BPL: No Shortage of Critics > This makes no difference

This makes no difference

Some salient points here.
Why is BPL being pushed? Not so much because it is the best technology to get high speed data communication to the masses but because the power companies can push it as a way to create more business for themselves by jumping into this hot-technology field with as little cost or system upgrading as possible.

On the surface, who would argue with low-cost broadband access to all. But, the costs of an ineffective or problematic system needs to be evaluated. This article looks at the damage to (and from) amateur radio. Again, on the surface, most folks could care less- but amateur radio is a MAJOR communications backbone for national defense, disasters, etc.

The disruption of communications for amateur radio are also problems in many radio communication systems currently used in defense, aeronautics, etc. Because BPL will rely on a wide signal through spread-spectrum frequency use, it cannot simply be notched out or attenuated with RF (radio frequency) filters.

There are now many US private and governmental agencies, some military and public service that have rallied against the damaging effects of BPL technologies. In most cases this is not based on fear of the unknown, but actual testing done at and around the BPL test sites across the country.

Further substantiating these concerns are the trials done in other countries prior to BPL even taking much interest here in the US. As mentioned in the article, in other countries such as cutting-edge technology loving Japan, BPL was discarded due to the detrimental effects to various radio services. Other European countries have scrapped BPL after their own research showed indelible damage to many (some critical) radio frequency based services.

Presently, there are many complaints against electric companies for lossy power lines, bad transformers, insulators, etc...causing RF interference through arcing and RF radiation. It has often been an uphill battle for complaints to be resolved. Yet, on these (some leaky and antiquated) systems, the power companies want to inject powerful large radio-spectrum BPL signals.

Personally, I have no beef against the power authorities, however the proposed systems are worrisome. It would be great to offer broadband to those who cannot easily get it, but in this case the messenger (form of delivery) may need to be shot. There are less invasive means that should be considered.

said by KB2PSM:

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The disruption of communications for amateur radio are also problems in many radio communication systems currently used in defense, aeronautics, etc. Because BPL will rely on a wide signal through spread-spectrum frequency use, it cannot simply be notched out or attenuated with RF (radio frequency) filters.

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There are a number of different techniques used in access BPL, from spread spectrum to OFDM (multi-carrier signals). With most of the technology being presented, this rapidly changing wide carrier has generated "noise" over several radio bands all at once. Basically, the systems being tested have wide signals over several large bandwidths simultaneously. Most radio transmitters and receivers use a small sliver of spectrum or specific frequencies such that the frequencies just above and below can be sharply attenuated or dissipated. With these multi-carrier signals that basically stretch from frequencies between 2 and 80 MHz, BPL could affect HF and low-VHF allocations wherever it's deployed and such a wide active frequency range precludes any use of filters on either the BPL or radio receiver end.

Here are a few Amateur Radio inspired links on BPL:
»www.arrl.org/tis/info/HTML/plc/
»gullfoss2.fcc.gov/prod/ecfs/retr···15383154

Here are some video and audio streams of some of the actual tests conducted both in the US and abroad-
»www.arrl.org/tis/info/HTML/plc/#Video

Be well,
Rob

Wouldn't they have to be pumping out a huge amount of power to have significant impact on a full 78MHz of frequency? (I'm not completely familiar with how wide a carrier a HAM radio would use but it must be infinitesimal by comparison to something 78MHz wide.)

said by AthlGrond:

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Wouldn't they have to be pumping out a huge amount of power to have significant impact on a full 78MHz of frequency? (I'm not completely familiar with how wide a carrier a HAM radio would use but it must be infinitesimal by comparison to something 78MHz wide.)

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reply to AthlGrond
Its not so much that a huge amount of power will be required to create the interference as much as the proximity to the signal. An overseas signal can be rather weak, yet still clearly received by the receiver. A very weak, but local and all-encompassing signal sweeping the same frequency will easily obliterate any others.

The output power of a signal is not the de-facto reason for its reception. Simplifying things- Relative to the receiving station, it is the signal that has the greatest "Field Strength" that will be heard. A tiny signal in the "near field" can easily eliminate extremely powerful signals coming from further away.

Perhaps a fair analogy would be the use of an earphone. Although the volume of the earphone might be minute, the proximity to the ear drum can effectively drone out much louder, yet further noises.

We often look at radio frequency power levels on a relative level, such as a station transmitting 1000 watts should be received more strongly than a 1 watt transmitter. To put this in perspective, when received they excite the receiver in levels of dBmW. By the time, or depending on the condition that the 1000w signal traveled to the receiver, it can present much less dBmW than a much closer yet extremely weak signal.

Where BPL makes a mess of things is in its near-field. Since most radio operations will occur around areas in which power lines are in proximity, these receivers will be easily overloaded with strong signals and interference. Given a "leaky" power line, transformer or poor insulators, the problem only increases.

I hope that I haven't been too simple- I am trying to avoid being too technical.

Rob

What I was thinking is that if BPL were broadcasting at say 1000W of power between 2 and 80MHz the average power output would be .000013W/Hz . Do I have this part of the BPL noise generation wrong?

My understanding was that there is a noise floor that you have to overcome with any carrier wave transmission. Wouldn't this just add a tiny bit to that noise? Or are the power levels that you are dealing with just so small that even a little noise can mess the lot up?

Thanks for your replies BTW

reply to rf_engineer
Does the signal strength seen by HAM of the BPL not get reduced by the spectrum spreading? Or is it a matter of not enough reduction?

said by AthlGrond:

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Does the signal strength seen by HAM of the BPL not get reduced by the spectrum spreading? Or is it a matter of not enough reduction?

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reply to AthlGrond

said by AthlGrond:

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My understanding was that there is a noise floor that you have to overcome with any carrier wave transmission. Wouldn't this just add a tiny bit to that noise? Or are the power levels that you are dealing with just so small that even a little noise can mess the lot up?

Thanks for your replies BTW

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reply to rf_engineer

Direct Sequence

Frequency Hop

said by rf_engineer:

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said by AthlGrond:

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Does the signal strength seen by HAM of the BPL not get reduced by the spectrum spreading? Or is it a matter of not enough reduction?

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Kinda sorta not really With spread spectrum the signal or carrier has to be somewhere in the frequency spectrum at any given moment. Any carrier needs to be strong enough to be above the noise floor, overcome transmission losses, and be received. So there is a minimum signal level required for any given carrier being emitted at any given moment. The signal isn't on every frequency at every moment, so the average power over time observed on one frequency is lower, but the peak level is still there.

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said by rf_engineer:

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But looking at this from a BPL design point of view independent of the modulation technique, one would want to run as high a power level as physically and legally possible as this would decrease the need for repeaters, increase the range, and make the system more cost effective. This limit for emissions is 30uV/m at 30 meters. This would apply to any signal regardless of the modulation technique. While some modulation techniques may squeeze more effective bandwidth out of a chunk of spectrum, the raw emission level is still there.

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The sensitivity of most amateur and many shortwave receivers is on the order of .5uV. That means that even with a very modest antenna, a 30uV/M field will clearly swamp out desired signals. Since most of us live within 30 meters of a powerline, such a field will be a very effective jammer.

said by N0JCG:

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The sensitivity of most amateur and many shortwave receivers is on the order of .5uV. That means that even with a very modest antenna, a 30uV/M field will clearly swamp out desired signals. Since most of us live within 30 meters of a powerline, such a field will be a very effective jammer.

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FCC Part 15, the regulation the BPL falls under, allows 30uV/meter. Part 15 was written to cover unlicensed, localized and intermittent applications, like garage door openers and early cordless phones. An occasional blip from a nearby garage door opener at 30uV/meter would be heard on a receiver, but it would only be there for a fraction of a second very infrequently; hence not a problem. BPL, however, would be radiating at the max 30uV/meter virtually continuously; big problem!
For a graphic video of what this is like see;
»216.167.96.120/BPL_Trial-web.mpg - for those with broadband access
Internet: »216.167.96.120/BPL_Trial-small.mpg - for those with slower access

said by N0JCG:

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FCC Part 15, the regulation the BPL falls under, allows 30uV/meter. Part 15 was written to cover unlicensed, localized and intermittent applications, like garage door openers and early cordless phones. An occasional blip from a nearby garage door opener at 30uV/meter would be heard on a receiver, but it would only be there for a fraction of a second very infrequently; hence not a problem. BPL, however, would be radiating at the max 30uV/meter virtually continuously; big problem!

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They could specify reduced emissions, but then BPL won't work at all because the signal has to get down the power line itself a sufficient distance to make the whole thing economical. The FCC could just as easily allow the current limit and tell everyone else to just live with it. What is more likely is they will leave the limits as is. In that case we will have to insist on strict enforcement of the second half of Part 15; that a Part 15 device must cease operation if it causes harmful interference and must accept whatever interference it receives. We already know that a nearby HF transmitter can reduce the BPL bit rate to zero. The BPL providers will have to live with that and advise their users that the service can be interrupted at any time.

reply to AthlGrond
Another recent update-
found on www.eham.net, borrowed from the ARRL Letter:

Organizations' Comments Augment Alarm Over BPL:
from The ARRL Letter, Vol 23, No 01
Website: »www.arrl.org/ on January 3, 2004
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Organizations' Comments Augment Alarm Over BPL:
Two organizations have filed comments with the FCC that augment previously expressed worries about potential interference from and to Broadband over Power Line (BPL) systems. Picking up on the "grave concerns" the Federal Emergency Management Agency (FEMA) »www.fema.gov expressed over BPL December 4, the nonprofit Disaster Preparedness and Emergency Response Association (DERA) »www.disasters.org called on the FCC to require impartial BPL field testing as well as additional public comment and full and open public hearings.

"DERA concludes that serious interference to and disruption of critical emergency communications systems in several licensed services throughout North America would almost certainly result from BPL implementation as currently proposed," DERA said. Endorsing the earlier FEMA remarks, DERA said proposed BPL systems don't just pose a risk of interference, they've already been shown to "actually cause harmful interference to licensed radio services."

Meanwhile, the Amateur Radio Research and Development Corporation (AMRAD) has filed additional test data with the FCC to support preliminary findings suggesting that BPL systems are susceptible to interference from even modest Amateur Radio HF signals. AMRAD said its newest data demonstrated that amateur operation in the test neighborhood would cause many homes to lose their Internet service.

"At least an area out to a radius of 0.51 miles from the transmitting station could have their Internet connection interrupted," AMRAD said. "Closer-in homes would almost certainly have their Internet service interrupted."

For its RF susceptibility experiment, AMRAD used the Potomac Electric Power Company system test site. It features a mid-1960s vintage home with unshielded interior electrical wiring and overhead power lines.

AMRAD found that at a distance of just over one-half mile, data transfer ceased in the face of a 100-W signal on 3980 kHz from a mobile transmitter. Adjacent to the test property, AMRAD said data transfer ceased in all but one instance at a transmitter power of just 4 W in the BPL operating band of from 4 to 21 MHz.

The ARRL hopes to complete an independent BPL engineering study early this year. It will explore how BPL might affect HF and low-VHF amateur operation as well as how Amateur Radio operation could affect BPL systems.

In related news, BPL equipment manufacturer Amperion Inc recently announced an "industry first" by successfully testing its high-speed "Connect" system on 69 kV transmission lines. Typical BPL systems have employed medium and low-voltage lines to deliver broadband and Internet access. Amperion said its tests, performed in conjunction with American Electric Power, demonstrated multi-megabit data transmission to a distance of nearly one mile without the need for a repeater. There's more information on Amperion's Web site »www.amperion.com/press.asp?pid=89.

Additional information about BPL and Amateur Radio is on the ARRL Web site »www.arrl.org/tis/info/HTML/plc/. To support the League's efforts in this area, visit the ARRL's secure BPL Web site »www.arrl.org/forms/development/d···ons/bpl/.

Source:

The ARRL Letter Vol. 23, No. 01 January 2, 2004

Austria is the next country to walk away from BPL