Courtesy of the ARRL Newsletter:
The Information Systems Technology group, part of the North Atlantic Treaty Organization's (NATO) Research and Technology Organization (RTO), released their report, "HF Interference, Procedures and Tools" (RTO-TR-IST-050), in June. This report "address[es] the concerns raised by the potential for unintentional radio interference to be caused by the widespread operation of broadband wire-line telecommunications systems."
BPL, also called Power Line Telecommunications (PLT) in Europe, uses existing power lines for telecommunications with data rates higher than 1 MBit per second. NATO said that since existing power lines were not designed for such transmissions, "they will cause unintentional RF emissions which may adversely affect the established radio noise floor directly, or by cumulative propagation from many such sources. The
existing HF background noise possibly may be increased via ground wave and/or sky wave propagation."
Not only could this be a problem for Amateur Radio operators, but NATO said that military users would be affected as well: "Increase of the existing HF noise floor by widespread use of PLT...will bring up problems for Military Radio Users as well as for HF Communication Intelligence (COMINT) in all NATO countries. The signal-to-noise ratio thus may be reduced for tactical and strategic HF radio as well as for
fixed sensitive COMINT sites."
Saying that "PLT will produce the most problems regarding HF interference,"the report makes the assertion that ambient noise levels in Europe have not increased in the last 30 years. This was proved using measurements made by the ITU in the 1970s compared with noise levels today, with the report saying that the "ITU Recommendations for natural and man-made noise in the HF-range are still valid in Europe."
The NATO report said "[r]ecent measurements carried out in Germany and Great Britain indicated that there is no remarkable difference between these measurements, specifically no increase of the ambient noise in quiet rural zones within the last 30 years. Based on these measurement results, the cumulative interference field strengths far away from telecommunication networks should not be higher than -15 dBuV/m (9 kHz bandwidth) across the entire HF range, if no measurable increase in
minimum noise levels are to be tolerated."
Conversely, some European PLT proponents "in presentations and discussions have argued (without being able to prove it) that ITU recommendations based on measurements carried out in the 1970s are no longer valid, as the man-made and the ambient noise levels have increased since that time to considerable higher values (by up to 30 dB)."
The NATO report also indicated the following: A high probability that PLT would cause increased noise levels at sensitive receiver sites given the projected market penetration; and the percentages are highly influenced by assumptions on transmitter EIRP (equivalent, or effective, isotropic radiated power), PLT market penetration and duty cycle.
ARRL Laboratory Manager Ed Hare, W1RFI, was pleased to see the report. "The findings described in this paper are based on good science. NATO has concluded that protection levels well below 0 dBuV/m are needed to prevent interference to sensitive HF operation. They studied distance extrapolation and concluded that 40 dB/decade is not the correct factor to use to make measurements at one distance, and related the measured values to other distances. They also have advanced the state of the art and determined that the aggregate noise from large scale deployment of
BPL will increase worldwide noise levels by skywave propagation."
Hare points out that NATO's report "pretty much echoes the ARRL's pleadings during the BPL rulemaking." The ARRL has constantly argued against the 40 dB/decade extrapolation factor that, while recommended by the FCC, the report found, "was not confirmed by measurements carried out by other organizations."
The report acknowledges that there are no commonly accepted regulatory emission limits from PLT and recommends that countries work together to limit these emissions. "While it is highly desirable that the regulatory limits on PLT emissions be harmonized throughout the NATO countries, the RTG recognizes that NATO, by itself, has no regulatory authority over the emission limits. Therefore, it is recommended that NATO seek the implementation of this goal by working together with the national and international regulatory authorities."
The full report, "HF Interference, Procedures and Tools," can be downloaded in pdf format at http://ftp.rta.nato.int/public/PubFullText/RTO/TR/RTO-TR-IST-050/$$TR-IST-050-ALL.pdf.
