Brenda Ann wrote:

"Frank Dresser" wrote in message
...

Will BPL have the same effect on military radio as it has on radio
hobbyists? Don't they have spread spectrum capability which is highly
resistant to interference?

Frank Dresser


Thing is, BPL is also spread spectrum.. would not two spread spectrum
systems on the same bands interfere with one another??

Yes, but to a limited degree.

One characteristic which distinguishes a spread-spectrum
(whether frequency-hopping, or direct-sequence) system from
a channelized one, is the gradual way the channel
signal-to-noise ratio can degrade as more stations are added
in the same spectrum space. This "graceful degradation" is
in stark contrast to interference in standard
single-frequency applications, where a collision of two
signals means no link.

Think of two different transmitters sharing the same 1000
frequencies. Each "hops" to a new frequency every few
milliseconds at most. If both systems use different channel
sequences, it's just occasionally that both would land on
the same frequency and interfere with each other. And even
in this case, the total amount of time where they're
mutually interfering is perhaps a millisecond or less. So
the extra signal sharing the frequency has mostly the effect
of making the channel a tiny bit noisier for all users, but
not to blot out other signals.

As you add more and more spread-spectrum stations, the
probability of a "channel collision" of course increases.
However, by carefully choosing the sequences and making sure
they don't accidentally "lock horns" in synch for a while
following the same sequence of frequencies, the quality of
the link degrades slowly with each new station.

I suspect this "graceful degradation" property of spread
spectrum is more of a driving force than the potential
security and stealth that this system provides. It allows
more users to share the same small frequency slice, than
would be possible if you just put narrow-band FM equipment
and jammed them together as close as possible.

Funny how often unexpected benefits spin off of basic
research. Here's to renewing science and basic research.
Not everything important to business can be measured in
quarterly profits. Our competitors, who seem to get this
better than a lot of US companies do, will eat our lunch for
us if we don't start thinking long-term again. IBM and HP
"get it". It's Congress that we need to wake up next. :)

-- Ross

You're right about that. Unfortunately, the standard business plan is to
make as much as you can in the short term and then dump the company. They
have no interest in anything that won't pan out in 6 months.
"Ross Archer" wrote in message
...
Our competitors, who seem to get this
better than a lot of US companies do, will eat our lunch for
us if we don't start thinking long-term again. IBM and HP
"get it". It's Congress that we need to wake up next. :)

-- Ross

"CW" wrote in message news:uca3b.278911$uu5.62460@sccrnsc04...
They probably do but not in widespread use nor is it likely to be. They do
also have the capability to replace most of that HF traffic by satellite.
They did, at one time, start to scale back the HF ops in favor of satellite
but decided that was a bad idea from a reliability standpoint. They do have
the satalite capablity but maintain HF to. The military, in any case, is
only a part of the government HF operation.

Right: Didja ever add up the number of published MF/HF freqs just the
Coast Guard and the HF air traffic controllers use?? And those are
just a few of the published gummint-used freqs. Then come who the hell
knows how many unpublished freqs also used by other civil gummint
types.

If bpl has the capability of not
using certain segments of the band, due to the amount of space that would
have to be left alone, the bpl spectrum is going to be pretty holy.

It would be one big hole, "selective BPL interference" is a ridiculous
and completely unworkable concept.

In any
case, I really don't think it is a viable technology, I seriously doubt it
will be the major rf disaster that some are saying it will be and I don't
think it will last long if it gets off the ground at all.

If it's allowed to get off the ground at all a huge amount of damage
will be done even if it does eventually peter out. The closing the
gate after the cows get out syndrome, etc.

As far as BPL being an RF disaster is concerned I've travelled twice
to one of the BPL pilot areas specifically to listen to the stuff
hands on. Been there, done it myself and I need to tell you that yes
BPL is a potential HF/VHF disaster which needs to be squashed *before*
it even gets off the ground.

Anybody who belives otherwise needs to get off their butts and away
from their keyboards, pack up a rig and actually go listen to stuff
before they spout off about it.

Brian Kelly w3rv

"Frank Dresser" wrote in message ...
"DickCarroll" wrote in message
om...
"Frank Dresser" analogdial@worldnet




Hey Frank, where'd you ever get the idea that radio *isn't* open to
the public?
I never knew anyone whatever who wanted a ham radio license who was
barred from getting one. There is a small matter of qualifying for it,
of course, as there is in every endeavor where others can and will be
impacted when the licensee knows not which way is up. But it has
always been open to all comers.


OK, amateur radio is open to the public. But nearly all amateur radio
activity is either contacts between hams or some sort of test. I'm under
the impression that amatuers broadcasting what might be considered
entertainment programming to the public is banned. Am I wrong about that?




No, sounds accurate to me.



Now if you're talking "open" like CB is open, that's a horse of an
entirely different color.

Dick

More like pirate radio. I've heard some very entertaining stuff, and I hope
to hear alot more. I know that time can be bought on an independent
broadcaster, but I'd really like to know why what Alan Maxwell and the other
do is illegal. I think hobby broadcasting would bring alot of positive
interest to SW radio.


As always,it's a $$$$$ thing, of course.

In article ,
Frank Dresser wrote:
[snip]

Will BPL have the same effect on military radio as it has on radio
hobbyists? Don't they have spread spectrum capability which is highly
resistant to interference?

Frank Dresser



Spread-spectrum is highly resistant to narrowband interference. BPL
develops wideband interference. What the military depends on is the
physics that any remote jammer trying to create wideband noise would need
to be immensely powerful, because a wide band of loud-at-a-distance noise
would have to have substantial energy at every frequency. BPL defeats
this by putting the transmitting antenna very near the receiver, so the
noise source need not be powerful to be loud at every frequency.
--

R F Wieland Newark, DE 19711-5323 USA 39.68N 75.74W
Icom R75 Heathkit GR-81 Inverted-L in the attic
Reply to wieland at me dot udel dot edu

"Robert F Wieland" wrote in message
...
In article ,


Spread-spectrum is highly resistant to narrowband interference. BPL
develops wideband interference. What the military depends on is the
physics that any remote jammer trying to create wideband noise would need
to be immensely powerful, because a wide band of loud-at-a-distance noise
would have to have substantial energy at every frequency. BPL defeats
this by putting the transmitting antenna very near the receiver, so the
noise source need not be powerful to be loud at every frequency.
--

R F Wieland Newark, DE 19711-5323 USA 39.68N 75.74W
Icom R75 Heathkit GR-81 Inverted-L in the attic
Reply to wieland at me dot udel dot edu


That's what I'd expect. But I don't know if the BPL system will dirty
enough, or close enough to significantly interfere with military
communications. I suppose the military has sent people out to take readings
like Ed Hare did. Anyway, I'm thinking the biggest threat to BPL isn't
outside opposition, but the spikey wideband trash normally found on power
lines.

That's it! BPL is a wives' conspiracy to get their husbands to start
vacuuming the freakin' carpet!

Frank Dresser

On Wed, 27 Aug 2003 09:57:46 +0000 (UTC), Ralph Aichinger
wrote:

And I think military users could change to VHF or UHF, even sat
communications anyway if they wanted. They could also keep BPL
out of special areas. I doubt military users in suburban environments
give a damn about HF.


ARINC *has* filed comments. Apparently, one of their receive sites
near San Francisco was severely affected by some Part 15 equipment in
a house nearby. One of their 3 MHz frequencies was rendered unusable.

The NTIA will step up to bat for the military and government HF users.

Take care,

Dave

David Moisan, N1KGH, SKYWARN
Invisible Disability: http://www.davidmoisan.org/invisible_disability.html
GE Superradio FAQ: http://www.davidmoisan.org/faqs/supe.../gesr_faq.html
Sangean ATS-909 FAQ: http://www.davidmoisan.org/faqs/sangean/ats909faq.html