On 7/27/2013 9:31 PM, Jeff Blaine wrote:
If I ready it right, I think that Joes original point was that this
could turn into a step which would allow an easier path for
commercial or unregulated use of the bands.
Make that *further* commercial encroachment. The maritime interests
are already using the bands illegally but pushing the bandwidth to
2.8 KHz and increasing data rat to 56K or better will make the bands
more interesting to a larger variety of users.
With encrypted protocols and no "listen before transmit" safeguards,
the autobots will run wild.
73,
... Joe, W4TV
On 7/27/2013 9:31 PM, Jeff Blaine wrote:
If I ready it right, I think that Joes original point was that this
could turn into a step which would allow an easier path for commercial
or unregulated use of the bands. While bandwidth vs. mode as tech
progresses, in the ham community the commercial encroachment is the
bigger worry - and that all makes perfect sense to me. Guys will try to
get away whatever they can and if it looks like the FCC is taking a step
back from a tight overwatch, it will be exploited.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message----- From: Kai
Sent: Thursday, July 25, 2013 4:07 PM
To: Kok Chen ; RTTY
Subject: Re: [RTTY] ARRL issues Official Reply: Re 2.8KHz HF digital BW
Hi Chen
The Henning Harmuth story was really interesting. I've run into his
works during
my tenure with Ultra Wideband and IEEE802 standards work. And folks
worry here
about 2.8 kHz BW signals! Thanks for the nice recollections.
We must remember that when radio started it was all wide band (spark)
and was
called "wireless". Eventually spark was abolished, and wireless became
narrow
band and was called "radio". Then came Armstrong who challenged "the
narrowband
mantra" to give us the audio quality of wide band FM. Later, Qualcomm
introduced
wide band digital spread spectrum, challenging the narrow band mantra
once more.
Well, we have wide band (up to 40 MHz BW) CDMA now (in dedicated bands),
and
"radio" has again become "wireless"!
Henning was right: wide and narrow don't mix very well, but remember
that 2.8
kHz ain't really wide! Many already legally do around 2 kHz digital at
HF with
currently authorized emissions (Pactor, Amtor) at HF. The proposal just
ups that
to 2.8, and more importantly, gets rid of the baud rate limitations.
My CW will always get through, and we'll always have 170shift 45.45 baud
ham-RTTY.
Thanks again, and 73
Kai, KE4PT
On 7/25/2013 4:20 PM, Kok Chen wrote:
Does this comfort you?
As comforting to a CW op feels when I unleash 2.8 kHz wide digital
signals down at 14.025 MHz, where I am authorized by the FCC to do.
Wide signals and narrow signals just don't mix (I still remember a
quote by Henning Harmuth at an IEEE conference back in the 1970s
regarding the use of Walsh Functions as radio carriers).
Keep 2.8 kHz signals above 14.125 MHz and it might make sense.
Otherwise change the existing symbol rate rules to limit bandwidth to
500 Hz. Not 2.8 kHz.
Re: Harmuth. Henning Harmuth had back in the 1960s proposed a
different orthogonal basis instead of sine waves, and had developed an
entire system (including how to phase antennas for Walsh carriers).
His orthogonal basis? The Walsh Function. And instead of Fourier
Transforms and spectrum, you have Hadamard Transforms and Hadamard
spectrum.
At one conference, someone pointedly asked (I paraphrase): "Prof.
Harmuth, your system would just splatter all over our spectrum of
carrier based signals, making the existing systems useless."
Harmuth's reply: "No, it is *your* carrier based systems that are
creating wide splatters in *my* Hadamard spectrum and rendering my
system useless."
Now imagine that the Hadamard stuff extends over 2.8 kHz.
Ivory Tower? Look up Walsh Functions and Hadamard transforms on the
web and you might find that some of your favorite digital modes
actually use them (but over a narrower bandwidth).
I still have Harmuth's "Non-sinusoidal Waves for Radar and Radio
Communication" (1981, ISBN 0-12-014575-8) on my book shelf.
Fascinating read (stuff like how to construct bandpass filters for
Walsh functions) if you like thinking out of the box. There is even a
section on "Bandwidth Required for Teletype and Data Links."
73
Chen, W7AY
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