"Steve Stone" wrote in message
et...

You won't hear much of anything under 400 mhz once broadband over
power lines ramps up to full
bore.

Do a gOOgle search on BPL,

Steve

I'm lazy. How 'bout you gOOgle up some links concerning this "You won't
hear much of anything under 400 mhz " business?

Oh, yeah. Don't forget to share your knowledge with the TV and radio
networks. For some reason, they don't seem concerned.

Frank Dresser

"Frank Dresser" wrote in message
news

"Steve Stone" wrote in message
et...

You won't hear much of anything under 400 mhz once broadband over
power lines ramps up to full
bore.

Do a gOOgle search on BPL,

Steve

I'm lazy. How 'bout you gOOgle up some links concerning this "You won't
hear much of anything under 400 mhz " business?

Oh, yeah. Don't forget to share your knowledge with the TV and radio
networks. For some reason, they don't seem concerned.

400 MHz is a bit of an exaggeration. BPL will cause considerable
interference up to it's limit of 75MHz, and may cause some harmonic
interference above that (it IS square wave after all, and high in harmonic
content).

It won't (or shouldn't) affect the AMBCB, since it is supposed to start at
1.8 MHz. However, there have been several tests performed by hams and some
labs (see the ARRL website www.arrl.org), and several countries have already
banned BPL because of extreme interference to other services, including HF
broadcast and amateur radio services. I don't remember the exact numbers,
but basically if you are within 30 feet of a BPL line, you will receive in
excess of S9 (some tests have shown 30 dB over S9) of interference.

"Brenda Ann" wrote in message
...


400 MHz is a bit of an exaggeration. BPL will cause considerable
interference up to it's limit of 75MHz, and may cause some harmonic
interference above that (it IS square wave after all, and high in
harmonic
content).


Oh, I know. I've done my fair share of usenet posts on the BPL topic.
The original poster makes a very good point, though. It is easy to
research.



It won't (or shouldn't) affect the AMBCB, since it is supposed to
start at
1.8 MHz. However, there have been several tests performed by hams and
some
labs (see the ARRL website www.arrl.org), and several countries have
already
banned BPL because of extreme interference to other services,
including HF
broadcast and amateur radio services. I don't remember the exact
numbers,
but basically if you are within 30 feet of a BPL line, you will
receive in
excess of S9 (some tests have shown 30 dB over S9) of interference.



I really doubt BPL will have any noticable effects on AM/FM/TV
reception. After all, the networks haven't used any of their
considerable clout in Washington in the BPL fight. I suspect consumer
electronics will be most subject to any BPL effects throught the power
cord and not the antenna terminals. If this has been a problem in the
test areas, I'm not aware of it.

But I wonder if BPL will work as promised and if it will be a good deal
for the consumers. Power lines are an awfully primitave way to deliver
high speed access, and I can imgaine alot of problems. If BPL doesn't
work out, the utilities might have to fall back on BWP (Broadband over
Water Pipes).

Frank Dresser

In article ,
"Brenda Ann" wrote:

"Frank Dresser" wrote in message
news

"Steve Stone" wrote in message
et...

You won't hear much of anything under 400 mhz once broadband over
power lines ramps up to full
bore.

Do a gOOgle search on BPL,

Steve

I'm lazy. How 'bout you gOOgle up some links concerning this "You won't
hear much of anything under 400 mhz " business?

Oh, yeah. Don't forget to share your knowledge with the TV and radio
networks. For some reason, they don't seem concerned.

400 MHz is a bit of an exaggeration. BPL will cause considerable
interference up to it's limit of 75MHz, and may cause some harmonic
interference above that (it IS square wave after all, and high in harmonic
content).

It won't (or shouldn't) affect the AMBCB, since it is supposed to start at
1.8 MHz. However, there have been several tests performed by hams and some
labs (see the ARRL website www.arrl.org), and several countries have already
banned BPL because of extreme interference to other services, including HF
broadcast and amateur radio services. I don't remember the exact numbers,
but basically if you are within 30 feet of a BPL line, you will receive in
excess of S9 (some tests have shown 30 dB over S9) of interference.


Data communications occupy wider bandwidths than the stated clock rate.
It is not unreasonable to expect harmonics 3 to 5 times the clock rate
because the signaling uses square waves and there is significant power
in the odd harmonics.

--
Telamon
Ventura, California

"Telamon" wrote in message
...


Data communications occupy wider bandwidths than the stated clock
rate.
It is not unreasonable to expect harmonics 3 to 5 times the clock rate
because the signaling uses square waves and there is significant power
in the odd harmonics.

--
Telamon
Ventura, California

A square wave, itself, won't convey much information. It needs to be
modulated, and the modulation would have to effect the symmetry and
result in both odd and even harmonics.

I don't know what sort of modulation BPL is using. I can imagine
hundreds of low amplitude sine wave carriers from 2 to 60 Mhz, all of
them phase modulated. In that case, I don't think there would be much
harmonic output. This would certainly still be a big problem for the
radio hobbyist, but not so much for the FM/TV user. There have been
several BPL tests in various communities, and it doesn't seem to have
wiped out normal broadcast use.

If BPL caused enough bothersome interference to keep people in the test
communities from their TVs and radios, the National Association of
Broadcasters would have squashed it like a bug.

Frank Dresser

"Frank Dresser" wrote in message
...

"Telamon" wrote in message
...


Data communications occupy wider bandwidths than the stated clock
rate.
It is not unreasonable to expect harmonics 3 to 5 times the clock rate
because the signaling uses square waves and there is significant power
in the odd harmonics.

--
Telamon
Ventura, California

A square wave, itself, won't convey much information. It needs to be
modulated, and the modulation would have to effect the symmetry and
result in both odd and even harmonics.

I don't know what sort of modulation BPL is using. I can imagine
hundreds of low amplitude sine wave carriers from 2 to 60 Mhz, all of
them phase modulated. In that case, I don't think there would be much
harmonic output.

Digital comms are purely square waves. The modulation is FSK or similar
(generally)... in other words, the on-state is one frequency, the off state
is another. This creates a chain of square waves which themselves are not
modulated. The bandwidth, in this case 75 MHz, is how many on/off states
there are in one second. This is also concurrent with bitrate. Compression
schemes can raise the apparent bitrate, however the actual bitrate is the
same as the frequency used. I'm not sure how they do the band notching that
Japan tried before they tossed out the idea completely.

"Brenda Ann" wrote in message
...


Digital comms are purely square waves.

I'm using the term "square wave" to mean a sharp cornered pulse train
with an exactly 50% duty cycle. There's not much information there.
You've seen one pulse of the square wave, you've seen them all.


The modulation is FSK or similar
(generally)... in other words, the on-state is one frequency, the off
state
is another. This creates a chain of square waves which themselves are
not
modulated.

And the square wave is recovered after only after demodulation of the
sine waves. The modulation doesn't necessaraly create harmonics, but it
does create sidebands.

This guy likes to use triangle waves in his illustrations:

http://www.cs.ucl.ac.uk/staff/S.Bhat...es/node12.html


The bandwidth, in this case 75 MHz, is how many on/off states
there are in one second. This is also concurrent with bitrate.
Compression
schemes can raise the apparent bitrate, however the actual bitrate is
the
same as the frequency used.

The carriers can be both amplitude and phase modulated to increase
bitrate.

Given that the BPL is usually described as a spread spectrum technology,
I'll assume there's many carrier frequencies.

I'm not sure how they do the band notching that
Japan tried before they tossed out the idea completely.




Doesn't Japan have a higher percentage of SWLs and radio amateurs than
the US? I don't think most Americans will much care about BPL unless it
effects the TV. I'll bet the BPL traps at 3.58 MHz work just fine.

Frank Dresser

From:
http://www.qrpis.org/~k3ng/bpl.html
-----------

Q: What is intermodulation?

A: Intermodulation is the mixing of radio signals which produces new radio signals. Think of
it as radio waves having children. But just how do radio waves have children ?

This mixing is caused by what are called non-linearities. One non-linear electronic component
that you find in most any electronic device is a diode. When multiple radio signals are run
through the diode, they mix together. Let's say we have a 4 Mhz signal and a 6 Mhz signal
going into the diode. We would then get:

4 + 6 = 10 Mhz

6 ? 4 = 2 Mhz

4 and 6 Mhz had two ?children?, 2 and 10 Mhz !

Now, non-linearities are usually good. This phenomenon is used in just about every radio
device to either create a signal to be transmitted, or receive a signal that you hear or see.
But, non-linearities can occur where you don't want them and then in causes problems. One such
place is in power lines. Bad, corroded connections or dissimilar metals touching can create
natural diodes that act like mixers and produce this intermodulation.

So, let's take a BPL signal and for the sake of discussion, say it's a grossly simplified
consisting of radio signals at 1, 5, 8, 9, and 12 Mhz. Some of the intermodulation products
that could be created would be:

1 + 5 = 6 Mhz

8 + 9 = 17 Mhz

9 + 12 = 21 Mhz

12 ? 9 = 3 Mhz

But you could also have what is known as third order products:

1 + 9 + 12 = 22 Mhz

8 + 9 + 12 = 29 Mhz

8 ? 5 + 12 = 15 Mhz

Or even:

2 * 12 = 24 Mhz

(9 ? 5) * 12 = 48 Mhz

You can do the math and figure out each permutation, but you get the idea. If we took a real
BPL signal that has signals from 1 ? 80 Mhz the number of products and where they would fall
are mind-boggling. The resulting intermodulation products in a system could extend well above
the band BPL proponents want, falling into FM broadcast, VHF TV, Aeronautical, and more public
safety bands. This is just another reason why BPL is so problematic.

It's arguable that such non-linearities in power lines are exhibited as arcing connections,
something that most power companies are actively searching for these days as the RFI (radio
frequency interference) effects are well understood. These maintenance issues will be
addressed quickly by well run utilities. However, non-linear loads are common in homes, light
dimmers being the first devices that come to mind. Theoretically, these devices could create
intermodulation that would in turn be radiated by the house wiring and outside power cabling.

It's hard to generalize about all digital communication. I think
BPL is some kind of phase modulated OFDM as Frank says, so in that
case you could use essentially rectangular pulses (in practice there
is probably some roll-off and guard time to boot). Each individual
tone would actually occupy a bandwidth much greater than its keying
rate, but since each tone's keying rate is so low compared to the
total bandwidth, the net effect is minor, again exactly as Frank
says.

For single carrier high date rate systems however, the last thing you
want to use is rectangular pulses. The spectrum won't have discrete
harmonics but it will look like (sin(x)/x)^2 in frequency with
significant energy beyond the Nyquist frequency. In those applications a
waveform that falls off in time as t^2 is generally used, though there
are other options, like minimum-shift keying, which can be looked at
either as continuous phase FSK or QPSK using smooth shaped pulses.
Continuous phase modulation has some complications though.

Oz


Brenda Ann wrote:
"Frank Dresser" wrote in message
...


A square wave, itself, won't convey much information. It needs to be
modulated, and the modulation would have to effect the symmetry and
result in both odd and even harmonics.

I don't know what sort of modulation BPL is using. I can imagine
hundreds of low amplitude sine wave carriers from 2 to 60 Mhz, all of
them phase modulated. In that case, I don't think there would be much
harmonic output.


Digital comms are purely square waves. The modulation is FSK or similar
(generally)... in other words, the on-state is one frequency, the off state
is another. This creates a chain of square waves which themselves are not
modulated. The bandwidth, in this case 75 MHz, is how many on/off states
there are in one second. This is also concurrent with bitrate. Compression
schemes can raise the apparent bitrate, however the actual bitrate is the
same as the frequency used. I'm not sure how they do the band notching that
Japan tried before they tossed out the idea completely.

In article ,
Larry Ozarow wrote:

It's hard to generalize about all digital communication. I think
BPL is some kind of phase modulated OFDM as Frank says, so in that
case you could use essentially rectangular pulses (in practice there
is probably some roll-off and guard time to boot). Each individual
tone would actually occupy a bandwidth much greater than its keying
rate, but since each tone's keying rate is so low compared to the
total bandwidth, the net effect is minor, again exactly as Frank
says.

For single carrier high date rate systems however, the last thing you
want to use is rectangular pulses. The spectrum won't have discrete
harmonics but it will look like (sin(x)/x)^2 in frequency with
significant energy beyond the Nyquist frequency. In those applications a
waveform that falls off in time as t^2 is generally used, though there
are other options, like minimum-shift keying, which can be looked at
either as continuous phase FSK or QPSK using smooth shaped pulses.
Continuous phase modulation has some complications though.

I haven't read how BPL is supposed to work but is it reasonable to
expect that a encoding scheme would be used that would shift the
spectrum requirements downward so that increased coupling would be
needed across the transformers in the power system?

--
Telamon
Ventura, California