> Humm? Those DF9IC modems I know of use FSK (well the modem is actually
> a PAM modem, the transceiver converts that to FSK)
You're right, it is FSK, but you could also describe it as a signal
with a phase shift of 0 or +pi/2 after each 0-transition
and a shift of -pi/2 or 0 after each peak.
Somebody once told me that 4-dpsk was the more correct term, and I've
never thought about it since, so I'm not sure what to say... any
clues welcome :)
> On the contrary, these modems aren't very bandwidth-efficient,
> if I recall correctly they use about 1.2 times the bandwidth
> of a WA4DSY modem.
Yes, but they use less than the common AFSK and manchester modems.
Who would expect them to perform as well as the MSK modems which
rely on a linear channel? If you have that there is such a lot you
can do...
> And besides, there's now a 200kHz duplex (i.e. 2 times 200kHz)
> channel allocated on 70cm for 76.8kbit/s user access. This was
> demonstrated last weekend at the Friedrichshafen fair.
Cool... where are they located? I still think it would be a shame to
use them for manchester, though. 38.4 in 250kHz just isn't what I'm
dreaming of. :)
Kai