Broadband over powerlines ( BPL)

Here's an article I found on the subject.

Lets think about this from a power stand point before we panic. In order for BPL radiation to be a significant problem to us those power lines need to radiate at least 100 mw in each of our RC bands per mile of power line. From what I have read BPL will radiate over a total bandwidth of in excess of 50 MHZ. This means that if the radiation is a problem to RC the total radiation per mile of power line will exceed

500 watts. Think about how many miles of power lines there are. With this kind of radiation loss the lost electricity costs start to mount for the power company. Worse, at this kind of radiation loss there will have to be a pretty good amplifier every few miles of power line. The capitol costs of all those amplifiers should sink the project on the drawing board.

The only reasonable thing to conclude is for the grossly insensitive Rx we use BPL simply will not put out enough power to stop us from flying. You think our Rx are not insensitive? Well, to take an extreme example NASA sends readable signals half way across the solar system with Tx power output in the same range our RC Tx put out. Sure they use huge, high gain antennas and lots of signal processing. But the fact remains our Rx are crap for sensitivity compared to lots of other types of Rx. We do not pay much for our Rx and we do not get much in return.

That is not to say that radiation levels far below what I have talked about above would not shut down many other types of applications. Ham radio operators deal with far, far lower signal levels then we deal with for instance. Any appeal to AMA is useless. I doubt much if they have anyone on the staff with the slightest qualifications in radio signal transmission and reception. How can they appeal when they do not know anything about the topic? About all they can do is make mud in the water and cause other users who have real problems to lose impact with the appropriate agencys.

Crying wolf over this problem when we are tiny users and amoung the least likely to be impacted does not get anyone anyplace I fear.

There are for sure several people on this newsgroup better qualified to respond to the original query then I am I suspect. So why are the guys with degrees in EE who fly not worried? I think the silence from them says there is no problem for us.

Actual physical testing by highly qualified professionals working primarily in the Ham radio bands have documented the problem as real.

It does not take a 100mw transmitter to lock out your 100 mw transmitter, a lot less will do it. Note that all of the power lines better radiators that our short, ground level rc transmitters.

Fortunatly, the same technology that leaks out will also leak in. If the BPL plan is put into place, I don't think it will be a big job to simply hijack the system for free service.

Bear >> As you may or not know this system has been cited by almost all radio/tv

| > As you may or not know this system has been cited by almost all | > radio/tv services as asevere interference causer in the | > near?future .AARL has come out against it . Any comments from the | > AMA frequency commitee???

I believe the AMA has stated that they're investigating.

| Lets think about this from a power stand point before we panic. In | order for BPL radiation to be a significant problem to us those | power lines need to radiate at least 100 mw in each of our RC bands | per mile of power line. From what I have read BPL will radiate over | a total bandwidth of in excess of 50 MHZ. This means that if the | radiation is a problem to RC the total radiation per mile of power | line will exceed 500 watts.

Your reasoning is interesting, but flawed.

Assuming you've got a very long power line -- several miles long at least. Since it's running BPL, we've got another name for it -- it's also an antenna.

As long as your distance from the antenna, er, power line is much less than the total length (you're in the near-field), the RF field power from it will drop off at 1/r -- where the RF field power from our own transmitter drops off at 1/r^2 once you get out of the near-field (20 feet should be more than enough.)

Assuming that you're using FM, your receiver will basically pick up whichever signal is stronger. But with your signal dropping off at

1/r^2, and the BPL signal dropping off at only 1/r, once your plane gets something like 1000 feet from you or more, the RF from the BPL may begin to dominate even though you may still be 1000 feet from the power line too. The exact point where you lose control will depend on the actual emissions from the power line, which I do not know.

Also note that a signal does not have to be exactly in your channel bandwidth (10 kHz) to cause problems. Outside of that, it should be filtered out, but it'll still desense your receiver, making your transmitter signal seem weaker than it would otherwise. And don't neglect the possiblity of things like intermod causing problem.

As for 500 watts/mile, to the power company, 500 watts is nothing. These lines probably lose much much more than 500 watts/mile strictly due the resistance of the wire. 500 watts would cost me as a consumer about $0.05/hour, or about $1/day, and if that mile of power line allows the power company to offer BPL to 20 people, they've already recouped the loss many times over.

| Think about how many miles of power lines there are.

Not all power lines need to carry BPL data. It looks like many implementations even have the power lines being used to carry the signal to WiFi hotpoints up on the power poles, which are used to actually bring the data inside the houses.

| With this kind of radiation loss the lost electricity costs start to | mount for the power company. Worse, at this kind of radiation loss | there will have to be a pretty good amplifier every few miles of | power line.

Yes, there will have to be a pretty good amplifier every few miles of power line. If you go to a place where they're trying out BPL you can even see the amplifiers now.

| The capitol costs of all those amplifiers should sink the project on | the drawing board.

BPL is a bad idea for many reasons, and the RF noise it creates is not the only one.

| The only reasonable thing to conclude is for the grossly insensitive | Rx we use BPL simply will not put out enough power to stop us from | flying. You think our Rx are not insensitive? Well, to take an | extreme example NASA sends readable signals half way across the solar | system with Tx power output in the same range our RC Tx put out. Sure | they use huge, high gain antennas and lots of signal processing.

Do not discount the benefits of huge, high gain antennas and lots of signal processing. And I believe that Voyager transmits with about 13 watts of power, and I think the transmitting atenna has 48 dB of gain, and the receiving antennas have 74 dB -- there's LOTS of gain here, so this isn't a very good comparison.

is interesting reading.)

| the fact remains our Rx are crap for sensitivity compared to lots of | other types of Rx. We do not pay much for our Rx and we do not get | much in return.

That's true. So they're also likely to be affected by intermod and other things that could be caused by BPL.

| Any appeal to AMA is useless. I doubt much if they have anyone on | the staff with the slightest qualifications in radio signal | transmission and reception. How can they appeal when they do not | know anything about the topic?

That's hardly fair. Lots of AMA members are hams (myself included) and I know Dave Brown is (though that doesn't mean he knows anything about this.) If the AMA needs technical expertese and doesn't have it in-house (which is merely conjecture on your part), they can easily hire an expert, or the ARRL will probably help provide what they need if they just ask.

| Crying wolf over this problem when we are tiny users and amoung the | least likely to be impacted does not get anyone anyplace I fear. | | There are for sure several people on this newsgroup better qualified | to respond to the original query then I am I suspect. So why are the | guys with degrees in EE who fly not worried? I think the silence from | them says there is no problem for us.

I've got a degree in physics and one in astronomy. I also dabble in ham radio. I know something of what I speak, and I have mentioned it here before (though I was saying that `the sky may or may not be falling' rather than `the sky is not falling' (like you are) or `the sky is falling' (like the guy I responded to.)

BPL *will* affect our radio systems -- that's clear. But it's not clear how much it'll affect them. If you keep your plane close in, and don't fly right next to the power lines, you're probably fine. But if you fly it half a mile away, a few hundred feet above a long power line running BPL ... you may very well have a problem.

Some real world testing is needed, and I hope that the AMA is doing so now. If they can't do it themselves (which I doubt), the ARRL would probably be more than happy to help.

Apparantly the AMA has done at least a little with this --

though it certainly doesn't look like they've done much.

I was a bit amused by this passage in the pdf file --

The AMA is a 175,000 member national association representing aeromodeling activities ... further the membership also includes approximately 10,000 licensed amateur radio operators who pilot model aircraft, predominately on 50 MHz frequencies.

Do the AMA members who are also hams really `predominately' use the 50 mHz frequencies to fly their planes? I do use them, but only occasionally, and I've seen nothing to indicate that lots of R/C ham users use the 50 mHz band for R/C activities at all.

Thanks Doug. Your response is very well reasoned and logical. As a Ham for over 50 years, plus an engineer in research til retirement, etc. I am also concerned over this BPL mess. I admit I fear the risks can be great, especially in a large scale event near a metropolitan area, where one plane caused to crash by the BPL leakage can destroy our sport. Incidentally, the world's most advanced electronics nation, Japan, has examined the issue and denied any further work on BPL. Seems like our experts ought to talk to theirs.

And I have some equipment for flying on 50 MHz, but generally just use the 72 MHz channels.

Olin McDaniel, W4PFZ

To reply by email, please remove "abcd" from Return address

----------------------------------------------------- "Ignorance is treatable, Stupidity is incurable. Sometimes the difference is hardly distinguishable, however."

I thought I might have taken care of these factors when I picked 100mw per mile in channel. After all, our Rx are tuned to only pick up about 1/3 of the channel. At least the better Rx do this. Maybe not the elcheapos used in some park flyers? According to the FMA lit they even have a Rx which will operate when a second Tx is turned on useing exactly the same channel. So I guess I am not convince you are correct Doug. But then I am not convinced you are not convinced either.

In terms of your statement "assuming that you're using FM" none of us use FM. Our Tx that are called FM are actually sending frequency shift keyed signals. Does this have an impact on what the Rx picks up?

Yes, and this costs the power company some $150,000 a day in lost power assuming the amplifiers are 100% efficient. This kind of loss is not insignificant, even to a large company. In towns and citys a mile of line might get to a lot more consumers then 20. In rural areas a lot less. And most of the miles of line are rural. So perhaps this BPL interference is only a problem if you live in a city as rural areas will not be covered?

| I thought I might have taken care of these factors when I picked 100mw | per mile in channel. After all, our Rx are tuned to only pick up | about 1/3 of the channel.

1/3rd of 10 kHz? 3.3 kHz? No, I think they pick up more than that, probably double that.

| At least the better Rx do this. Maybe not the elcheapos used in | some park flyers?

Probably not. I know the Hitec Feather has been known to have problems with R/C people on adjacent channels, and they're 20 kHz away (in the US.) And intermod seems to hit them hard too.

| According to the FMA lit they even have a Rx which will operate when | a second Tx is turned on useing exactly the same channel.

Yes, I've heard of these. I don't believe the hype.

Well, you could make it work under certain conditions, even without special receivers, but I don't believe that a special receiver can make this work all the time.

| So I guess I am not convince you are correct Doug. But then I am | not convinced you are not convinced either.

I'm not even convinced I understand what you're trying to say! :)

Am I convinced that BPL is a big problem for R/C use? No. Am I convinced that BPL is not a big problem for R/C use? No. Am I convinced that BPL is a big problem for ham use? Yes.

BPL will raise the noise floor. That much is obvious. But exactly how much, and how much will that affect us, that remains to be seen.

| In terms of your statement "assuming that you're using FM" none of us | use FM. Our Tx that are called FM are actually sending frequency | shift keyed signals. Does this have an impact on what the Rx picks | up?

Yes, I'm familiar with how the signal looks. And I can listen to it just fine when I put my scanner in FM mode (as opposed to AM, SSB or CW modes.) If you really care about the specifics, you can read about them at

but for my purposes here, FM R/C equipment is FM.

Specially, I'm talking about the capture effect. FM receivers (like the ones most of use use, and this includes PCM) tend to pick up the strongest signal and ignore the weaker signals.

On the other hand, AM (and SSB, CW, etc.) signals do not do this, and a weaker signal will be received along with the stronger signal. So where a FM setup may work fine with a slightly weaker noise source somewhere nearby, AM may not be so lucky.

| > Also note that a signal does not have to be exactly in your channel | > bandwidth (10 kHz) to cause problems. Outside of that, it should be | > filtered out, but it'll still desense your receiver, making your | > transmitter signal seem weaker than it would otherwise. And don't | > neglect the possiblity of things like intermod causing problem.

And don't ignore this. A signal does not have to be right on your channel to cause problems. 500 watts/mile may be way more than is needed.

| > As for 500 watts/mile, to the power company, 500 watts is nothing. | > These lines probably lose much much more than 500 watts/mile strictly | > due the resistance of the wire. 500 watts would cost me as a consumer | > about $0.05/hour, or about $1/day, and if that mile of power line | > allows the power company to offer BPL to 20 people, they've already | > recouped the loss many times over. | | Yes, and this costs the power company some $150,000 a day in lost | power assuming the amplifiers are 100% efficient.

... and assuming 150,000 miles of wires with BPL, and assuming 500 watts/mile. Lots of assumptions here.

| This kind of loss is not insignificant, even to a large company.

Of course not. But we still don't know if this is actually the dollar loss, or just a figure that bears little resemblence to reality.

| In towns and citys a mile of line might get to a lot more consumers | then 20. In rural areas a lot less. And most of the miles of line | are rural. So perhaps this BPL interference is only a problem if | you live in a city as rural areas will not be covered?

Perhaps. Though I think BPL's big promise was to reach rural customers (though there's a big gap between what was promised and reality.)

That is a big smoke screen as far as I am concerned and I am rural. 7 miles from the CO and can't have DSL or cable. My options now are satellite or wireless. I don't believe the power company is going to install the BPL repeaters that would be required to provide service to me.

How many remember bubble memory of about 30 years ago? It was a memory technology had large storage that was not cost effective. By the time it got cost effective normal RAM was more cost effective.

I hope that wireless will take off and make BPL totally ineffective. The wireless access just became available for me.

It appears that this is precisely what is happening. 8>)

Ed Cregger

Wireless has some serious drawbacks of its own. Biggest of which is security!

People will eventually become used to the idea that there really is no security when it comes to electronic data/communications. I have. It no longer bothers me.

I do not store anything on my computer that I am not willing to share with the world.

I do not worry about someone else gaining access to my credit card information because I carefully choose credit cards that protect my interests as best as possible.

Identity theft is a reality that will probably strike most of us during our life times. We need to enhance laws protecting we citizens from the consequences of identity theft. Not hide from thieves. Conversely, we need to stiffen the penalties for performing such deeds.

Ed Cregger

Agreed. There are plenty of things you can do to minimize the risk but thinking that you are immune is a fantasy.

I do several things because of what others report. Such as making sure my PayPal credit card account never has more than a couple hundred dollars in it. Setting my daily limit on my debit cards to only a couple hundred dollars authorized (this worked great after a scanned card in Spain).

What Ed said exactly

Tomb

Doug,

I did this experiment several years ago. I heard the tone on my FM Rx just like you do. Would you care to conjecture as to why we hear this tone on an FM Rx and what its waveform might look like? Or perhaps one of the other electronic gurus on the newsgroup can explain it? TNP, you claim a lot of electronic knowledge. Care to respond?

| I did this experiment several years ago. I heard the tone on my FM Rx | just like you do. Would you care to conjecture as to why we hear this | tone on an FM Rx and what its waveform might look like?

We hear that sound on a FM receiver because that's the signal that's sent. You'd hear the same sound if you took the buddy box signal and ran it into a speaker as well.

If you were to put the audio signal into an oscilliscope, you'd see it jumping back and forth between no voltage and full voltage -- pulses, if you will. There's a 2 ms `off' period, and then a number of pulses sent. The length of the pulse indicates the position of the servo for that channel, with channel one sent first, then 2, then 3, etc. up to

2. The reason that people say `AM is not AM' and `FM is not FM' is that yes, the transmitter is AM or FM, but the signal fed into it is binary

-- on or off. So the resulting RF signal probably looks more like morse code, either on or off, for AM and the FM signal probably looks more like frequency shift keying -- bouncing between two slightly different signals.

There are several pages about this online if you just google for it ... or if you have an osciliscope, run your buddy box output into it and see for yourself.