Here some facts to consider and then I'll get busy with my comments to
the NPRM:
Any mode that uses AFSK modulation of an SSB radio will be no wider than
3 kHz, obviously. If the radio could be modified with wider filters,
the signals could get wider, too, but the phase/amplitude
characteristics of the transmit chain needs to have much cleaner
characteristics than for voice. (Direct FSK has different limiting
issues.) It would take a whole new modulation/transmission scheme to do
wider-band data and that would demand an SDR with very low IMD in the
amplifier chain. The SDR part is straightforward since that's mostly
math and FPGA programming. The RF amplifier part is not so easy and
will require advanced techniques from the wireless data industry such as
adaptive pre-distortion. (One benefit to SSB/CW operation from such an
adaptation would be cleaner transmitters.)
We should take some comfort in the fact that there aren't many wideband
data signals on shortwave commercial or military channels. If wideband
data was easy, they would be doing it now. They are not. Here is an
extensive table of characteristics for many known HF data modes,
including military and commercial signals:
http://www.sigidwiki.com/wiki/Category:HF
The widest signal in the table that is not a radar or a jammer is DRM
(Digital Radio Mondiale) at 20 kHz and that's a "phone" signal for hi-fi
audio. The data version of DRM is much narrower and has been used on
the ham bands for SSTV in the image sub-bands. The widest pure data
signal in the table has a 6 kHz bandwidth. We might be concerned about
the authorization of spread spectrum and wideband OFDM techniques but
neither of those are authorized emissions below 30 MHz. So...even if
the FCC declines to put a bandwidth limit of 6 or even 10 kHz on amateur
signals, we're not going to see a big influx of roaring, high-speed data
anywhere on HF. The physics of propagation just doesn't work and it
takes a lot of engineering and equipment to make even the narrower modes
perform. I think they ought to keep a bandwidth limit because the HF
bands are a shared resource but that's a behavioral concern.
= = =
What kind of a need is there for regional HF digital in emcomm? Well,
earthquakes and hurricanes, for starters. The Pacific NW just had their
big tsunami/earthquake drill (The Great ShakeOut) and having lived there
for a long time I can tell you it is not wild speculation that comms
could be taken out for several million people in three states over
several hundred miles along the I-5 corridor between Grants Pass, OR and
Vancouver, BC. VHF/UHF ain't gonna get 'er done. The emergency groups
up there are prepared to use HF (either Winlink systems or NBEMS) to
coordinate on a state-wide basis. Drill traffic is often passed over
HF, sometimes through mailboxes hundreds or thousands of miles from the
area due to the skip zone.
We have enjoyed a ten-year hiatus in big hurricanes hitting the
southeast U.S. but HF is a prime resource for recovery from really big
storms. Here in Missouri, we have localized disasters (mostly) but
there is no state-wide VHF+ system to support communications with the
state Office of Emergency Services. So the need is real.
= = =
The concern about session-based protocols (including AX.25) being hard
to monitor is certainly valid. PACTOR modes do support the ability to
monitor the packets (with another PACTOR modem) for station ID. The
data is usually compressed, so unless you capture everything perfectly,
you won't be able to tell what is being sent. (I can't decipher
cyrillic or katakana morse, either...) Here's a possible solution -
create an network of PACTOR modems that listen to the various signals in
monitor mode and post the station IDs and any other associated data
online like the RBN system. A "mode deciphering monitor" program that
runs on one's personal SDR would be a worthy project, too. Simple
matter of programming :-)
The "hidden transmitter" problem is always a concern, even on CW/RTTY
where a station who can't hear me tries to communicate with a station I
can hear. Yes, the channel-busy detectors could be better, but the
operators have to engage. This is why I lobbied (successfully) for a
set of new questions in the General Class pool that directly address the
requirements of a control operator to listen before initiating contact
with a remote-control station. Will they do it? Some will and some
won't, but at least they've had to learn about the requirement.
I've been clobbered by phone, RTTY, SSTV, and even CW signals from
stations who could clearly hear my signal and just didn't care. What
did a famous phone contester once say, "A clear frequency is where the
needle comes off the right-hand peg a little bit." Data stations aren't
the only offenders in this regard.
= = =
There is some historical precedent as to the benefits of loosening
restrictions on amateur data experimentation. The FCC NPRMs in the late
1970s and early 1990s liberalizing amateur data modes resulted in a huge
explosion of amateur innovation such as packet radio, various TOR modes,
and other interesting developments. This is generally viewed as a good
thing. Your cell phone, by the way, probably includes at a deep level
some data protocols developed for amateur radio that were adapted for
commercial use. (This is described in "A History of QST, Volume 1 -
Technology," published in 2014.) We have mostly forgotten what "data"
was like (non-existent) in the days before hams could use ASCII.
= = =
Opening up bandwidths is just not going to be the calamity some of us
are concerned about. There will be some irritation (including mine) as
we adjust to new patterns of band use (and the kids will play on our
lawns) but I am willing to accept the risk, support innovation that
responds to new needs, use my big knob, and move on.
73, Ward N0AX
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