ARRL, DoD, FCC Try to Come to Terms with Pave Paws

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

The ARRL has sent out more than 100 letters to repeater owners/trustees who have repeaters affected by the "Pave Paws" radars (PPR). 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 ARRL is working with the US Department of Defense (DoD) to develop a plan to mitigate alleged interference from 70 cm ham radio repeaters to this military radar system on both coasts.

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 on the table.

The Amateur Radio Service is a secondary user in the 420-450 MHz band, both by the Table of Frequency Allocations and the FCC Part 97 regulations. As such, Amateur Radio licensees, jointly and individually, bear the responsibility of mitigating or eliminating any harmful interference to the primary user, which in this case is the Government Radiolocation Service that includes the DoD Pave Paws systems.

The letters sent to affected repeater owners/trustees give them an up-to-date briefing on the ongoing negotiations with the US Air Force, as well as outlines the DoD's plan. The DoD has indicated a willingness to try a mitigation proposal, but they have also indicated their need is for these issues to be resolved sooner rather than later. With that expediency in mind, the proposed mitigation strategy is as follows:

• All repeaters on the DoD list in the affected areas will immediately reduce power to 5 W transmitter power output (TPO). Each repeater licensee/trustee should contact Henderson to confirm this once this has been done for their system. Confirmation of this being done is needed from each repeater owner by Friday, June 15, 2007.

• The ARRL will provide the Longley-Rice calculations for each repeater to the DoD by June 15, 2007. The DoD will provide engineering data to the ARRL and FCC by June 15, 2007. These studies will be reviewed by the DoD, the ARRL Lab and the FCC to determine the amount of mitigation necessary for each repeater. Based on this review by the DoD, additional mitigation proposals for individual repeaters (including further power reductions, lowering of antenna heights, use of more directive antennas and other possible mitigation techniques) will be provided by the ARRL as needed to individual repeater owners. If there is a disagreement on the conclusions, a conference call will be held to resolve any outstanding issues.

• All interference must be resolved no later than August 1, 2007.

• Beginning in August 2007 (and continuing on a periodic basis), the DoD will have a follow-up engineers study at each PPR site to ensure corrective actions have been taken and to ensure that successful mitigation continues.

ARRL Working Closely on Plan to Mitigate Interference

According to the DoD, the in-band interference from Amateur Radio fixed FM voice repeaters has increased to an unacceptable level. Pave Paws radars are used for national security functions, including early detection of water-launched missiles. They are critical to our national defense and are in use 24 hours per day, seven days per week.

The goal of the ARRL has been to develop and implement a plan that would mitigate the interference, and at the same time to permit the repeaters to continue operation and to operate on as liberal a basis as possible. To do so, the League has offered to work closely with the two involved repeater coordinating groups, as well as the individual repeater owners, sharing information and dealing with this issue on a coordinated basis with all stakeholders.

The League has also been in contact with representatives of the FCC. They have the ultimate responsibility for enforcing any mitigation plan, up to and including ordering specific repeaters to shut down operations. The FCC is aware of the complex nature of this problem and the mitigation strategy being proposed by the DoD.

As secondary users on the band, the ARRL has few options, and all options involve cooperation with the DoD. It is hoped the Longley-Rice calculations from the ARRL and the DoD's engineering studies will provide enough data to allow as many of the repeaters in the affected areas as possible to remain on the air at reasonable power levels.

It is entirely probable that even with extreme mitigation techniques, some repeaters in close proximity to the PPR sites may have to be shut down permanently. If that happens, official notice would come from the FCC. It is also possible that some repeaters might be required to operate permanently at a lower power level in the areas near these Air Force bases. In those cases, the League will be in contact with the individual repeater owners with that information and the FCC will be notified.

Repeater Owners/Trustees Need to Comply

Henderson requests that all repeater owners/trustees affected by this issue immediately implement the 5 W TPO for your repeater/s; please contact his office by June 15 indicating if you have implemented the power reduction. This will allow the ARRL to have voluntary compliance on hand that can be used to show the cooperation of the amateur community.

Henderson stresses that it is to each repeater's long-term advantage to implement the power reduction as soon as possible. The DoD indicated they will be collecting engineering data during June. This presents the opportunity to assess a repeater's actual impact at the lower power level and a more honest determination of its continued potential for harmful interference to the PPR sites. If any repeaters are running at higher power levels, then the determinations can only be based on assumptions rather than on actual data.

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

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