[Lf] Re: LF Remote Receiver

[Vittorio De Tomasi]

Hi Frank,

Frank Gentges wrote:
> 
> Vittorio,
> 
> Your numbers look attractive.  The filter seems to be growing here to 2
> chips and 54 1% resistors.   If we can do it in the processor for free
> that may be a key advantage.  

Since you want to throw away chips and resistors and use dsp, may I
suggest you to throw away also your RX320 receiver ?!?

 I'm not joking: put together a tight band pass filter at 137 kHz, a
SBL-1 mixer, a local oscillator somewhere around 130 kHz, a post
amplifier, and extract from this an i.f. frequency at 7 kHz, so that we
can detect radio signals directly with a sound card and a dsp software
implementing a ssb detector!

By the way, Spectran will work as a poor man's substitute for a dsp
receiver: simply zoom on the i.f. region, and you will see what you are
receiving.

With the 16 bit of resolution available from a sound card, we get about
96 dB of dynamic range for this "receiver", not bad but probably not
enough. However 24 bit sound card are becoming available (also if they
are not cheap), and this is around 140 dB of dynamic range...

There is no need for a pll/dss conversion oscillator, since tuning can
be easily done in dsp (at least within a certain frequency range).

Anything else to throw away ?!?

vy 73

Vittorio

-- 
*************************************************************************
Vittorio De Tomasi         ik2czl at amsat.org
Home page:                 http://space.tin.it/scienza/vdetomas 
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"Wir muessen wissen; wir werden wissen" (David Hilbert)