ARRL Raises Concern About 2.3 GHz Interference
Amateur radio operators use frequencies near 2304 MHz for long distance, narrow-band communications. This part of the 2300-2310 MHz amateur radio band has even been used to bounce signals off of the moon for distant communications. As may be expected, amateur radio operators are very concerned about interference to their weak signal communications in this band.
As previously reported, the Report and Order in WT Docket Number 07-293, published in the Federal Register on Aug. 3, 2010, amended the rules for the Wireless Communications Services in the 2.3 GHz band to permit mobile broadband services in addition to fixed services in the 2305-2317.5 and 2347.5-2360 MHz bands.
The FCC claimed the rule changes do not risk harmful interference to neighboring operations, specifically satellite radio, aeronautical mobile telemetry and deep-space network operations. The Amateur Radio Service was not included in the FCC's list of protected services.
On September 1, the American Radio Relay League, representing Amateur Radio operators, filed a Petition for Clarification or Partial Reconsideration. The ARRL requested that the FCC affirm:
- •That Section 2.102(f) of the Commission's rules applies to Wireless Communications Service (WCS) fixed and mobile operations, so that harmful interference that is caused to Amateur Radio Service operations in the 2300-2305 MHz band is to be remedied by WCS licensees.
- •That the current out-of-band emission (OOBE) limits for WCS devices set forth at Section 27.53(a)(3) of the Commission's rules continue to apply to mobile, portable and fixed facilities across the entirety of the 2300-2305 MHz band following the rule changes implemented in this Order.
The 2300-2305 MHz portion of the amateur band is not shared domestically with any other service.
"This type of operation has proven over time to be completely compatible with deep-space research and other operations below 2300 MHz, and the ambient noise levels in the 2300-2305 MHz band are historically very low, making the band attractive for amateur weak-signal communications, the principal amateur use," the ARRL stated.
The organization explained that "it must be assumed that mobile broadband devices will proliferate at and above 2305 MHz following the R&O and that they will be operated in close geographic proximity to amateur stations operating in the 2300-2305 MHz band."
The FCC had dismissed potential interference to amateur radio operations at 2304 MHz in a footnote 405 of the R&O, noting that out-of-band emissions from WCS—when expanded to permit mobile broadband and portable devices at up to 250 mW EIRP—could have an effect on amateur operations in that band.
The Commission said that "some amateur stations operating around 2304 MHz may experience an increased antenna noise temperature caused by the implementation of mobile WCS operations, and will have to tolerate this change in the RF environment." It added that the technical flexibility allowed to amateur stations in Part 97 of FCC rules may allow operators of these amateur stations "to offset or mitigate the effects of this change" by relocating or redirecting antennas or "by making other permitted technical adjustments."
Broadcasters, who have followed the FCC's proposal for reclaiming additional television spectrum, will appreciate the ARRL's comment on the FCC's "cavalier dismissal" of their concerns. The ARRL states that this action represents "the latest in a series of instances in the past few years in which the Commission has made unwarranted and completely incorrect assumptions about the ability of amateur radio stations to avoid preclusive interference from an incompatible spectrum use by reorienting or relocating antennas."
This tracks along the lines of the FCC's refusal to acknowledge comments from respected engineers about the potential for interference to off-air television delivery in the Commission's latest broadcast television spectrum reclamation effort.
The ARRL noted that that in the case of the 2.3 GHz encroachment, "those assumptions are made without any factual basis at all, in order to justify an allocation decision the Commission desires to make."
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Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.