It Seems to Us: Coexistence
As one of the oldest incumbent radio services, Amateur Radio is constantly on the defensive. We are hardly alone. Consider broadcasting, for example. After the 1947 Atlantic City Radio Conferences the bands 470-585 and 610-940 MHz were allocated exclusively to broadcasting, worldwide -- and with additional regional allocations (585-610 MHz in Region 2) to boot. With the completion of the transition to digital television this month, the frequencies in this range that remain available to US broadcasters have been whittled down to 470-608 and 614-698 MHz, with one or two 6-MHz channels in the 470-512 MHz band also used by land mobile in a number of metropolitan areas. Broadcasting has lost about half of its allocations in this valuable part of the spectrum. In addition, wireless microphones and similar low-power devices have had the use of vacant TV channels for years, and these channels -- so-called "white spaces" -- soon will be used for broadband data services as well.
The amateur service arguably has fared a bit better, although we are secondary in our three allocated bands between 420 and 1300 MHz. We lost 1215-1240 MHz in 1979 but picked up a whole new band at 902-928 MHz. These bands have other occupants, and some of them are primary. We are obliged to not interfere with the primary services and we must accept whatever interference their operations may cause to us, but we still get a lot of use out of them.
Of the three, the 420-450 MHz (70 cm) band is by far the most popular among amateurs. In a 2003 survey, half of the respondents who were active said they used the band. There are more than 8,000 FM, digital and television repeaters operating on 70 cm, along with simplex FM, satellite, and weak signal operators using CW, SSB and a variety of digital modes.
Historically we have managed to coexist with military radars, although recent upgrades to the Pave Paws installation at Beale AFB have created some issues for repeater operators in northern California. Wind profiler radars, which beam straight up to measure wind speed and direction as a function of time and altitude, were engineered into the upper 2 MHz of the band several years ago and will be coming on line as NOAA funding permits. The federal government also operates a secure spread spectrum network, the Enhanced Position Location Reporting System (EPLRS), in the band.
The 420-450 MHz band has been a popular target for a variety of unlicensed, low-power devices. As a licensed service we enjoy priority over them, so while they can be a nuisance (particularly when the devices are designed for use in Europe or elsewhere and do not conform to the FCC regulations) they have not posed too much of a regulatory threat. When a regulatory threat does arise, normally we can count on being joined in opposition by the federal agencies that also use the band.
Not every proposed use of the 420-450 MHz poses an equal threat. We already share the band, and some potential sharing partners are more compatible than others. A compatible sharing partner may actually strengthen our position against subsequent proposals.
We should consider a current FCC rulemaking proceeding, ET Docket No. 09-36, in that light. In response to a petition filed by the Alfred Mann Foundation, a leading medical research organization, the FCC is seeking comment on the feasibility of allowing up to 24 MHz of spectrum between 413 and 457 MHz to be used on a secondary basis as part of the Medical Data Radiocommunication Service in Part 95 of the FCC rules.
The desirability of the Mann Foundation's objective is beyond dispute. Their researchers have developed a wireless medical micro-power network to tie together tiny devices implanted in victims of paralysis, creating an artificial nervous system to restore sensation, mobility, and function to paralyzed limbs and organs. The Mann Foundation argues that the frequency range just above 400 MHz is optimum for their application, which requires no more than 1 milliwatt of RF spread across about 5 MHz of bandwidth. However, recognizing the presence of a variety of incumbent radio services in that range, specifically including the amateur service, they have proposed four channels for flexibility in avoiding localized interference. Two of the four channels are 426-432 and 438-444 MHz; the other two are above and below the 420-450 MHz band.
The FCC's proposed rules raise two concerns. First and foremost, the devices would be required to accept interference only from stations authorized to operate on a primary basis. The Mann Foundation has assured us that amateur stations will not cause its system to malfunction, so we see no reason why this cannot be reflected in the rules even though our allocation is on a secondary basis. Second, while the Mann Foundation researchers appear to have done their homework, others who try to take advantage of the new rules may not be as rigorous.
The FCC is allowing 90 days for public comment after publication of the Notice of Proposed Rulemaking (NPRM) in the Federal Register. Of course, the ARRL will be filing comments; members are welcome to share their thoughts with us for possible inclusion in the League's submission. You also may file comments directly with the FCC as individuals or clubs -- but if you do, please read the NPRM first and respond to the questions that the Commission has posed. Form letters and expressions of opposition without anything to back them up will serve no useful purpose when weighed against the hopes and dreams of paralyzed veterans.
David Sumner, K1ZZ
ARRL Chief Executive Officer