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Report on CORF Meeting, 16-17 October 2006 Report on the CORF Meeting, 16-17 October 2006

Patrick C. Crane
20 October 2006

The fall meeting of the Committee on Radio Frequencies of the National Academies was
held at the Array Operations Center of the NRAO in Socorro, NM on 16-17 October
2006. The familiar names among the attendees were David DeBoer, Steve Ellingson, Jim
Moran, Paul Vanden Bout, Mike Davis, Tom Gergely, and Andy Clegg; other attendees
represented the remote-sensing community and NRC staff. Greg Taylor and I were
allotted 45 minutes on Monday afternoon to discuss the Long Wavelength Array and our
concerns about frequency coordination issues. Greg gave a status report on the LWA and
some of the science. I discussed frequency coordination.

The two main issues that I raised were broadband over power line (BPL) and the
reallocation of television channels for digital television. FCC regulations currently
provide for an exclusion zone with a radius of 65 km around the VLA in the band 73.0-
74.6 MHz and consultation zones around other radio observatories listed in footnote
US311. Obviously, we prefer similar exclusion zones around individual LWA stations
(or the whole array) in all the relevant radio-astronomical allocations. Not surprisingly,
the FCC is unlikely to provide such protection at this early stage of the project. Tom
Gergely and Andy Clegg of the NSF will consider how to proceed; the initial steps are
likely to be the registration of individual stations in the FCC database and in the
Government Master File.

The transition to digital television (DTV) is now scheduled by act of Congress to occur
on 18 February 2009. The channels to be auctioned or assigned to public-safety service
are 52-69. Full-power digital television stations will be restricted to the core channels
2-51 (low-power, repeater, and translator stations are not required to switch to digital
transmission.) However, the FCC appears to be encouraging DTV stations to move out
of channels 2-6, with what goal I have no idea.. The final results should be known soon
because the FCC is scheduled to release the final DTV Table of Allocations soon, but
currently there appear to be no DTV channels 2-6 in New Mexico and adjacent states or
in Mexico within 275 km of the border. This, of course, makes the short observation of
DTV channel 4 on 22 July at the LWDA site inexplicable which leaves anomalous
propagation from who knows where.

Another FCC initiative that Andy Clegg described is to fill in TV white space which
means, for example, that in Albuquerque channels 3 and 6 are vacant and the FCC wants
to allow other services to use those channels locally. There are impediments like the fact
that video equipment like VCRs use channels 3 and 4 for their output signals and other
limitations to be identified. Of course, radio astronomy likes to use those empty
channels, too.
Another scientific user that uses empty VHF channels is the Lightning Mapping Arrays
that are being installed around the country by lightning researchers at New Mexico Tech
(see
www.lightning.nmt.edu/nmt_lms/)
. These systems were described by Paul Krehbiel of
New Mexico Tech. They detect the impulsive emission from lightning strokes in an
unused television channel with time-of-arrival detectors at perhaps 8-10 stations
distributed over an area ~60 km in size. They determine the three-dimensional
distribution of lightning and are another diagnostic of the severity of thunderstorms. In
fact, an LMA was just installed in the Washington area for research with the Weather
Service. I will try to organize a lunch talk the next time some one in the group visits
Washington, probably in the spring.

If one googles on lightning mapping array one will find many other installations
around the country. In fact, they are interested in studying thunderstorms in West Texas
which grow and move on to East Texas. So I told Paul the Applied Research Laboratory
at the University of Texas has a site at Wink and gave him Tom Gaussirans name.

On Tuesday afternoon the Committee members came to the VLA site for a tour of the
EVLA and the Alma Test Facility. And they also visited the LWDA site while I was
moving stuff out of the trailer and were very interested in what we were doing.