Jose Da Silva wrote:
> I guess an AGC isn't needed if you are dealing with 100% on carrier and
> 100% off, but I thought the topic at this point included regenerative
> receivers, in which case, it might be a good idea to still have a
> signal present, say 20%, 100%  ?    now, you need an AGC.

Not really.  You still have two levels coming out of the AM detector, and
you still only need to find a threshold to distinguish between the two.
Note that there is no such thing a 0 carrier to an AM receiver.  There is
always ambient noise that will be detected as some level.  So whether the
0/1 levels are 1V and 3V coming out of the AM detector or 2V and 3V makes no
difference.

> quad opamp, FSK, clipped and filtered signal, sent to ordinary 6811
> input pin, approx 10kbit too... ...designed in 1991 ;-)
> opamp circuitry, less than $1, substitute a cheap pic for 1200baud,
> $1+$1 approx $2
>
> dsp solution starts at above $4
> http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=8071&mid=14&lang=en&pageId=75
>
> I win!  ;-)

Actually the previous version of this device cost about $125 to produce and
my new design about $82.  Part of why the DSP solution is a good idea has to
do with other things going on, but I'm not going to go into that.  My point
was only that it's possible to do this digitally, and that in some
circumstances it's a good idea to do it digitally.  In my case the dsPIC is
doing other things too and is therefore very cost effective, the solution
overall takes less board space too.  The dsPIC in its data slicer role alone
replaced 4 quad opamp packages and their surrounding analog parts, probably
about 2 square inches of board space not counting the extra 7V analog supply
that is no longer needed.  Anyway, I saw the smiley, so I think you actually
understand.


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