"Kristoff Bonne" wrote in message
...
Tom Holden schreef:
Just interested. Does anybody know if the AM-decoding in a "normal price"
SW-receiver is done in hardware or in software (ASIC/DSP)?

I'm not aware of any radios at any price that do AM decoding by DSP. I
suspect they exist in some form - after all, that is what one would
expect from Software Defined Radio technology. What about these new DRM
radios - do they also do AM and FM demodulation via DSP?

Well, I was more thinking in term of ASICs then "generic" DSP-processors.

Whether general-purpose DSP or ASIC DSP or software DSP running on a general
purpose CPU, it's still DSP.


When I left school (in 1993), I saw the first ASIC-chips (a V21/V23
decoder) which where based on DSP-technology; so I guess these things must
be pretty commonplace now.
If that is the case, a AM-decoder which is also able to do "detect" a
AM-signal is infact SBBc and decode it correct (and not as a "normal"
DSB-AM signal).

It's called a synchronous AM detector. While not commonplace, it is included
in several 'better' receivers. AM Stereo receivers used sync AM detectors.
The Sony IC-2010 has a highly reputed sync AM IC - analog. The WinRadio line
looks to include both sync AM and conventional envelope detectors in the
software DSP that runs on the PC to demodulate the 12 kHz IF output fed into
the PC sound system. Any sync AM detector is capable of demodulating both
DSB-AM with carrier and SSBc AM. As it is a product detector with a
synchronised BFO, the same detector may also be used for SSB suppressed
carrier and other modes, especially by defeating the synchroniser.

Concerning the DRM-chips, if you look at the specification from TI (see
link below, they say that this one chipset can do DAB, DRM, FM, RDS and AM
(plus mp2, mp3 and wma-playback).

So this does look like a SDR but I don't know if it is actually possible
to "flash" the device and upload new DSP-code into it.

The Radioscape module based on this chipset can be programmed via USB. It
looks to incorporate AM envelope detection as standard.

Regards,

Tom