[Lf] What is the best RX for 136 kHz?]

[Andre' Kesteloot]

Alberto di Bene wrote:

> Klaus von der Heide wrote:
>
> >
> > What is the best RX for 136 kHz?
> >
> > That depends on what you personally mean by "best"
> > (cheapest, most versatile, best IP, frequency stability ...)
> >
> > My personal goal is to be able to adapt to any situation.
> > >From this point of view the "best" receiver is the following:
> >
> > After an input filter a low-noise operational amplifier
> > is followed by an analog to digital converter. The receiver
> > structure, the demodulation, noise blanking etc... is entirely
> > programmed on a DSP or on one of the new Million-Gates FPGAs.
> >
> > 73 de Klaus, DJ5HG
> >
>
> I substantially agree, with a precisation :
> depending on the type of demodulation you wish to do on the signal,
> having the I and Q components is of great help. So, why not mix down
> the 137 kHz signal to baseband, using a couple of mixers fed with
> an oscillator that produce two signals in quadrature ? Some DDS have
> this capability, so the +- 90 degrees shifting could also be done
> digitally, reducing the analog part of the receiver to the bare minimum.
> Then the two I and Q components could be fed to the left and right
> inputs of a stereo sound card, and all the processing done on a Pentium,
> which nowadays rivals in processing speed with DSPs that only a few years
> ago were considered state of the art.
> Just food for thought...
>
> Alberto    I2PHD