On Thu, 7 Oct 1999, Thomas Sailer wrote:
> My HT's start to cut off very sharply at aroudn 2.4kHz, that's where
> the maximum of the HAPN spectrum is.
Ok, then probably the fact that I had a bit more difficulty
transmitting than receiving wasn't entirely due to my weak signal
after all :^)
> also the HAPN modulation
> does not include known training bits for an equalizer
Yes, it's really time for some "modern" packet radio modulation that
uses dsp. Point-to-point links should use training sequences and
select a modulation and pre-distortion that makes optimum use of the
bandwidth for a given S/N. They could retrain once in a while to adapt
to changing weather conditions or persisting qrm.
This would also work for uplinks, provided they use some organized access
protocol, like dama. That way, the modulation characteristics of the
station sending next would be known in advance, so the master station
could use the correct decoder and parameters. A station attempting to
join the channel could use a very slow default modulation and then
be prompted for a training sequence by the master. The master's signal
could also contain clock information to make re-synchronization for
each individual transmission unnecessary.
(Even mobile stations that have access to exact position information
could remain in sync by computing the correct delay. Varying
reflections might be a problem, though, so they would have to use
Has anything like this been tried yet? I think it would be very
interesting indeed.
Kai
