Fro: Peter Laws:
> > So yes, under the proposal US stations would not be allowed to
> > transmit RTTY in the 3520-3525 KHz area or below 7030 KHz or below
> > 3580 KHz. That the rulemaking petition chose 200 Hz and not
> > 250 Hz or 300 Hz was not entirely arbitrary.
>
> So if we changed shift to 125 Hz, assuming that still allows 45.45
> Baud, we'd be able to transmit right to the bottom of the band, right?
If you are going to change shift, why not make it 45 Hz or even 22.5 Hz
(minimum shift keying) as advocated by JE3HHT? 170 Hz based on reducing
the shift from 850 (170 = 850/5) as demodulators were made better and
the rules applied pressure to get the bandwidth under 500 Hz.
170 Hz shift is about as narrow as the old filter/slicer TUs (and early
PLL designs) would operate reliably. Now, with DSP techniques MSK is a
serious possibility. 90 Hz shift would be 2x baud rate and 45 Hz would
be equal to baud rate ... both would also fit the 200 Hz criteria and
would be easy/clean with modern DSP implementations.
73,
... Joe, W4TV
_______________________________________________
RTTY mailing list
RTTY@contesting.com
http://lists.contesting.com/mailman/listinfo/rtty
|