On 11/20/2013 8:48 PM, Kai wrote:
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.
The entire problem with this argument is that 2200 Hz or 2800 Hz is
not what the Commission *intended* when the current regulations were
written. The *intent* of the 300 baud regulations were to keep the
occupied bandwidth consistent with other narrow band modes - e.g.,
CW and 170 Hz shift RTTY. Commission representatives at that time
even told many of us who were working on such "new" modes as HF packet
that the *intent* was to keep signals less than 1 KHz *MAX* - as was
the case with the original 850 Hz shift RTTY - and their preference
was that bandwidths be maintained at less than 500 Hz (consistent with
300 baud and 200 Hz shift packet and the original PACTOR systems which
were based on AMTOR/SITOR).
If the *intent* of this proposal is to eliminate an "outdated" symbol
rate requirement, it should have been structured with a 500 Hz target
bandwidth in mind - certainly *no more than 1 KHz* in the beginning.
Instead, this proposal serves only to promote PACTOR 5 or 6 with ever
wider signals and ever greater interference footprints from the
auto-responding systems.
If one wants greater bandwidth, at least have the decency to face the
issue *honestly* and reintroduce "regulation by bandwidth" and place
those 1 - 3 KHz wide signals in the spectrum which currently have
permitted bandwidths up to 6 KHz.
The bottom line is that 2.8 KHz signals are *not compatible* in an
area where 2 KHz can contain 16 to 18 PSK31 signals, a dozen JT65
signals, more than two dozen JT9 signals or a half-dozen traditional
RTTY signals. Between regulation and gentlemen's agreements or band
plans, most of the US HF bands have less than 30 KHz available for
narrow digital modes - and the non-traditional (WARC) bands have half
that or less. Just as the Commission has held for 60 years that it is
good policy to separate wide band (voice) modes from the narrow band
(CW/RTTY/DATA) modes, it should not take the chance that a relatively
few "high symbol rate" digital signals to might monopolize the limited
spectrum allotted by regulation for digital or expand further into the
spectrum heavily utilized for CW operation.
The Commission recognized the wisdom of protecting the many from the
few when it limited the spectrum available for automatically controlled
digital systems in the late 1980s and should again reaffirm what it has
understood for 80 years by answering the ARRL's absurd petition with
regulations that replace the "outdated" symbol rate limits with a 500
Hz bandwidth limit in the current "data" allocations.
73,
... Joe, W4TV
On 11/20/2013 8:48 PM, Kai wrote:
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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