> --- In [email protected], "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> wrote:
>
>> Alberto:
>>
>> I never did ask anyone about the offset clock frequency to the
>>
> quad mixers you suggest for use with the Winrad software? Is it 12
> kHz such as the Soft Rock 40 suggest or 96 KHz in this case? It sort
> of came up in a discussion at soft rock group. I am ready to try a
> vfo design on my SR 40 v6 and want to know what I am getting into.
>
>> ka9rza
>>
>
> Well, there are two different ways of using an SDR program. One is
> like Flex does, choosing a fixed last IF, 11.025 Hz in their case
> (neglecting for a moment the anti-spur trick), and commanding the HW
> LO accordingly. Then the final conversion to zero IF is done in the
> software, together with demodulation.
>
> Another way is to have a wide last IF, as wide as the sampling
> frequency permits, e.g. from -48 to +48 kHz with 96 kHz sampling, and
> then tune inside this chunk the wanted signal, using a point-and-click
> technique in the software. Then the HW LO will need to jump in
> discrete steps of 96 kHz (or a bit less, to have some overlap). You
> see on the screen the entire chunk, the individual CW or SSB QSOs, and
> you choose which one you want to listen to. My personal preferences go
> to this way, and SDRadio and Winrad have been designed with this kind
> of utilization in mind.
>
>
This is how PowerSDR works for the "soft rock" mode and it is how it
will work for all receivers (especially the watch receivers and the
adjacent channel interference mitigation receivers) in the new version
of things. I have delusions of grandeur about killing off to inaudible
adjacent channel interference that leaks into your band by using a watch
receiver tuned to the main power of the interferer and producing a
cancellation signal from that for the energy that falls in your passband.
Bob
> However nobody prevents you from using the first method with SDRadio,
> choosing whatever last IF frequency pleases you most. Just stay a bit
> away from the zero spot, to avoid the well known problems. 11025 Hz is
> a good choice as any other. And if you are intending to build a VFO,
> not a synthesizer, you are almost obliged to use the first method, as
> it would be a bit difficult to tune a VFO in discrete, all equal, steps.
>
> 73 Alberto I2PHD
>
>
>
>
>
--
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
Laziness is the number one inspiration for ingenuity. Guilty as charged!
YAHOO! GROUPS LINKS
- Visit your group "soft_radio" on the web.
- To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
- Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
