BPL strikes another win ...
 

John Smith I wrote in
:

Dave Oldridge wrote:

...
Lots of times. My CW error-correcting hardware is excellent, is
always on, and conveniently located in my head.

But you're missing my point. A modem is always an analog device.
And if it's listening on a frequency with a loud signal on it, then
it can be saturated by that signal. I've not seen many that could
copy the heterodyne. Mostly they just stop giving any recovery at
all.


There are very rugged modems. Most people just accept the modem which
was included with their computer. A cheap modem implemented, almost
totally, in software; these can exhibit poor performance.

You get what you pay for, and like I say, BPL is a developing
technology; or, in other words, problems must be found before they can
be fixed. Your KW+ signal will be a great aid, possibly, in that
direction ...

Having worked in the software/algorithm/data-compression aspects of
modems, I have experienced high levels of line noise on standard
modems which needed new techniques to solve ... Although I have seen
many instances where line noise is at such levels even speech is
horrible, and data xmission slows to a crawl, there are few instances
where it becomes absolute zero--baring the physical disconnection of
the line.

If you are inducing interference of a noticeable level in a persons
home/business that is noticeable, it will be more than just noticeable
on the BPL modem!

Not so. Most home and business equipment is not DESIGNED to receive
signals on frequencies where I operate (the single exception being some
cable systems that use the 2m band). Nor is it using wiring that is WIDE
OPEN to my signals. In fact the worst offenders are stereo systems with
parallel speaker leads that need only a bit twisted pair, bypassing and a
ferrite or two to eliminate all the pickup. Shielded wires may also need
toroids to eliminate magnetic pickup that goes right through the shields.

But sending an HF signal down an open power line is not just inviting
interference, it's BEGGING for it, since you've given the system a very
large antenna and put a sensitive receiver on the end of it.
DELIBERATELY. That's like designing a gun with a plugged barrel and then
firing it!

--
Dave Oldridge+
ICQ 1800667

BPL strikes another win ...
 

John Smith I wrote in
:

Dave Oldridge wrote:
John Smith I wrote in
:

Dave Oldridge wrote:
John Smith I wrote in news:fa4i2a$jve$1
@news.albasani.net:

Dave Oldridge wrote:

...
You need a good book on digital error correction algorithms in
digital communications.

Unless you have constructed a real rf jammer (white noise really),
BPL will eat up any legitimate amateur communications you can
throw at it ... however, rumors do prevail, like the one about the
tin foil hat.
So how is it gonna eat up having its receiver saturated? I'm pretty
familiar with digital comms and, with the exception of some pretty
slow speed stuff designed for weak signal work, most of it is not
very good unless you have a really solid signal-to-noise ratio.
I'm just saying that if it's getting out to my antenna that loud,
then my kilowatt is gonna have a fair chance at saturating the
thing's receiver. And the more noise they make, the more I'm apt
to have to use the kilowatt to shout over them.

Of course in our current enforcement situation here, I'd probably
simply be told to stand down and have to go to great legal lengths
to appeal the ruling.

Digital is not analog, when adverse conditions have made an analog
signal totally unusable, a digital signal, most likely, may still be
achieving 100% error free data transfer--it is just the nature of
the beast.

Actually, I've found that, except for very slow data rate stuff,
digital signals require a BETTER signal-to-noise than analog to be
readable. And there is no partial readability with most of the
commercially-used digital modes. That is to say you either have
error-free transmission or none whatever.

The "intelligence" of the software controlling the data
transmission(s) is the single most important factor--as logic would
dictate. Even under almost total saturation (it would be virtually
impossible for 100% saturation, baring hooking the kw+ rig directly
to the power lines) of the BPL signal some type of heterodyne would
be occurring with the KW signal. Since digital is simply detecting
an ON/OFF signal, in conjunction with spacing/length of these, an
on/off signal is still detectable in this heterodyne--given the
software is aware and capable of reading this signal and switching
"modes" to do so, no harm is done to the data ... and without doubt,
new error correction methods will also develop as BPL grows and
hf-rf-terrorist-hams challenge this system ... LOL!

You cannot recover data with a modem whose input transistor is biased
off by rectified RF. I know this. I've tried it.

Digital is magnitudes more robust than analog, again owing to the
very nature of the beast and the simplicity of the on/off, pulse
width, timing nature of the signal.

The only real advantage digital has is its error-correction
algorithms. Those can do very good work when they actually have
enough data to work with. But once the data recovery by the the very
ANALOG device that is receiving the signals drops below their
threshold, then the recovery becomes terrible. Some modems are
better than others. My old Telebit 19.2K could suck 1200 baud
recovery out of a phone line you couldn't talk on. But give it a
couple of volts of RF in the mix and it would drop stone cold dead.
And BPL has the "disadvantage" of not being able to filter our
frequencies AND use them at the same time. At worst, I'd drive the
BPL machinery to other parts of the band from where I was working....



Obviously, we have NOT seen the same equip/software/algorithms and
successes ... dream on ...

Algorithms will only help you by slowing down and using redundancy or by
being frequency agile and thereby clearng off my frequency. And NO
equipment DESIGNED to be a sensitive receiver at the frequencies you want
to use will be immune to even stronger signals picked up by the open
ANTENNA that you're using for a "transmission cable."

Dream on.

Look, I don't want to tell you how to engineer. But you've obviously got
your mind made up and the facts and experience of others be damned.


--
Dave Oldridge+
ICQ 1800667

BPL strikes another win ...
 

Dave Oldridge wrote:

...

This thread is beginning to switch gears, now we seem to be on the
subject of jamming; jamming is obviously possible. A simple 100 MW
white noise generator driving my KW+ lab amp would tear up a good chunk
of my neighborhood, given the right ant/circumstances. Heck, I would
probably even be placing enough of a signal on the phone lines to slow
up 56K dialup modems also.

Somehow, I just wouldn't get anything out of it. And, given the few
active hams in the US, the logic of logistics says, "moot point."

But, for those egos imagining themselves special, deserving and
empowered above mere mortals--they are allowed to dream. ROFLOL!

However, it appears the world according to you will end up with
laws/rules/regulations being passed to halt amateurs jamming of citizens
use of the internet. With as much damage as some amateurs have done to
the hobby and image of amateurs in general--I guess it won't matter too
much.

Regards,
JS

BPL strikes another win ...
 

Dave Platt wrote:
In article ,
Jim Lux wrote:


I would venture to say that with today's technology, one should be able
to get within 0.5dB of the Shannon limit without too much trouble. So,
since a BPLish signal can be many MHz wide, and the putative interfering
signal is going to be pretty narrow band in comparison, they can code
around it.


For a relatively weak interfering signal, that's probably true.

That's not likely to be the case in a lot of situations, though. A
strong interfering signal - say, a few watts of HF coming from a wire
antenna, a few houses away from a BPL receiver - is likely to be
strong enough to saturate the RF front-end of the BPL receiver. This
will result in a severe "de-sense" problem - it'll wipe out most other
signals within the receiver passband.

Ham (and other narrow-band) HF receivers deal with this problem by
limiting their receiver passband. Single-band filters prior to the
first mixer or first RF amp will keep out interferers outside that one
band, and narrow-bandwidth multi-pole filters after the first mixer
can reduce the impact of interfers that are closer to the desired
signal.

This approach doesn't work with systems which have a "wide-open"
broad-bandwidth front end, such as a typical BPL receiver, as the
receiver's front end *has* to be left open to the entire bandwidth of
the desired incoming signal. Many modern ham HTs have similar
problems... their "DC to daylight" front ends are easily desensed, or
driven into severe intermodulation by nearby VHF transmitters (e.g.
police, fire, paging, and so forth).

I imagine it's possible to reduce the severity of a BPL receiver's
desense problems by using a wide-dynamic-range front end... but these
take more power and aren't as suitable for large-scale chip
integration, and are thus going to be more expensive to build.

You can do pretty well these days.. Consider if you're using a direct
conversion receiver using a mux driven by quadrature clocks into a low
pass filter like the SDR1000.. it has fairly good out of band strong
signal rejection. Granted, in band, the performance is limited by the
following audio stages.

There's also a variety of receiver designs intended for GPS in a strong
signal environment that avoid desensing, while still retaining wideband
receive for the desired signal.

One can also do adaptive analog cancellation.

I would imagine that first (and second) generation clunky BPL receivers
would have all sort of problems, but the wide open receiver with strong
interferer problem is such a prevalent one, they'll have to come up with
a solution that fits in their price bracket.

(or, they won't, because they don't really need BPL to actually work..
They just have to keep the BPL industry alive, and speculative future
performance might be enough for that...)

BPL strikes another win ...
 

Dave Oldridge wrote:
...

http://pr-gb.com/index.php?option=co...281&It emid=9

http://www.bpltoday.com/public/1212.cfm?affID=prgb1

Regards,
JS

BPL strikes another win ...
 

Dave Oldridge wrote:

...
Algorithms will only help you by slowing down and using redundancy or by
being frequency agile and thereby clearng off my frequency. And NO
equipment DESIGNED to be a sensitive receiver at the frequencies you want
to use will be immune to even stronger signals picked up by the open
ANTENNA that you're using for a "transmission cable."

Dream on.

Look, I don't want to tell you how to engineer. But you've obviously got
your mind made up and the facts and experience of others be damned.


My son, in florida, contracts to supply firmware for these modems ...
advise all you wish; I will continue to make your posts available to
him. grin

Regards,
JS

BPL strikes another win ...
 

Michael Coslo writes:

Owen Duffy wrote:
Good grief. The answer is to power them with DC, and tell 'em
that it will serve as a magnet, thereby allowing magnetism's great
healing properties. Could sell little boxes with diodes in them. Maybe
a crystal or two for harmonic hegemony and celestial peace too.... ;^)

And do remember that a ham antanna doesn't 'radiate'. It 'emanates
energies'.

73
LA4RT Jon

BPL strikes another win ...
 

Jon ?Q?K=C3=A5re?= Hellan wrote in
:

Michael Coslo writes:

Owen Duffy wrote:
Good grief. The answer is to power them with DC, and tell 'em
that it will serve as a magnet, thereby allowing magnetism's great
healing properties. Could sell little boxes with diodes in them. Maybe
a crystal or two for harmonic hegemony and celestial peace too.... ;^)

And do remember that a ham antanna doesn't 'radiate'. It 'emanates
energies'.

73
LA4RT Jon

LA4RT Jon,

I wrote no such thing, you have misquoted, you are a fraud.

Owen

BPL strikes another win ...
 

Owen Duffy writes:

Jon ?Q?K=C3=A5re?= Hellan wrote in
:

Michael Coslo writes:

Owen Duffy wrote:
Good grief. The answer is to power them with DC, and tell 'em
that it will serve as a magnet, thereby allowing magnetism's great
healing properties. Could sell little boxes with diodes in them. Maybe
a crystal or two for harmonic hegemony and celestial peace too.... ;^)

And do remember that a ham antanna doesn't 'radiate'. It 'emanates
energies'.

73
LA4RT Jon

LA4RT Jon,

I wrote no such thing, you have misquoted, you are a fraud.

Owen

Sorry. I didn't notice that I cut everything you wrote, but left your
name in.

Jon

BPL strikes another win ...
 

Dave Oldridge wrote:

Algorithms will only help you by slowing down and using redundancy or by
being frequency agile and thereby clearng off my frequency. And NO
equipment DESIGNED to be a sensitive receiver at the frequencies you want
to use will be immune to even stronger signals picked up by the open
ANTENNA that you're using for a "transmission cable."


Good point, Dave. Any error correction comes with the expense of time,
and of course slows down the transmission of the data. The packet
doesn't jibe, so it is asked for again, and again, and so on. Better be
a heck of a algorithim when the interfering signal is really strong as
to swamp the modem's reciever.

There are plenty of examples to the contrary of the digital signal as
robust entity. Experiments have been made in which a 5 watt signal in a
car with a mobile antenna will knock out nearby BPL signals. 100 watts
in a car will do even more damage, and a base station yet more. Other
experiments have shown the so called notches being abandoned after the
system was unable to send good packets. Kind of like it was getting
desperate almost.

Seeing as how qrp levels into inefficient antennas can cause problems,
I have to wonder what will happen during the next sunspot max.

The whole BPL affair makes me kind of wonder why shielding was invented.

And for what? a DSL speed "broadband" digital signal? BPL is a poor
solution to the problems of ten years ago. It is the 8-track of
broadband access.


- 73 de Mike KB3EIA -