From: John Smith on Tues 9 Aug 2005 17:46

Len:

The BPL modems I have seen go from the bottom of low audio freqs up to
~300Khz. I don't know where anyone ever got the idea this range was even
going to go into the am broadcast band! At some of those freqs, a full
wavelength can be measured in miles... and, the "transmission line"
becomes a few small wavelengths...

We aren't talking about the in-building carrier-current kind of
thing. This is HIGHER SPEED stuff occupying HF and on up to
about 80 MHz.

I think they are doing, REALLY, what they say they are doing, they are now
simply in the process of TESTING it, what the final results of all this
are/"will be" ???

It's primarily MARKET testing...plus ordinary Field Trials.
Seems to be very difficult to get some real guts-contents kind
of information but it IS broadband, much wider than the best
carrier-current stuff.

There's been several field tests for RFI on the installed Test
(Market) locales. That Testing began 3 years ago or so. It
has gone on longer in Yurp.

You can begin looking into BPL at the ARRL website and continue
on to some very large RFI testing reports by the government and
private metrology companies, checking out the links. FCC ECFS
has lots and lots and lots of Comments on it. Much of that has
been thrashed-out in words and figures in 2003 and 2004.

I am just stating amateurs and the interference it MAY pose to their HOBBY
is NOT ANY REASON(S) to be given ANY consideration what-so-ever, it is not
the majority--the greatest good for the greatest number...

The "majority users" of HF may NOT be just radio amateurs.

Aeronautical Radio Inc., ARINC, contracts to do HF comms with
air carriers on long international routes. Those sites CAN
be interfered with, not a good thing with the "heavies" (747
and the like) carrying lots of passengers.

The U.S. government has about 2500 HF-capable stations in the
contiguous states, AK, and HI, plus PR and other U.S.
territories. Those are periodically netted as a SHARES
exercise. Most of those are equipped with ALE and can jump
frequency as needed depending on local QRM.

There's still a couple of low HF freqs for maritime emergency
comms. Maritime radio services still use HF especially on
deep water; they've gone to single-channel SSB for voice and
Teleprinter Over Radio for data in place of electromechanical
teleprinter. There's the WWV and WWVH time-frequency standard
stations; not everyone uses (or can get) the 60 KHz WWVB
signal; still useful for medium-accuracy metrology.

The "low-VHF" band for PLMRS (Private Land Mobile Radio
Service) includes freqs in high-HF as well as from 30 to 50
MHz. Lots and lots of those still working in USA.

"SW BC" can kiss some of their audience goombye wherever a
BPL is running since it will effectively mask reception of
both foreign and domestic stations. There are more SW BC
bands than there are ham bands on HF.

The "occupiers" of HF can be found at the NIST site as
reports and documents, going back two decades if you like
that sort of thing. They and the NTIA work together to
try future planning for the EM spectrum; FCC cooperates
by using that information for decision-making on specific
radio services. FCC OET (Office of Engineering and
Technology) concentrates on Mass Media radio services
(broadcasting) for BC standards, separation of stations
by locale, and useful info on BC antennas.

In Yurp there's similar but their "BPL" (they use another
acronym) is older. The first system was a test in Norway.
Lots of info on the web for that, just not concentrated
neatly as for the USA. Japan has done some trials and was
NOT happy with the results.

Ackshully, the electric power transmission people have been
using a BPL-predecessor longer for telemetry and control of
the power lines they are controlling. Slower-speed stuff
which may be what you've seen. Hasn't been a bed of roses
for them, either, according to some of the Commentors in
the FCC ECFS on Access BPL, a couple of those being P.E.s
who were involved in that "pre-BPL" work. Electric power
folks have the advantage that few other folk live close to
the Kilo- and Mega-Volt electric power transmission lines;
them MVe lines be ten kinds of noisy anyway.

Access BPL systems in Market Testing have been using the
"medium" (around 4 KV) distribution lines. Those are the
ones that connect to transformer primaries (such as on
utility poles) so that the secondaries can supply 230/115
Volt drops to individual subscribers. Some kind of couplers
manage to get the KV line data to the drop lines for
residential broadband service (two-way) with most systems
but at least one uses a WiFax-kind of coupler to get to an
individual residence. That sort-of isolates the data line
from the KV. WiFax is a low end of microwaves or high UHF.

I would presume that the data rate of these BPL providers
is similar to the broadband data supplied through wideband
cable such as TV cable service. TV allows HF to 50 MHz for
broadband data downstream since it doesn't interfere with
present-day TV channel 2; that's a 40+ MHz wide path for
fairly-good-rate data. TV itself uses about 1 GHz bandwidth
(give or take) for analog TV; larger for digital TV through
fiber optic main distribution (analog for the drops).

"Discontinuities" in transmission lines (for RF, data, etc.)
are the culprit for high VSWR and thus reflected power
which winds up spritzing out into space (around the lines).
Discontinuities come from everything...jump to a different
characteristic impedance, changes in conductor wires,
weird loopy jumpers, pole-mounted circuit breakers. The
electric power lines were NEVER characterized as RF or
DATA transmission lines...ONLY for 60 Hz AC, never higher
in frequency.

rfi emi