[Milsurplus] Fw: [Repeater-Builder] ARRL Aiding Effort to Mitigate Repeater Interference to Military Radars

[Dick]

FYI:

Dick W1NMZ
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ARRL Aiding Effort to Mitigate Repeater Interference to Military Radars

 A PAVE PAWS radar facility. [US Air Force Photo]

NEWINGTON, CT, Apr 17, 2007 -- 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. 
Amateur Radio is secondary to government users from 420 to 450 MHz and must 
not interfere with primary users. 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 or shut down. The Commission has not yet responded. The situation 
affects 15 repeaters within less than 100 miles 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. 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. "In order for the amateur community as a whole to succeed in this 
venture, it is going to require the cooperation of all affected repeater 
owners."

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, and this week Henderson contacted Amateur Radio frequency 
coordinating organizations in both affected areas -- the Northern Amateur 
Relay Council of California (NARCC) and the New England Spectrum Management 
Council (NESMC).
PAVE PAWS is a missile and satellite detection and tracking system, and its 
name is a half-acronym. "PAVE" is simply an Air Force program name. "PAWS" 
stands for "Phased Array Warning System." Although PAVE PAWS has been in 
existence since the late 1970s, the Cape Cod and Sacramento sites are the 
only remaining operational facilities in the US.

PAVE PAWS facilities occupy essentially the entire 70 cm band -- one factor 
that makes mitigation difficult. Feeding upward of 1800 active antenna 
elements, the broadband radar transmitters emit an average power output of 
more than 145 kW.

As a "first step" to mitigate the interference, 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." Amateur 
Radio stations already must abide by a maximum 50 W PEP power limitation in 
the areas around both Air Force facilities.

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. "Once the ARRL Lab has 
completed its propagation calculations, we will be in a better position to 
provide advice for specific repeaters on a case-by-case basis."

Contact Dan Henderson, N1ND (860-594-0236), with specific questions or 
issues associated with this situation.