Technical Topics, August 2003
NASWA Alerts FCC To BPL Danger
For the first time in its long history, NASWA has publicly defended the interests of shortwave broadcast listeners in the USA. On June 30, 2003 NASWA submitted an 18-page filing to the FCC in response to Notice of Inquiry 03-104 concerning Broadband Power Line (BPL) communications. The Journal does not have the room to print the entire submission, but this month I will attempt to summarize many of the points made in that submission. Comments by AMRAD and the NAB also mentioned the impact to shortwave listeners and I have included part of their comments too.
As you probably already know from the Musings in the June NASWA Journal, there are well-funded interests who want to use the commercial power lines as a way to conduct high-speed data communications. Many of the proponents of this technology have chosen to design systems using frequencies that are between 2 and 30 MHz.
The number of shortwave listeners in the USA is hard to estimate accurately since Arbitron does not survey such listeners. The CIA Factbook says there are 575 million radios here. If only one percent of these radios have shortwave capability, that would be almost 6 million shortwave receivers. A reasonable estimate would be that hundreds of thousands of listeners tune in to shortwave broadcasts weekly.
As wonderful as enhanced broadband competition could be for improving our access to information, the use of free-to-air shortwave radio broadcasts by hundreds of thousands of weekly listeners is a right that must be protected by the FCC.
Shortwave broadcasts are accessible to even the poorest people for a one-time equipment cost of less than $150. In its efforts to expand subscription-supported broadband Internet access, the Commission must not force economically deprived persons to incur monthly subscription costs or purchase a relatively high-cost interface device, such as a computer, to access information available today for free. A free democratic society depends on free access to information in order to have an informed electorate. The effective exercise of democracy demands that all persons have an inherent right to inform themselves regardless of economic status. The FCC must, therefore, protect the public interest by protecting existing methods of access to free information.
Shortwave broadcasts are accessible to even the poorest people for a one-time equipment cost of less than $150. In its efforts to expand subscription-supported broadband Internet access, the Commission must not force economically deprived persons to incur monthly subscription costs or purchase a relatively high-cost interface device, such as a computer, to access information available today for free. A free democratic society depends on free access to information in order to have an informed electorate. The effective exercise of democracy demands that all persons have an inherent right to inform themselves regardless of economic status. The FCC must, therefore, protect the public interest by protecting existing methods of access to free information.
BPL systems must protect the internationally allocated frequency bands between 5.5 and 26 MHz that are used by international broadcasters to reach listeners in the USA. (If the FCC desires to adopt a standard that will be marketable in foreign countries, attention must also be directed to internationally allocated bands between 2.0 and 5.5 MHz which are in use for both domestic and international broadcasting in many parts of the world.)
Notches in the BPL spectrum have been proposed to protect various licensed radio services. It is dangerous to carve out holes in the allowable radiated spectrum from BPL devices because that will forever constrain the flexibility the ITU and the FCC have in adjusting the HF broadcast bands to accommodate changing needs. Once the BPL physical plant is widely deployed, the cost of modifying the plant to accommodate new broadcast frequency allocations will be prohibitive. Frequencies used by international broadcasters between 2.0 and 26 MHz are defined and allocated by the International Telecommunications Union (ITU) through its periodic World Administrative Radio Conferences. These allocations are somewhat dynamic and have been expanded over the years to accommodate the growing needs of broadcasters and listeners.
NASWA recommends the spectral region between 30 and 47 MHz be considered. Users are declining in this frequency range as public safety and law enforcement services migrate to 800 MHz trunked systems.
This migration to higher frequencies is being spurred by the increased need for liaison between emergency response agencies. Effective homeland security also requires protecting law enforcement communications from eavesdroppers. Digital trunked systems in the 800 MHz range improve both interoperability between agencies and secure communications from casual eavesdroppers.
The US military also uses frequencies in the 30–47 MHz range for mobile communications. These communications are not normally connected to or in proximity to residential power distribution lines. Joint use of these frequencies should be possible. Additional testing is recommended to verify this assumption. Alternatively, the communications signals should transition to fiber-optic technology at the distribution transformer secondary.
The presence of high-pass filters to facilitate bypassing of distribution transformers will inevitably cause an increase in unwanted interference conducted and/or radiated from the medium voltage wires of the power distribution network and the low voltage wiring in the home.
These transformers normally act to limit propagation of such noise components. Noise components originating in homes tend to be confined to the homes connected in parallel at the secondary winding of the distribution transformer. High Frequency (HF) noise components developed upstream of the distribution transformer are inhibited from reaching residential customers by the reactance presented by the transformer at HF frequencies. Bypassing these transformers at HF frequencies will allow the high voltage distribution network to propagate the interference components both out of the home to the medium voltage distribution network and in the reverse direction from sources well beyond the immediate vicinity of the home user of shortwave radio broadcasts.
The interference emitted by the neighbor’s drill, even if it exceeds Part 15 limits for incidental radiators, might be tolerable because the drill is used only infrequently. The BPL devices will be on continuously. To the deleterious effect of such a device in one’s own home must be added the cumulative effect of all the BPL devices in neighbor’s homes that share the same secondary winding of the distribution transformer.
Real-world tests and demonstrations are currently being conducted by power utilities. The FCC should require such field trials to qualitatively measure the interference experienced by receivers such as the YB-400 operating with its attached whip antenna in such an environment. Just as the Food and Drug Administration requires manufacturers of new drugs to prove they are both effective and safe, the FCC must put the burden of proof on manufacturers of BPL systems to show they will not inhibit access to international radio broadcasts in typical listening environments. Of course one way to eliminate such a strenuous burden of proof would be to confine all such systems to the 30 to 47 MHz part of the spectrum.
Tests have been conducted by the HomePlug® Alliance and the American Radio Relay League to measure the effect of simulated HomePlug® devices on reception in the HF spectrum in real-world homes with external HF antennas. The bottom line results show that with a 30 dB reduction of radiated components in the amateur radio band frequencies, compared to levels permitted by Part 15 regulations, the effects could be reduced to almost inaudible levels as long as the receive antenna was located 10 meters or more from the house wiring. The report is available on the Internet at:
This frequency avoidance approach used in the above tests to protect the amateur radio service does not protect the HF broadcast bands that are the concern of NASWA. A few data points taken in the referenced tests in specific HF broadcast bands showed noise floors were raised as much as 14 dB when the HomePlug® device was turned on. The effect on receivers with built-in antennas in close proximity to house wiring is expected to be much greater. The FCC uses a scaling factor of 40 dB when transferring measurements made at 3 meters distance to the 30 meter distance specified in Part 15 rules. That would imply at least 40 dB of additional protection is necessary in order not to interfere with reception of international HF broadcasts on receivers with attached antennas in the home, and near house wiring.
If 70 dB (30 dB from the HomePlug®/ARRL tests plus 40 dB of additional protection due to receive antenna proximity to the house wiring) of protection were to be afforded to the HF broadcast bands, there is a serious question whether there would be enough spectrum left for HomePlug® products to achieve commercially competitive data rates.
The NASWA submission then directed the FCC to test reports from Europe and Japan, available on the Internet, which show the measured interference to radio communications services by equivalent technology.
The standards for interference must be tightened over those that presently apply to Part 15 devices. When Part 15 regulations were established decades ago, people who desired to listen to foreign broadcasts on the HF spectrum typically erected outside wire antennas which could be given sufficient physical spacing from power lines to avoid interference from conductive and radiation fields on both power lines and house wiring. These big antennas were required because the broadcast stations typically ran only 50 kW and the vacuum tube receivers of the day were noisier than today’s solid-state designs.
Current local government and restrictive deed regulations often do not provide the HF listener any way to use an outside antenna. Outside receiving antennas are prohibited by most modern restrictive covenants and many zoning ordinances for residential communities. (No relief was given to HF radio listeners when the FCC ordered reasonable accommodation for amateur radio service antennas in local zoning processes and the FCC did not pre-empt restrictive covenants that banned outside antennas when the Commission took such action for TV and Direct Broadcast Satellite antennas.)
A modern Grundig, Sangean, or Sony “shortwave” radio has sufficient sensitivity to hear signals near the atmospheric noise floor using small, attached-whip antennas more often than not located within a few meters of house wiring. Any BPL solution must specify radiated and conducted interference limits that recognize the performance of modern receivers and the way they are used by most listeners. Receivers with noise floors in the neighborhood of 1 microvolt across 50 ohms in a 5 kHz bandwidth are typical for the better portable radios with “shortwave” capability. Moving the BPL frequencies to the band between 30 and 47 MHz will greatly reduce the interference mitigation techniques that would otherwise be required to protect HF broadcast reception.
Both radiated emission limits and conducted emission limits should be controlled by FCC regulation. Because the wires are unshielded, currents conducted in the wires will radiate. How much they radiate is not under the control of the BPL device manufacturer nor the BPL service provider.
The wires are already in the wall or on top of the ceiling. What is there is there and only the building owner can legally change that. Houses built in the last few decades universally use unshielded Romex type wiring in place of the older BX type metal sheathed cables which were common in the 1950’s and earlier. The Romex style cable being unshielded will radiate and there is nothing the homeowner can do short of ripping out the house wiring and replacing it with grounded, shielded cable. Such an alternative will logically cause the homeowner to opt for the more economically attractive cable modem or DSL approaches for broadband access. BPL could die before it ever gets off the ground unless the FCC limits conducted and radiated emission levels. Moving the BPL spectrum to 30 to 47 MHz will help the FCC to specify less stringent limits.
Any system that is marketed on a worldwide basis must protect the rights of billions of people who only have shortwave radio to bring them the truth. The FCC must understand that in many parts of the world, where local despotic governments control the only local radio stations, listeners use shortwave radios to hear the truth from international sources. Today some people risk their lives to hear international broadcasters delivering the real news of the world and home country events. The United States Government devotes hundreds of millions of dollars each year to such broadcasting.
Wouldn’t it be ironic if “Made In The USA” BPL devices, allowing access only to internet sites that the local dictator approved of, were the very cause of interference that prohibited oppressed peoples from hearing these shortwave transmissions?
Any system deployed in the USA will likely be aggressively marketed overseas. Our system must, therefore, also protect foreign shortwave listeners’ rights to hear the truth unencumbered by local government restrictions. That will not only be in the interest of the US Government but also in the interest of all the world’s citizens who value freedom and aspire to more democratic societies.
As a final word of caution, NASWA suggested that the FCC consider the potential hazards that might result from failure of transformer by-pass devices. Power utilities will be responsible for the safety of devices they install to enable Access BPL technology. The Commission must ensure that transformer by-pass devices, used for Access BPL applications, cannot fail in a way that might place thousands of volts (from the medium voltage distribution network) on home wiring and devices. Consumers must be assured that this technology is safe if Access BPL is to find wide acceptance. Protective schemes, such as fuses, must be proven to act fast enough to prevent electrocution or equipment damage for all possible failure modes.
Other organizations besides NASWA filed comments that also noted the danger to broadcast reception. This comment is from AMRAD, the Amateur Radio Research and Development Organization:
“AMRAD performed testing in Potomac, Maryland and found that the test BPLinstallation radiated signals in the HF band but the signal design avoided radio amateur allocated bands with the exception of the new 5 MHz frequencies. The BPL signals radiated were impulsive and sporadic, with bursts correlated with packet transfers. The density of the pulses are expected to increase with the number of active users of the internet in the neighborhood. The radiation bands were centered on 5, 9 and 11 MHz which nominally correspond to international shortwave bands. This installation used the high voltage lines to distribute the BPL signals and used only a single wire, which causes radiation. No attempt was evident in this installation to drive the power lines as a balanced line to reduce the unintended radiation and hence, significant radiation was observed. This installation turns the overhead power line into an effective center-fed dipole extending for hundreds of feet in either direction.”
The National Association of Broadcasters also had comments that address and support NASWA’s concerns. “BPL experimental licensees have made only passing references to “no reports of interference” but have not supplied measurement data to support those assertions. A lack of consumer complaints is woefully inadequate evidence upon which to base any conclusion that BPL does not cause interference.
“It is uncommon for a viewer to complain to the FCC or the broadcaster when interference occurs. Faced with a poor broadcast signal or no signal at all, a viewer is likely to respond only by switching the television channel.
“Further, it is highly unlikely that television viewers would even be aware that the entity holding an experimental authorization caused interference to their television receiver. Assuming, arguendo, that a consumer could identify the source of interference and lodged a complaint to the broadcast licensee, the broadcaster could not modify the consumer’s television receiver to address the interference problem. Instead, the broadcaster would have to rely on a lengthy process at the Commission level to (1) determine and confirm the source of interference and (2) require the BPL entity to correct the interference.”
So it is clear that the battle lines have been drawn. It will be interesting to see how the FCC handles the interference issue. NASWA intends to submit additional reply comments before the August 6 deadline. The NTIA has not weighed in yet but they are concerned about interference to government spectrum users. NASWA will keep you informed via the Journal as developments occur.
The NASWA Executive Council would be interested to hear your reaction to this new role that NASWA has undertaken. Do you approve or do you think such representation is outside NASWA’s charter? Send your comments to the Executive Director at the postal or e-mail address on the top of page 1. Pro or con, your opinions count. Until next time, stay tuned.