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By Richard J. Cabral, W1RJC
Communications
as we know it on the 70 centimeter (440 MHz) amateur
band are slowly changing in our region. For decades,
the FCC has allocated the United States Air Force (USAF)
as primary and amateur radio as secondary on this 420–450
MHz band. What this means is government related usage
takes precedence over amateur use. In certain areas
of the country, amateurs are restricted to no more than
50 watts output power in order to prevent interference
to these primary users.
Locally, the 50 watt output power restriction is
in place due to the Otis Air National Guard Base located
within the Massachusetts Military Reservation on Cape
Cod. They operate a missile warning and space surveillance
system called PAVE PAWS. PAVE is an Air Force program
name, while PAWS stands for Phased Array Warning System.
PAVE PAWS basically sends pulses across the entire band
at thousands of watts through a special phased array
antenna.
If you have ever operated on the 440 band locally
and heard a lot of “snap, crackle and pops”
on weaker signals (most notably on users operating through
repeaters), chances are you were hearing the effects
of PAVE PAWS transmissions. The PAVE PAWS system at
Otis AFB is one of only three in operation in the U.S.,
with the other two being Beale AFB, California, and
Clear Air Force Station, Alaska. In each of the three
locations, a 50 watt restriction on 440 is in place
within a set mile radius of the AFB.
PAVE PAWS Radar Screen
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Nuclear Warning System Map
Up until the last few years, amateurs have successfully
shared the 440 band with the USAF without much problem
in New England. This began to change about 4 years ago
however, when the USAF requested a ban on amateur use
for a section of the 440 band. The New England Spectrum
Management Council (NESMC) was notified that hams in
Maine, Massachusetts, New Hampshire and Rhode Island
must discontinue using 439.150 – 441.250 MHz.
A few links and repeaters were forced to change frequency
and re-coordinate. This restriction was put in place
by the request of the Millstone Hill Digisonde (radar
system), which is owned and operated by the US Air Force
Research Laboratory (AFRL) at Hanscom Air Force Base
in Bedford, MA.
The next round of changes followed in the summer
of 2006 and remains on going. NESMC was notified of
over a dozen 440 repeaters within an 80 mile radius
of Otis AFB that is causing interference to their PAVE
PAWS system. As of March 2007, the USAF has sent proof
of the interference to the FCC, and it is expected that
a decision will be made soon on what action will need
to be taken.
Realistically, there are three possible decisions
that the FCC may reach. In our favor, the FCC may allow
the repeaters in the affected areas to remain on the
air. Secondarily, they may allow the repeaters to remain
on the air, but be required to change frequency. Worst
case scenario is that the FCC can order all the repeaters
affected to cease and desist completely, forcing them
to shut down and not operate anywhere on the 440 band.
All of these restrictions draw one question to the
amateur community in New England. Why are amateur transmissions
on 440 suddenly causing harmful interference to USAF
stations that have peacefully co-existed with us for
decades? In a search of the FCC web site, there appears
to be no current information on this on going issue.
Likewise, calls I made to Otis AFB has remained unanswered.
We will just have to wait and see what the FCC’s
decision will be. Despite the hardship to amateurs,
the fact remains that we are secondary operators on
440 and the FCC has every right to grant precedence
to the USAF.
Related links of interest:
Pave Paws: http://en.wikipedia.org/wiki/PAVE_PAWS
NESMC: http://www.nesmc.org
FCC: http://www.fcc.gov
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