--- In [email protected], "trgkrazytrev" <[EMAIL PROTECTED]>
wrote:
> How do you get your front end tuned into recieve and desired
> frequency, is there an oscillator circuit needed or can your simple
> use a signal generator or something along them lines to allow the
> mixer to select the apropriate signal
>
> Any help at all would be greatly appreciated
> Thanks
> Trev
Trev-
I believe you are using one of the QSD (quadrature sampling detector)
designs shown in the files section. These receiver designs are
essentially mixers that mix the incoming signal down to a very low IF
suitable for feeding into a soundcard on a PC.
So to receive a signal at say 30 MHz you need to supply an LO near 30
MHz such that the difference between your desired receive signal's
frequency and the local oscillator's frequency is about 15 kHz. The
QSD detectors require an LO that is 4X the receive frequency since the
oscillator signal gets divided by 4 to develop the required quadrature
signal to drive the mixer. In this case the LO would be approx. 120
MHz.
You _can_ utilize a plain mixer to create a low frewquency IF to be
fed to the SDRadio but the benefits of IQ conversion in the front end
of the SDRadio will be lost. Utilizing this mode of operation your LO
would be at 30 MHz as opposed to 120 MHz.
-Ray WB6TPU
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/soft_radio/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
