ARRL

ARRL General Bulletin ARLB013 (2007)

SB QST @ ARL $ARLB013
ARLB013 ARRL aiding effort to mitigate repeater interference to 
military radars

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ARRL Bulletin 13  ARLB013
From ARRL Headquarters  
Newington CT  April 23, 2007
To all radio amateurs 

SB QST ARL ARLB013
ARLB013 ARRL aiding effort to mitigate repeater interference to 
military radars

The ARRL has been working with the US Department of Defense to
develop a plan to mitigate alleged interference from 70 cm ham radio
repeaters to military radar systems on both coasts. Citing an
increasing number of interference complaints, the US Air Force has
asked the FCC to order dozens of repeater systems to either mitigate
interference to the ''PAVE PAWS'' radars in Massachusetts and
California or shut down. Amateur Radio is secondary to government
users from 420 to 450 MHz and must not interfere with primary users.
The Commission has not yet responded. ARRL Regulatory Information
Specialist Dan Henderson, N1ND, stresses that the Defense Department
acknowledges Amateur Radio's value in disasters and emergencies and
is being extremely cooperative, and a wholesale shutdown of US 70 cm
Amateur Radio activity is not in the offing.

''The ARRL Lab is working up calculations on each repeater system the
Air Force has identified to determine where interference-mitigation
techniques offer a reasonable chance of keeping the repeater on the
air,'' Henderson says.

The situation affects 15 repeaters in the vicinity of Otis Air Force
Base on Cape Cod, Massachusetts, and more than 100 repeaters within
some 140 miles of Beale Air Force Base near Sacramento, California.

A US Air Force contractor identified the problematic repeater
systems last summer, but the situation didn't become critical until
the Air Force contacted the FCC a month ago. ARRL officials met with
Defense Department representatives in late March to discuss alleged
interference to the PAVE PAWS radar sites. Henderson has contacted
Amateur Radio frequency coordinators in both affected areas.

PAVE PAWS is a missile and satellite detection and tracking system,
and its facilities occupy essentially the entire 70 cm band -- one
factor that makes mitigation difficult. As a ''first step,'' however,
the ARRL is recommending that all affected repeater owners reduce
power -- possibly to as little as 5 W effective radiated power
(ERP).

''We understand the difficulty this may cause to owners and users,''
Henderson said, ''but the alternative to operating with a smaller
coverage area may be not operating at all.''

Henderson says the League is still seeking further information on
the problem. ''Until the Defense Department accepts a mitigation
plan, repeater owners should exercise patience,'' he cautioned.

Contact Dan Henderson, N1ND, n1nd@arrl.org, or 860-594-0236, with
specific questions or issues associated with this situation.
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