Hi Chen
While I personally agree with you about much lower BW in a clean-slate world,
consider the following. If the ARRL had chosen 2200 Hz instead of 2800 Hz,
their proposal would have affected absolutely nobody. The current 2200 Hz users
would continue to do their 2200 Hz thing in PACTOR (2K20J2D ITU-R/FCC
designator) or whatever. The ONLY immediate change would be that the regulations
themselves would have drastically simplified language, by removing arcane 1980's
baud-rate language. That's a good thing.
There are plenty of things that could/would/should/might and had-ought-to-be
improved in ham regs, as others have pointed out. But this proposal, and this
debate, is very simple and very limited. It would remove the baud-rate
definitions and just define digital in terms of a max BW. So max BW is really
what's under debate. If you want to take away the current privileges we all
have, and ask hams to give up all of their PACTOR modes (their lowest mode looks
like RTTY with a 740 Hz shift), than choose 500 Hz or some number near that
(which would also wipe-out RTTY for shifts above 425 Hz). If you want things to
stay pretty much as they are today, and let the PACTOR guys do their thing as
they are today, then ask for a 2200 Hz. The ARRL opted for 2800 because that
number is already in the regs for permitted digi-modes in the 60 m band
channels. It keeps the regs simple. Note that 2800 Hz may be out of reach for
the vast majority of today's HF ham transceivers - typical TX BW is usually less
than 2600 Hz. Check the TX BW specs on your rig! (Not you Chen, I know that you
use a very modern, very flexible SDR radio that can handle the wider BW on TX
and RX).
I think that it's really simple, there is nothing hidden or nefarious that I can
see, or that anyone has specifically point out. If push came to shove, I'd opt
for a 2200 Hz limit because 2200 keeps the status quo - and that could win over
the proposed ARRL number. No one gains, no one loses, we all win with simplified
regs and we all win with potentially efficient future digital modesthat could
operate in reduced BWs, say around 4-500 Hz, unhampered by today's needless
artificial baud-rate restrictions that predate modern computers.
Cheers and 73
Kai, KE4PT
On 11/20/2013 6:32 PM, Kok Chen wrote:
On Nov 20, 2013, at 3:01 PM, Kai wrote:
I think that discussion should center around what the BW limit [should] be for
digital signals. The answer will likely be something between 2200 Hz and 2800
Hz, because signals as wide as 2200 Hz are already permitted. It's good to
discuss this.
For conversational (keyboard, human-to-human) digital modes, 300 Hz to 500 Hz
is ample, and wide enough to use statistical detection methods that take
advantage of the frequency diversity aspects of selective fading on the HF
bands.
300 Hz is also sufficient to do weak signal experiments to your heart's content.
The only reason anything wider is needed is to transmit massive amounts of
"data" or digital voice.
Unless there is some enforceable rule that controls mutual interference between
conversational mode users and data mode users, the proposed change by the ARRL
only opens all of us to even worse QRM. Even a 1 kHz signal in the midst of an
RTTY contest or pileup can completely ruin it. That is what is so wrong with
the ARRL proposal.
73
Chen, W7AY
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