Late last month we reported on a Notice of Proposed Rulemaking contemplating use of the 78-81 GHz band to detect “foreign object debris” at airports. If you feel moved to comment on that proposal, your deadlines have now been set: comments are due by February 10, 2012, and replies are due by February 27.
Devices will be used to detect runway debris; other applications are possible.
The FCC seeks comment on radar operations in the 78-81 GHz band, and in the meantime, has granted a waiver for limited use.
There has been a lot of regulatory interest lately in radar devices above 75 GHz, up in the “nosebleed” portion of the spectrum. Back in 2009, the FCC considered, and later granted, a waiver to allow the Atlanta airport to use 77-76 GHz radars to track aircraft and vehicles on the ground. The beginning of 2010 saw a proposal to use 78-81 GHz to measure the levels of substances inside large industrial tanks; there, too, the FCC granted a waiver, while a rule change is still pending. Last May, the FCC proposed to relax the rules for vehicle radars at 76-77 GHz, which provide for automatic braking when the car senses an obstacle ahead. That rule, too, is still under consideration.
Now the FCC has revisited the airport environment, with a proposal to authorize 78-81 GHz radars to detect “foreign object debris,” or FOD – apparently a term of art in the airport business. We are all in favor of FOD detection, remembering that a stray piece of metal on the runway, dropped from an earlier plane, tripped up an Air France Concorde in 2000 at the cost of 113 lives. Apparently aircraft shed parts more often than most of us realize. Other common forms of FOD include misplaced tools, equipment and supplies, rocks and pavement fragments, luggage, and wildlife.
A close reading suggests the FCC is determined to approve FOD radars. But it is not sure how: whether to authorize 78-81 GHz radar on an unlicensed basis, like cordless phones, or under license, like taxi radios. Another question is whether to restrict the band to use at airports, or to permit other applications as well. A third question is whether radar users should have to coordinate their operations with others who share the band.
All of these questions turn in large part on the need to protect radio astronomy from interference. Radio astronomers have a primary allocation across most of the band, which they use to identify molecules in remote stretches of space. The good news is that radar signals at these frequencies tend to form narrow beams and do not propagate well, thus cutting the risk of interference. On the other hand, though, radio astronomy facilities use exceedingly sensitive receivers, and so can be disrupted by even a very low level of interfering signal.
While the rulemaking proceeds, the FCC has granted one company a waiver to market equipment in the band, solely for FOD detection at airports, and only under a license.
Comments and reply comments are on a relatively short fuse: 30 and 45 days, respectively, after publication in the Federal Register. We will post the actual due dates when they become available.
Not as momentous as the Julian-Gregorian shift, but changes you might want to note nonetheless
Back in January we reported on a proposal to allow unlicensed operation in the 77-81 GHz band for “tank radar” use. The Commission’s Notice of Proposed Rule Making has now been published in the Federal Register, which in turn has established the deadlines for comments and reply comments. Comments are due by June 2, 2010 reply comments by July 2, 2010.
And in February, we called readers’ attention to the First Report and Order and Notice of Proposed Rule Making (FRO/NPRM) in the rural radio proceeding. There the Commission adopted a Section 307(b)-based “tribal priority” for new AM and FM allotments, and separately invited comments on possible further tweaks to that priority (e.g., whether and how to apply that priority to Native American Tribes who do not possess tribal lands). The FRO/NPRM has also been published in the Federal Register. That publication sets the comment deadlines for the NPRM section of item (comments are due by May 3, 2010, reply comments by June 2, 2010). Additionally, the publication makes the “tribal priority” and other changes adopted in the R&O portion effective as of April 5, 2010. (Check out our earlier post on this for a summary of the various changes.)
While the “tribal priority” is not likely to affect the lay of the AM and noncommercial FM land for the time being – since new allotment proposals there require the opening of a “filing window” by the Commission, and no such windows are currently on the horizon, as far as we can see – it could affect commercial FM drop-in proposals early on. However, in view of the lag time between (a) the inclusion of new commercial channels in the Table of Allotments and (b) the opening of a window opportunity to file for those channels, increased service to Native American tribal lands as a result of the “tribal priority” is still probably a ways away.
FCC moves to allow 77-81 GHz radars inside storage tanks.
Driving through an industrial area, looking at the huge storage tanks that dot the landscape, don’t you wonder how the users of the tanks know how much stuff is inside? Neither did we, until recently. If we thought about it at all, we imagined some kind of giant float, like the thing in the back of the toilet, except much bigger. But that couldn’t be very reliable, considering it’s not all that reliable in the toilet, either.
Many of the big tanks have a better system. A radar device sits up on the ceiling, looking down. It transmits short pulses, measures the time they take to come back, and computes the distance to the surface inside. Using radar avoids problems of corrosion, contamination, and the endless repairs needed for moving parts in the vicinity of liquids.
Other equipment inside the tank – valves, agitators, filling pipes, and so on – also reflects radar signals, as do the tank walls themselves, and that can lead to errors. One solution is a radar beam narrow enough to miss the other structures and strike only the liquid directly below. But then those pesky laws of physics intervene. The most feasible way to produce a narrow beam, using a reasonably sized antenna, requires transmitting at high frequencies.
The manufacturers of tank radars favor the 77-81 GHz band. This is well up in the nosebleed portion of the spectrum, among the very highest frequencies the FCC has ever authorized. From an engineering standpoint, it is an excellent band for the purpose. Not only do signals at these frequencies form tight beams, but they are absorbed by metal and concrete tank walls, and so do not escape the tank to threaten interference to receivers outside.
From a legal standpoint, though, the band has a problem. Everyone agrees that tank radars should be authorized on an unlicensed basis, like Wi-Fi and cordless phones. But 77-81 GHz falls within a list of “restricted frequencies” that are closed to unlicensed transmitters. Most frequencies on the list accommodate highly sensitive services such as GPS, search-and-rescue, and satellite downlinks. But when the FCC drew up the list in the 1980s, it deemed everything above 38.6 GHz to be restricted. There was little activity up there in those days, and the FCC reasoned it could always de-list frequencies later, if the need were to arise. And in fact the Commission has since done so for several individual bands, for certain purposes. But otherwise the blanket prohibition on unlicensed operation above 38.6 GHz remains in force.
As a result, despite a near-unanimous view that unlicensed 77-81 GHz tank radars will not cause interference, the FCC is legally barred from allowing them under the present rules. The FCC has accordingly launched a proceeding to change its rules to permit these radars to operate. It also issued a temporary waiver allowing use of these radars, under certain conditions, while the rulemaking is pending.
The only opposition so far comes from a group of radio astronomers, who have primary rights at 77-81 GHz. Fearing interference to their telescopes, they asked for a mandatory separation of two kilometers between tank radar installations and the astronomers’ sites. The FCC indicated its intention to deny the request, on the ground that any slight leakage from inside the tanks would be too weak to cause interference.
The rule change is obviously the right thing to do. But it points up a broader problem: the need to abolish the blanket prohibition on unlicensed operation above 38.6 GHz. Rather than continue to exempt various bands piecemeal, the FCC should decide once and for all which bands really do need protection and drop the rest from the restricted list. Why does this matter? The initial request on 77-81 GHz tank radars reached the FCC in November, 2006. (Two more followed in April and July, 2007.) Three years is a long time to wait for proposed rules and a temporary waiver, especially for a technology widely considered to be non-interfering.
More is at stake here than just tank radars, important as those are. As the lower part of the spectrum fills up, and as prices drop for equipment that uses the upper reaches, demands on the over-38.6 GHz segment will rise. Amending the list of restricted frequencies now will help to avoid unnecessarily long delays in the future.
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