October 12, 2016-The American Radio Relay League is expressing concern about a notice of proposed rulemaking adopted by the FCC recently. In the NPRM, the FCC proposed “to remove limitations on the symbol rate (also known as baud rate)—the rate at which the carrier waveform amplitude, frequency, and/or phase is varied to transmit information—applicable to data emissions in certain amateur bands.”
The Commission said “that this rule change will allow amateur service licensees to use modern digital emissions, thereby better fulfilling the purposes of the amateur service and enhancing its usefulness.” The NPRM was adopted in response to a 2013 petition for rulemaking filed by ARRL.
In comments filed yesterday in WT docket 16-239, ARRL noted that the NPRM “proposes – per ARRL’s Petition – to remove limitations on the symbol rate applicable to data emissions in certain amateur bands. Notably, however, and most problematically, the Notice does not propose to implement the very necessary, additional rule change proposed by ARRL, which is the establishment of a bandwidth limit on the order of 2.8 kilohertz for Amateur data emissions in the RTTY/data subbands below 29.7 MHz.”
The group said it proposed a 2.8 kilohertz bandwidth limitation because there isn’t currently a “bandwidth limitation for data emissions in the band segments where data emissions are permitted (with the exception of rules which limit unattended operations which were not affected whatsoever by ARRL’s Petition)” and “[t]he symbol rate limit does not now act as a bandwidth limitation for HF data emissions.”
The filing added, “An occupied bandwidth limit of 2.8 kilohertz is wide enough that it will permit to continue those data emissions currently permitted by the existing rules, and it will permit additional data emissions that are now prohibited because the symbol rate limit of 300 baud applicable to the HF bands below 28 MHz precludes them. At the same time, a 2.8 kilohertz bandwidth limit is sufficiently narrow that it limits the ability of any given Amateur station using data emissions of that bandwidth or less to usurp overly large portions of the limited, crowded and shared RTTY/data subbands.
“Some opponents of the ARRL Petition argued that their non-data operations would suffer if the proposed rule changes were adopted,” ARRL noted. “However, they offered no evidence that the relief proposed in the ARRL Petition would create a situation in which data transmissions will overwhelm the subband, precluding narrow bandwidth emission communications. In any case, ARRL argued, a bandwidth limit much lower than 2.8 kilohertz would have the effect of precluding those data emissions that are already in constructive use in the RTTY/data subbands now. To those few who argued that it is necessary to continue a completely outdated regulatory restriction that has no relevance to modern data communications as a primary means of avoiding interference to CW, RTTY or narrower-bandwidth data emissions such as PSK-31, ARRL simply disagreed. The Commission has properly chastised the Amateur Service for resisting deregulatory proposals that are designed to enable Amateur experimenters to refine and adapt technologies. ARRL is of the view that outdated Commission regulations that needlessly preclude experimentation with data technologies should not be preserved as an alternative to cooperative sharing arrangements in the HF bands through voluntary band plans, coupled with some minimal ‘traffic laws’ that are necessary to ensure equitable and compatible sharing in very limited spectrum.”
ARRL added, “Notwithstanding any of the foregoing, those who either opposed deletion of the symbol rate limit or supported that deletion but opposed the ARRL’s proposed 2.8 kilohertz maximum bandwidth for locally and remotely controlled data emissions in the MF and HF bands have a very valid concern that absolutely must be addressed. They collectively express a predictive, unquantified fear that an increase in the number of data emissions in the RTTY/data subbands will create new incompatibility between data emissions and ongoing CW, RTTY and narrow bandwidth data modes (such as PSK-31) that are and have long been popular in the low ends of MF and HF bands. This concern must be addressed.”
A number of individual amateur radio operators also filed comments. For example, W. Lee McVey said, “While there is a demonstrated need to eliminate the existing constraint on data communication symbol rate in the Amateur Service, in so doing, there is a clear and present danger in not specifying a maximum emission bandwidth. It has been observed that transient bandwidth characteristics of certain data codes employing Orthogonal Frequency Division Multiplexing (OFDM) can suddenly obliterate ongoing adjacent communications without warning. Also, unauthorized, unspecified digital data codes (UC)s are in use on the high frequency (HF) amateur bands. I believe that these concerns justify further consideration in this, or yet another, Rulemaking Proceeding.”
“The FCC should recognize the important ramifications of this ruling, as it will impact the ability of the hundreds of thousands of narrowband operators to continue to enjoy the hobby if unlimited baud rate, unlimited bandwidth signals are allowed to operate in the same spectrum currently used by narrowband amateur operators,” said Ted Rappaport, a professor-electrical engineering at New York University and an amateur radio operator. “An unlimited bandwidth signal with unlimited baud rate will essentially allow wide walls of digital signals with arbitrarily large bandwidth to ride roughshod over narrowband signals. The FCC’s NPRM was silent on the issue of interference, and should provide some governmental regulation to avoid the potentially disastrous situation where a regulatory framework would legally allow interference by unlimited bandwidth signal.” – Paul Kirby, firstname.lastname@example.org