In comments (also attached below) filed on October 12 with the FCC, ARRL reiterated its case that the FCC should impose a 2.8 kHz limit on symbol rate for digital modes, arguing that its approach is both balanced and necessary. ARRL had asked the FCC to change the Part 97 rules to delete the symbol rate limits in §97.307(f) and replace them with a maximum bandwidth for data emissions of 2.8 kHz on amateur frequencies below 29.7 MHz. In a July Notice of Proposed Rule Making (NPRM) in WT Docket 16-239, the FCC proposed to eliminate the current baud rate limitations for data emissions, consistent with ARRL’s Petition, but it declined to propose a bandwidth limitation for data emissions in the MF and HF bands to replace the baud rate limitations.
ARRL told the FCC in its comments that the current HF symbol rate “speed limit” reflects 1980s technology and has no place in an experimental radio service in which modern protocols could be efficiently deployed in crowded RTTY/data subbands.
“The symbol rate limit was created in order to maximize the efficient use and reuse of that crowded, shared spectrum, but the assumptions made at the time are no longer valid,” ARRL said, “and the rules now prohibit radio amateurs from utilizing state-of-the-art technology, thus precluding or substantially inhibiting any meaningful contribution to the advancement of the radio art in this area.” ARRL said earlier assumptions are no longer valid mainly because there is no correlation between the data rate and the occupied bandwidth in the rules now.
The League said present rules in the HF data subbands promote inefficiency, allowing data transmissions of unlimited bandwidth as long as the symbol rate is sufficiently low, and it stressed that there must be some limit on occupied bandwidth for HF data emissions.
“Eliminating the symbol rate limitations for data emissions and substituting a maximum authorized bandwidth would permit the utilization of all HF data transmission protocols presently legal in the Amateur Radio Service, as well as state-of-the-art protocols that fall within the authorized bandwidth,” the League said.
ARRL said that it could be “fairly debated” whether or not 2.8 kHz is the proper maximum bandwidth for data emissions. “Greater bandwidth for data emissions would permit a wider array of data emissions now and in the future,” the League said in its comments. “However, even 2.8 kHz could arguably permit usurpation of the subbands to the detriment of CW and other narrow-bandwidth emissions. ARRL views the 2.8 kHz maximum bandwidth proposal for data emissions at HF to be a necessary component of the [FCC’s proposal], and it fairly balances the objectives of facilitating use of new and future data emissions and protecting against usurpation of the band by a few data stations.
ARRL said it would be impossible to reduce the permitted maximum bandwidth for data emissions at HF much below 2.8 kHz without prohibiting data modes that are now legal. “At the same time, it would not be desirable to have a few data stations using large swaths of spectrum to the detriment of other modes,” the League said.
The deadline to file reply comments in the proceeding — ie, comments on comments already filed — is November 10,