Jeff Liebermann wrote:
On Wed, 16 Dec 2009 11:35:54 -0500, Michael Coslo
wrote:

Jeff Liebermann wrote:
I don't want to comment on the legal part of the puzzle (because I
already have a headache). However, it should be obvious that there's
a potential conflict between unlicensed Part 15 operation, and
licensed part 97 operation on 2.4GHz. Place your bets and blast a way
with kilowatts on 2.4Ghz. Will 800,000 licensed US hams prevail over
perhaps 300 million unlicensed wireless devices? Want to bet on who
will win before an FCC tribunal? If there is a conflict, I'll place
my bets on Part 15.

No one in their right mind is going to be running that much power -
being line of sight, at those frequencies, there isn't any point.

Most of the Wi-Fi installations are setup to go through walls where
power is helpful. Not exactly line of sight. Some of the outdoor
installations are installed by WISPs (Wireless Internet Service
Providers) that sometimes user maximum legal power amplifiers. You
can also buy relatively high power client radios:
http://www.ubnt.com/products/xr2.php
That's +28dBm or 630mw, which is considerably more power than the
typical 50mw radios. There are also bi-directional power amplifiers
allegedly sold only for ham, government, and industrial use only:
http://www.ssbusa.com/kunamp1.html
and the video equivalent:
http://www.bhphotovideo.com/c/product/505472-REG/RF_Video_AMP_5000M_10_AMP_5000M_10_High_Power.html
from of all places a camera store. I've also helped identify and shut
down 3 such overpowered installations.

What's happening is as the 2.4GHz band gets more and more polluted,
some individuals seem to think that the solution is to increase their
TX power level. That's resulting in a very slow power war. The Wi-Fi
device manufacturers have caught on and are now advertising "high
power" devices, which seems to be anything over +20dBm (100mw).
Various pundits have predicted a power war, which fortunately hasn't
happened.

Regarding your hypothetical situation though, The likely outcome is that
the Amateur would be asked to turn down the power.

That's exactly what has happened in one of the situations that I was
involved. He didn't realize he was causing a problem and was very
cooperative. I also monitor the FCC enforcement actions:
http://www.fcc.gov/eb/AmateurActions/Welcome.html
and have not seen anything on 2.4 or 5.6GHz that required official
action. However, I do know of some warnings sent to WISPs over the
last 10 years or so for using too much power. So far so good.

They usually ask the
two parties to work together to get rid of the interference. But the
real onus is on the part 15 device owner. Dunno if you read the F.C.C.
enforcement actions, but the licensed service still "wins".

That's exactly the problem I mentioned. The licensed ham using 2.4Ghz
is within his rights to use 1Kw. He can also legally cause
interference to unlicensed devices without much consideration. So it
is written, and it must be. However, all it's going to take is a few
industry groups (i.e. lobbying interests) to claim that ham radio
operation on 2.4Ghz is somehow detrimental to the economy by impacting
Wi-Fi equipment sales, and I suspect there will be changes that impact
ham radio. Please consider my comments more as a warning than as a
denunciation.

That was the tactic for the BPL folks. It has to be faced down whenever
they bring it up. The tail should never wag the dog. It becomes doomed
anyhow, because when the device with special privileges starts
interfering with other devices with special privileges, who wins then?
We cannot do an "Animal Farm" Some are more equal than others situation
without chaos.


BPL was an
attempt by economic interests to turn technical reality aside for
pecuniary reasons, but it looks like th elicensed services are going to
win that war now also.

BPL is going to die because the electric utility companies are not
seeing any revenue from the exercise, are getting some really bad
press, and really don't need the hassle. The interference issue gets
the press, but the decisions are always made on the basis of dollars.

BPL proponents allowed people to believe that they were going to just
send the signals along the lines from some sort of "head end" site, and
they would be there for the tapping. In fact, they were a last mile
solution the Fiber would have to be run almost to the house, then the
signal injected into a H-V line - the bpl signals could not survive
going through transformers - finally a device to couple the BPL signal
from the HV to the Household line after the transformer would allow the
signal into the house.

That's bad technology on so many levels it's obvious that the decisions
were based on economics and perhaps some politics (not R vs D, but the
idea that belief trumps science, that the intuitive idea of sending
multiple signals on one wire just has to work.

Are we going to bet our life on that H-V line isolator - injector never
failing closed, and allowing Several KV into our home electrical system?

But the final issue for me was that the source of the data signal had to
come almost to my house. Clean, yummy, digital goodness being degraded
to a shaky easy to disrupt DSL speed signal. No thanks, folks. But let's
talk about get me hooked directly into that fiber, pleeze!


After the ARRL got hold of the original documents
the F.C.C. used during the run up to BPL, and founf out thet the
commission ignored their own engineers findings, then tried to hide that
fact, it kinda let the air outta that tire.

True. Much credit to the ARRL for being able to do that. Still,
nothing has really changed at the FCC end. BPL systems that are
leaking well over established limits are still "working on the
problem". Most are still running in what is becoming a permanent
"trial" mode.
http://p1k.arrl.org/~ehare/bpl/ex2.html

Fortunately, they are going to eventually go away. Unless BPL is going
to become some sort of welfare system with companies sinking money into
it's maintenance for just a few customers.

I had always wondered what was going to happen to BPL systems when the
sunspot cycle hits it's peak.
I'd been assured that propagation wouldn't have any effect on it, but
we'll see.


Meanwhile, a rather large number of HomePlug devices, which is
essentially BPL for home internet, are being sold. They don't leak as
much RF power as real BPL systems, but still manage to make plenty of
noise:
http://www.mds975.co.uk/Content/amateur_radio_BPL_interference.html
Hmmm... It's QRN, not QRM. Oh well.
http://p1k.arrl.org/~ehare/bpl/Testing_HomePlug.htm
At least the ARRL is involved. Some HomePlug devices have
pre-programmed notch filters to reduce power on "sensitive"
frequencies which include ham bands.

All eventually doomed to failure.

If I might conjecture, I think that the current crop of EE's did not pay
any attention to RF while grooming themselves for the brave new future
of "Everything is digital". The HF bands are an unruly beast. They are
prone to static, they are prone to propagation, where at some times a
strong signal can't go much of anywhere, and at other times a milliwatt
works the world. And to make things worse, the propagation varies by
frequency.

For most digital wireless situations, you want a noise free, propagation
free, short range system. HF will never satisfy these requirements. Some
times at sunspot minimum, they might look a little better, but even
then, they just aren't a good choice. Hell, VHF is only just usable.
Gotta be well into UHF before you get good stable conditions

But The new crop of engineers and econo-politicians would like to impose
their digital reality on sections of RF spectrum that just aren't going
to cooperate.


- 73 de Mike N3LI -