On Nov 27, 2013, at 10:33 AM, Kai wrote:
> Can you/we now craft an argument that increasing that limit from the defacto
> 2200 Hz is harmful to current users?
Only through probabilistic arguments, Kai. I.e., if you are currently getting
QRM n% of the time, then expanding to 2.8 kHz would make that 1.27*n %.
*Plus,* the 2.8 kHz signal will use more power (constant power/Hertz, though --
but affects my direct sampling SDR's blocking dynamic range, nevertheless HI
HI).
The reverse happens too. If a 2.2 kHz Pactor III station is QRMed by a PSK31
station n% of the time, if they expand to 2.8 kHz, they too will get the same
ratio of extra QRM from PSK31 stations.
To be fair, its is not a complete linear relationship as that -- so I should
temper it with something weaselly like "in the worst case," when I monitored, I
see more narrower band stuff than 2.2 kHz Pactor.
I.e., if 1500 Hz stations remain at 1500 Hz, and only 2.2 kHz stations shift to
a 2.8 kHz signal, the increase in QRM probability would be a little lower.
It could just be because of my location. Other parts of the country might have
more Pactor III activity than Winmor activity. One Winmor station around here
appears to be active almost constantly, while the Pactor stations I hear which
manage to shift all the way up to SL6 seem more seldom. I have wideband (96
kHz) SDR captures if anyone is interested -- but you'll need a Macintosh
computer to play it back :-).
The real solution, IMHO, is to separate the Data and RTTY users.
We only have gentlemen's agreements currently, and that isn't working as well
as it should (not enough gentlemen? :-). If RTTY and Data were separate by
enforceable FCC rules, where Data has its own band segments (say, use the
current 97.221 "automatic station" parts of the spectrum) and keyboard RTTY has
its own band segments, and never shall the Twains meet on the spectrum, then
Data could be expanded to 6 kHz for all that most people care, and
human-to-human communications can very happily use 1500 Hz.
One can only dream...
73
Chen, W7AY
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