There are a growing number of BPL trials taking place in the United States. ARRL HQ staff have been involved in a few of them that are within driving distance from Connecticut, but local contact is often more effective in dealing with local utility companies, so in areas where local amateurs are willing to work with their electric utility companies, this local contact is the first point of contact to assess the interference aspects of BPL.
Single Point of Contact
ARRL is ready and willing to help these volunteers in any way it can. A single point of contact is needed, however, so a local amateur has to be ready to step forward and assume this role. He or she interfaces with HQ staff and helps coordinate local contact with the local utility company, the BPL-equipment manufacturer and other local hams to determine what cooperation is available and appropriate. (In some cases, the point-of-contact function can be a small group of individuals.) Although this local liaison needs to be able to understand the technical issues, the ability to work productively and calmly with the parties involved, even when there could be large differences of opinion and position with respect to BPL and the interference potential to amateur radio, is more important. Other local hams may be able to help with mobile receivers to take to the trial areas and by documenting the levels of noise at their stations before and after testing commences.
The following steps are a guideline. The exact process that can or should be followed in any given area depends a lot on the level of cooperation offered by the utility and the availability and skills of the local hams who are going to pitch in.
- Determine local talent
- ARRL may already know a lot about your system. Check the BPL database file ARRL maintains. If you can fill in any blanks or if you see any errors, please contact Ed Hare (W1RFI) at ARRL HQ.
- Contact your electric utility and establish a good line of communication. If you can, determine location and dates of the trials or BPL installation
- Determine BPL manufacturer
- Determine what BPL equipment is being used in the system and what frequencies it uses
- Report this information to Ed Hare (W1RFI).If the system isn’t in place yet, make measurements of pre-system noise. These can be field-strength or S-meter measurements. You are establishing a baseline so that you can document any change in noise levels.
- Work with your power company as appropriate. The intent is to determine if they are using amateur spectrum in any way and to demonstrate to them any interference that occurs. Their reasons for cooperating are different than ours, but there is still common ground and value in working with them.
- Determine whether there are amateurs in or near the trial areas. Unfortunately, in these small trials, it can be hard to find those active hams. But interference to mobile stations is just as much interference as to fixed stations, and, in a small trial, if you don't have stations in the trial area, it is a reasonable alternative to bring stations to the area. Duquesne wants to learn about BPL, and they need to evaluate that in the context of what will happen if they build it bigger. And don't discount inactive or VHF-only hams. You may well find that some are willing to help anyway, especially if 6 meters is affected. In Feeding Hills, MA, a VHF-only Tech was most interested in helping. We had to loan him some equipment, but once we did, interference reports came from him. He also filed an 11-meter report. Even a VHF-only ham could be listening to WWV, W1AW or other code practice or international shortwave broadcasting. Interference to any of these signals is also reportable.
- Amateurs within a few miles of the trial area should follow the steps in the complaints instructions and report any BPL interference to the utility, with copies to the FCC as described in the document.
- The most persuasive RFI reports will come from amateurs at their home stations. Some trials are small, however, and there is a probability that there are no amateurs in a particular trial neighborhood. In that case, mobile receivers brought into the trial area and to assess interference show exactly what will happen if that system expands in scope. It also shows what will happen to mobile stations that do try to operate from anywhere that BPL system is deployed.
- This testing should also be done to supplement any reports of harmful interference from home stations.Periodic reports to Ed Hare (W1RFI), should be sent, as needed and appropriate. Ed is also a resource that can offer advice at any stage during the process.
The Major Parties Involved in BPL
The following information explains the different perspectives of the major parties that you may need to contact and work with. There are at least two and possibly three interested parties in field trials.
One is the utility that owns the lines. They are looking at BPL as a possible revenue stream and also as a possible way of remotely reading meters remotely or controlling equipment. But they are generally open to evidence that BPL will be more of a headache than it's worth to them. Those that work for a utility are often being asked by their management to make an informed recommendation about whether getting involved in BPL will be profitable for their company. For that reason, many utilities very much want to learn as much as they can about all sides of the interference problem.
The BPL manufacturer has a different perspective. They want to sell their hardware and they have a powerful incentive to minimize the interference issue. They probably will have cultivated close personal relationships with the utility folks prior to the public announcement of the test, which puts us at an initial disadvantage with the utilities. Amateurs will have to work to overcome that.
There may be a third: a broadband service provider such as Earthlink. They're interested in is in expanding their customer base. They're likely to regard interference FROM BPL as someone else's problem. If amateur radio can help show them the problem of interference TO BPL they will take notice, because they'll be the ones dealing with the unhappy customers who have unreliable service.
Once you get a BPL team organized, contact Ed Hare (W1RFI) with the name, call sign and email address of those active in your BPL team. He will add them to the firstname.lastname@example.org reflector, a list ARRL created to let the BPL groups across the country talk with each other. The participants on this list typically the general and technical leaders of the group. Any and all who are actively involved with their local BPL team are welcome on this relector.
Where Should the Interference Bar Be Set?
Where the bar should be set is an important concept. It simply is not reasonable to expect that limits (regulatory or voluntary) could be set at a level that will never cause harmful interference. There are three important goals here:
- To have BPL operate at a level on various parts of spectrum that will reduce the occurrence of harmful interference to a low-enough incidence that it is practical to resolve interference on a case-by-case basis
- To have solutions at hand that can be applied on a case-by-case basis
- To have a strong commitment from BPL manufacturers and operators that they will apply those solutions to whatever extent is necessary to address interference.
ARRL has been doing its best to help the BPL industry come to terms with the first criteria. A few BPL companies have taken EMC very seriously. Others have not. In all cases, in order to protect amateur radio, they will have to operate at a lower level much lower than Part 15 in the Amateur bands in order to prevent widespread interference. In its filings on the NPRM, ARRL put on the plate that to protect mobile operation, the suppression of emissions in the amateur bands should be 40 dB, but in no case less than 30 dB.
Those levels are achievable. Motorola, for example, has additional filtering on its products to reduce the signal levels in the Amateur bands. Current Technologies and IBEC, two BPL manufacturers, ave system designs that do not put signals below 30 MHz on overhead power lines. The modems they use below 30 MHz are notched in the Amateur bands, operating under the HomePlug specification. Experience in their deployments shows that this generally protects mobile stations and many fixed stations. Fixed stations in RF quiet areas, however, still have a risk of interference. So do WWV and the reception of international shortwave broadcast stations. But in general, if the BPL being deployed in your area is one of these companies, you can expect fewer interference problems -- or none at all on the Amateur bands. Although you should be cautious in your optimism, it is important for you to know that these companies address EMC better than the others as you plan your interaction with your power company.
The rules are clear:
- BPL must not exceed the maximum emissions limits
- BPL must avoid locally used spectrum
- BPL must correct harmful interference promptly, on a mutually agreed upon schedule
Under the FCC’s rules, in addition to meeting the emissions limits described below, the operators of BPL systems must not cause harmful interference. Harmful interference is defined in the FCC’s rules:
Harmful interference. Interference which endangers the functioning of a radionavigation service or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radiocommunication service operating in accordance with the Radio Regulations. (FCC Rules, §97.3(a)(23))
This definition does not just apply to the Amateur Radio Service. It originates in the Constitution of the International Telecommunication Union (ITU) and is faithfully reproduced in the international Radio Regulations as well as in the general rules and regulations (Part 2) of the FCC Rules.
In some cases, there has been considerable disagreement between licensed radio users and BPL operators about whether noise heard on a band is “harmful interference.” While noise that is present for a very brief duration, or noise that is a single birdie on a band, may not always be harmful interference, BPL occupies tens of MHz of spectrum, all of the time. The Part-15 limits will typically result in S9+ level signals to mobile and fixed Amateur operation, along as much as a mile of overhead power line from a single BPL device connected to that line. That’s harmful interference by any definition.
In some cases, the BPL operator or manufacturer may argue that because there are no fixed Amateurs in a small deployment area, radio operators should just drive away. This argument is flawed for a number of reasons. First, the rules don’t require licensed users to “drive away,” and unlicensed users are not given the authority to give permission to licensed users as to what type of operating they can do. Equally important to the involved electric utility, if they are undertaking a small trial to learn what will happen if they spend many millions of dollars to build a larger system, they need to treat the small deployment in a way that shows them whether they can correct interference problems on a larger scale.
One important thing that is learned from these trials is how well interference can be prevented, and mitigated if it happened. These small installations should be treated the same way as they will be if BPL were installed in your entire service area, because if this goes as planned, sooner rather than later, it will be installed near a fixed station that requires more protection than would be needed for a mobile station. If at this trial stage, the "solution" is to claim that what is reported isn't really interference, it will not be possible to determine what can be done in cases where that claim cannot be the solution.
It is not usually practical, nor necessary, for hams to make actual measurements to know whether a BPL system is exceeding the limits or not. In general, it takes a calibrated loop antenna or biconincal dipole (depending on frequency) and a spectrum analyzer with CISPR quasi-peak detection and bandwidth to make field strength measurements. If you have such equipment, it can sometimes be a plus to use it, but don’t get trapped into thinking that only measurements can be used to document interference. To the contrary, BPL signals that cover up even weaker signals you are trying to use are harmful interference, and the industry has no cause to even argue about the levels that have been reported by hams in most systems.
S meters and mobile antennas aren’t really accurate, but in general, a “legal” BPL signal of 30 uV/m at 30 m distance from the source would be S0+25 dB or so to a mobile whip antenna mounted on a vehicle driving or parked on the road, preamplifier off with an SSB bandwidth receiver. Levels significantly above this may be indicative that the system is exceeding the limits.
Information on making measurements is posted online.
Notching is a term that BPL has coined to describe their turning off carriers to limit the BPL signals in spectrum they want to protect locally. In general, the depth of these notches is about 25 dB. If a “legal” BPL signal is S9+25 dB, and there is 25 dB of notching, this would still be an S9 signal. This is clearly strong harmful interference to Amateur Radio. (Motorola has improved their notches with hardware filtering). It has been ARRL’s experience that those companies that operate below 30 MHz on overhead lines do not have sufficient protection in their notches to protect Amateur Radio. We see several types of notching problems:
o Insufficient notching, with a significant amount of additional noise added to the local noise level
o Notching that tries to protect an Amateur band, but that misses and operates at full strength in part of one or more bands.
o Poor rolloff at the notch edges, resulting in insufficient notching at the band edges, improving as one tunes into the band
Although not as bad as “full legal limit” BPL, these notching problems can and do cause interference to fixed and mobile stations along significant distances along power lines.
If you can bring a mobile station to the area, park it across the street from power lines and give a listen to the bands. First, listen outside the ham bands, in spectrum that the BPL system is using. It will probably be loud. Then, tune into the ham bands. If they have put in sufficient guard bands near their notching, the ham bands could be clean. If you listen in the AM mode, BPL has a sound that once heard is distinctive. Check each band edge carefully. If they are clean, that's great news. You can pack it up and go home, and explain to them why it is critical that they continue the notching in the ham bands as they deploy a larger system. Do point out that in some cases, BPL manufacturers have been able to notch a small system, but not able to do so in a larger deployment. The utility should be certain that they are getting full value from their smaller trial, so they should be ensuring that the BPL company can continue the notching in a larger system. The HomePlug companies can, as the notching is fixed in their design. These include Current Technologies; IBEC and Motorola.
Those companies operate only with HomePlug modems that operate only from premise wiring. They are also quiet except when in actual use. With this combination, even though a mobile station could encounter some noise as it were driven past a home actually using a HomePlug modem at the time to download a large file or web page, that noise would be localized to the area near the house, and it would quickly disappear. In general, a mobile Amateur station could go to an area and easily find a place to operate. This implementation generally protects mobile operation. There is still some interference potential to fixed stations, especially those in RF quiet areas. However, Current Technologies has deployed past 60,000 homes in the Cincinnati without major interference problems. Current, IBEC and Motorola have taken a design approach that should prevent most interference and they have all agreed to discuss solutions with ARRL should interference occur under other circumstances.
Avoiding Locally Used Spectrum
In residential neighborhoods, one does not know where Amateur or CB operators are, or where people are listening to international shortwave broadcast. But there are at least hundreds of thousands of those radio users out there. The only want, IMHO, to meet the goals of having a low-enough incidence of interference is to avoid the use of that spectrum in residential neighborhoods. Some manufacturers have done so, at least for Amateur Radio. Others have not, and say they will be “complaint driven,” although we have seen that in many cases, their idea of complaint-driven means to do what they can do easily, then proclaim that they have corrected all “legitimate” cases of interference. Some in this industry fully expects that Amateur Radio should live with the 15 dB or more of degradation that their present level of notching provides.
What is ironic is that with all of the posturing about avoiding interference responsibilities, the companies that are having the greatest success in the marketplace are the ones that avoid using amateur spectrum.
It can be a real judgment call as to just how “formal” to make complaints. If your utility is being very cooperative, it could be a good choice, especially in a small trial, to simply report your findings to the utility. It can, if they are really playing square, be productive to give them a bit of slack to find out for themselves just how bad BPL is. But even so, a few things things are important:
- Give them reports of any interference you are finding.
- Let them know that, even for a small trial, the nature of a "trial" is such that they need to use it to learn about the system, and learning whether they can -- or can't -- resolve interference is important. For that reason, they need to determine that they can indeed correct interference problems, then carry that over faithfully to a larger deployement
- Even if you don't have a cooperative relationship with the utility, the FCC expects that intial reports of interference should go to the utility
- In all cases, copies of reports or interference complaints should be sent to the FCC. This helps the FCC better understand BPL interference nationally and establishes a record of your interfence and the attempts (failed or successful) to fix it. Unfortunately, some BPL companies have not been forthright about interference that was reported less formally, so the FCC needs to be involved from the getgo.
- If you do report it to your utility, be clear that it must be corrected quickly, or the system shut down except for brief tests to assess interference
- Under the rules, they must resolve interference promptly, on a timetable agreed upon by you and the BPL operator. The BPL industry has told the utilities that interference can be fixed easily, so a routine case should be correctable in a matter of days, not weeks or months. Certainly, no more than a week should be agreed to for routine cases. In special circumtances, don't be unreasonable, but you need to make sure they understand that things need to move as quickly and easily as the promises.
- If they don't make their correction-date target, again, be reasonable, but firm. If there are only a few loose ends to tie up and a sincere offer to do so, that's different than if they can't make any progress, or worse, start blaming you for being unreasonable.
- Speaking of which, if they start telling you that you can't operate mobile in the area, remember that operators of unlicensed devices do not give permission to licensed users to operate their stations under the FCC's rules.
- I would also suggest that if you don't hear from them in a week, or if you are not satisfied with the way the case is being resolved, you need to file formal complaints with the FCC.
In any event, even informal complaints must be made. In too many cases, the lack of complaints early on has given a utility the impression that the claims made by the BPL manufacturer to have corrected all interference must be true. That may be true for some manufacturers or some installations, but in each case, local Amateurs should thoroughly determine that for themselves and report what is found accurately to the power company and BPL manufacturer.
Small Trials vs Larger Deployments
In some cases, especially in smaller trials, there may be no fixed stations in the BPL area. In that case, a reasonable alternative is to bring a mobile Amateur station to the area. This is a typical Amateur operation and any interference to that station is as important to fix as any other. It will also provide the BPL operator with important information.
In the case of a small trial, located in a small geographical area, the BPL industry has often taken the position that the mobile operator should just "drive away." Unfortunately, the premise that they are not causing harmful interference to a licensed user of the spectrum because the operator isn't staying away from the area where there unlicensed operation is occurring is flawed. The FCC rules on harmful interference do not specify fixed or mobile operation. The "drive-away" principle would not be applied to users of cell phones, so it should not be applied to mobile Amateur Radio operation. While hams are smart enough not to park right across from a house with a noisy device operating inside it, the premise that we can drive over a mile away to operate is not and should not be acceptable.
To put this into perspective, even though this may be a small trial, as a technical trial, it is intended to find out what problems will be encountered and what must be addressed. To that end, the BPL operator should want to have all available information about interference, so they determine now what will happen if they decide to deploy BPL in their entire system.
Although noise does exist in today's technological world, most Part-15 regulated devices (from computers to electric motors) have emissions limited in frequency, geography or time. We can often live with and work around this type of noise. For mobile stations, the principle I generally apply is that a mobile station should be able to go to an area and easily find a location from which it is possible to use any spectrum allocated to that mobile station. Moving 50 feet away from a moderate noise source may be acceptable, but having to drive around within a 1-mile radius to find a spot that works is not.
Under the rules, the operator of an unlicensed device has a requirement not to cause harmful interference. The rules do not say that it is sufficient to make interference unlikely. While doing so it a good idea, even unlikely interference must be addressed if it occurs. The only way to address interference to a mobile station is to prevent it from occurring in the first place, as it cannot be addressed after the fact. If BPL were deployed over an entire state, there would be no way that the utility could correct what would amount to hours of continued interference.
Your electric utility is the operator of that system. They are trying to decide whether they are going to deploy BPL, and if so, what BPL vendor will best suit their needs. I would focus your report to them in that light. If you operate mobile, it may be only by happenstance that you have not been to that area. Other amateurs, either those in your area or those just passing through, may have experienced interference and not known the reasons or to whom they should report it. In every sense of the word, that would have been interference that existed whether it was reported or not. It may be worth a few days to coordinate with other hams in your area, to determine if other HF-mobile Amateurs in your area may have seen interference there, or who may also want to assess the impact of this system on their operation, either in the short term, or as an indication of what will occur if they build that system out to the entire service area.
I would think that the next step could be to establish communication with your utility. How things get handled from there can very much depend on what kind of communication and cooperation they are willing to establish with you. In some cases, the BPL operator has taken a hard-line adversarial posture. In that case, it has been clear that the best recourse was for the Amateur to file formal interference complaints. In other cases, an electric utility or ISP has been very cooperative, and with an excellent dialogue and willingness to openly communicate, the best approach has been to report findings to the BPL operator and let the company learn for itself whether the interference problems can be addressed. That has to be a judgment call, but one tempered with the premise that they really must use that as a learning opportunity and really must address the interference.
Whether fixed or mobile, you should document your findings and report interference to the utility. If you do operate mobile in your general area, even if you don't normally go to the area of the BPL deployment, outline briefly that you operate HF mobile as part of your normal operating. Do explain that you did intentionally go to the area to assess its interference status. You can then describe your mobile station, the areas you visited, dates and time (approximate fine) and some description of what spectrum was impacted at a few specific locations. Those locations should be chosen to reasonably represent the scope of the problem, without being selected to overstate what is actually seen there. Above all, you want to accurately convey what their system is doing to Amateur Radio in the area and what it will do if deployed over a larger area.
Although you don't have to do a full test with sophisticated test equipment, the more "scientific method" you use in your reporting, the more credible and useful it will be. You may want to read through measurements for some general guidance, tailored more to measurements, but useful to any type of testing.
When you send your report, indicate that you want to help them learn about the EMC aspects of BPL and that you want local Amateurs to be a local resource to help them do that. Do let them know that you expect that they will use this opportunity to correct the interference problems and to find out if it is as easy as may have been indicated to them. If in the course of ongoing dialogue, you determine that they are using this as a technical trial, and not as the advance guard on a major deployment, you may want to give them more time and a bit of breathing room, although that is best done with in-person interaction. But even then, the goal needs to remain focused on correcting the problems you are reporting. Hopefully other hams in your area will have similar findings and a similar approach.
Fixing BPL has proven to be the challenge. The BPL industry uses what it has termed "notching" -- essentially turning off carriers in DSP. This has not always been a good solution, especially with overhead wires involved. The notches are 20-30 dB, and dropping an S9+ noise level by even as much as 30 dB would still be S5. I would raise this issue in the first report, indicating that experience in other systems has shown that notching has not always worked, and that if it proves to be inadequate, and interference still remains, additional solutions may be needed.
Copy the FCC on All Interference Reports and Complaints
And even in cooperative cases, it has proven to be appropriate and necessary to provide informational copies of your findings to the FCC. At this stage, the FCC is still trying to learn about BPL and what problems are being seen in its deployment. FCC is in the process of making national decisions about BPL and it is important that they learn about all problems encountered. Also, in some cases, BPL manufacturers have not always acted in the same cooperative way that some BPL operators have. In Irving, Texas, for example, Amperion and TXU terminated a test, but left the equipment on the poles. It continued to radiated "dead" carrier noise at S9+ levels, and the local hams involved continued to file complaints to TXU. ARRL got involved in that complaint, and when it was not corrected, ARRL wrote a formal FCC complaint. When the equipment was removed from the poles, the noise stopped, so ARRL and the local amateurs withdrew their complaint.
Amperion responded by claiming that it and TXU had never heard a single interference complaint, and that ARRL's complaint was made after the system had been turned off. Had the ongoing complaints been cc'ed to the FCC, they never would have been able to make that very incorrect statement. The history of all this can be seen by searching the ARRL site. Since that time, ARRL has recommended that the FCC be cc'ed on all reports that involve interference, even if they are being provided to the utility directly.
This is a specialized topic, and information on how to file complaints.
Things that electric utilities can do to minimize interference complaints
1. The 12 bands mandated in the rules
2. Amateur Radio, with guard bands as recommended by DS2
3. SW broadcast, no additional guard bands generally needed
4. Avoid 49 MHz (Baby monitor territory. Under the rules, that is not protected, but they want to avoid phone calls)
5. Locally used 30-50 MHz as appopriate (McDonalds clown no, ambulance yes)
6. Operate with state-of-the art -35 dB or better notching
7. Reduce gap noise
8. Carefully set operating levels.
a. In RF-quiet areas, operate 10 dB below FCC
b. In other areas, opeate at FCC
c. Any further reduction for special circumstances can be handled case by case
9. Implement outreach program
a. Local fire, police, ambulance
b. Local military/government
c. Local ham clubs
d. Include ARRL in outreach. ARRL will help resolve any remaining interference on a case-by-case basis
Here are some URLs that may be helpful:
Martinsville, IN BPL BLOG:
This page outlines the successes and failures encountered by the utility operating BPL in Martinsville, IN. This is must-reading for every utility considering BPL.
Pre-BPL Baseline Measurements:
To better assess the impact of BPL in a neighborhood, ARRL is soliciting baseline measurements of the present levels of man-made noise at amateur stations.
A detailed description of how to make relative measurements, baseline measurements and Part-15 measurements.
Additional Instructions for Specific Types of BPL Systems
(See also HomePlug)
Others to be added