Russell McMahon wrote:

> More detail would help.

  As always.  From my understanding:

> - Is this by telephone (???) or radio or ???

  Telephone.  Paying STD rates which are now limited to $3.00 between
19:00 and 00:00 local.  Yes, it *is* cheaper to use the radio, but
apparently some of these enthusiasts are actually not Amateurs!

> - Describe how the overall system works.

  Key and sounder each end.

> - Knowing WHY this is done would be interesting.

  *Not* a useful question to ask a Morse fanatic!

> - The 7910 "worldchip" modem IC may still be available ([possibly
> surplus) allowing roll yer own still.

  It is a "legacy" part mostly available ready assembled inside 1200
baud modems.  The assertion (which I find curious but...) is that these
are becoming hard to find second hand.  I would have thought they were
rife and to be had for nothing.  I collect them occasionally at garage
sales, usually for a dollar or two (albeit, may have to buy the whole
computer!).

> - There are other modem IC's that would handle the data rate.
> Depending on how this all works it may be possible to make a very
> cheap and simple modem adequate to the task using a single tone
> decoder IC eg LM567!!! or a 4046 PLL IC or XR... or ....

  The users are nervous about hacking telecom stuff, legality, type
approval and all that.  Besides, that involves *work*!

> I am puzzled as to why a modem is needed at all unless there is some
> arcane extra feature that you have not mentioned.  If you use an audio
> circuit then the USER is the modem received with Morse.

  Dead right.  The "arcane extra feature" happens to be the use of
sounders for *real* Morse.  Many of these sites are historic locations
such as Timbertown at Wauchope NSW (near here).  Now it makes sense,
doesn't it?

> If you are using eg a multipoint digital data network it may make
> sense.

  Not so easy to set up using telephone lines (as requires multiple
lines).  I have proposed that using a contemporary modem and a
pre-processor (e.g. PIC = On toPIC) to send a stream of ASCII events
marked with a local clock would allow 100% faithful reproduction albeit
with a delay (maybe 1 second or so), like Speak Freely etc.

  Long breaks would allow easy re-synchronisation (a "reset" event)
This would be readily adaptable to Internet networking and "nets" etc.
with simple hardware.

  But they (being by definition, backward-looking) say they want
backward-compatibility with the present un-framed system which as I have
pointed out, just isn't "on"!
--
  Cheers,
        Paul B.