[amsat-bb] FW: ARLB013 ARRL aiding effort to mitigate repeater interference to military radars

tjjapha@earthlink.net tjjapha at earthlink.net
Tue Apr 24 05:30:10 PDT 2007

Hi All,
Should this ARRL msg. cause us to worry about the future of mode B
Tony, N2UN

> [Original Message]
> From: ARRL Web site <memberlist at www.arrl.org>
> To: <tjjapha at earthlink.net>
> Cc: <Subscribed ARRL Members:>
> Date: 4/24/2007 12:06:01 AM
> Subject: ARLB013 ARRL aiding effort to mitigate repeater interference to
military radars
> ARLB013 ARRL aiding effort to mitigate repeater interference to 
> military radars
> QST de W1AW  
> ARRL Bulletin 13  ARLB013
> From ARRL Headquarters  
> Newington CT  April 23, 2007
> To all radio amateurs 
> 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 at arrl.org, or 860-594-0236, with
> specific questions or issues associated with this situation.
> /EX

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