Yes, or building a simple "SoftRock style" direct conversion front end
and feed the audio to the soundcard for further processing by Winrad or
similar software capable of processing I/Q audio. What you need is some
kind of preselection filer, a quadrature mixer (half-complex mixer,
"Tayloe mixer") and a pair of good audio preamps. The front end LO can
be as simple as an XTAL oscillator followed by a 74HC74 that divides the
XTAL frequency by 4 and produces the two 0/90 degree clocks needed by
the mixer. A 74HC4052 analog switch works quite well as mixer on LF,
this one can be clocked by the 'HC74 mentioned above or any other 2-bit
synchronous binary counter clocked by fLO*4. The tuning is done in the
software.
You can find some ideas at
http://yu1lm.qrpradio.com
or look at Gerald Youngblood's QEX article series "A Software Defined
Radio for the masses"
http://www.flex-radio.com/News.aspx?topic=publications
73 de Johan SM6LKM
Graham skrev 2010-04-26 20:55:
> You may be better building a LF convertor ?
>
> G ..
>
> *From:* Daniele Tincani <mailto:[email protected]>
> *Sent:* Monday, April 26, 2010 6:23 PM
> *To:* [email protected] <mailto:[email protected]>
> *Subject:* LF: Probably not a new question...
>
> Hi LF,
> among the so-called "communications receivers" (0.1-30MHz, all modes,
> well-known brands, etc.) in the "< 300 euros" price range (used, of
> course :-)), which models have good characteristics at LF frequencies?
> Any recommended models (in the same price range) outside of the "comms
> receivers" class?
> Many thanks for your feedbacks.
> Cheers
> D.
>
>
>
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