
