开云体育

Sydney Bradfield W4LUU, FAA Radio Frequency Manager, will appear as a guest speaker/ham on the PAPA System Thursday Night D-STAR Round Table at 8:00 pm DST (0300Z) on Reflector 12C, this Thursday September 27.

Sydney W4LUU is the chief engineer in FAA's Spectrum Management Division. He will speak about 23cm amateur radio interference with FAA air route surveillance radar, other RFI issues, how they track down interference sources, his agency's relationships with the FCC and ARRL, and will take questions.

Sydney provides a unique insight into the conflict between amateur radio's secondary use of the 23cm band and interference problems that have resulted in 23cm repeaters being turned off or changing frequencies.

If you operate digital in the 23cm band, this net is a must. Know the future of the 23cm spectrum as FAA and FCC agencies clamp down on certain ham operations as surveillance radar use modernises and expands.

Mike
N6HKH

Here are notes that I took from the Papa System round table with guest Sidney Bradfield, W4LUU, FAA Radio Frequency Manager.

FAA 23cm band long range (250 miles) radar is being upgraded to solid-state equipment with lower transmit power and more sensitive (20 to 40 db more) receivers, replacing existing tube-type high maintenance cost radars. 23cm ham transmitters can swamp the input of these new radar receivers. The radar receiver pass band is 10MHz wide. These problems were a surprise to the FAA because the old radars were compatible with existing ham repeaters. The higher receiver sensitivity is the big problem because they are hearing things now that they never heard before. Their pre-installation engineering spectrum studies do not consider secondary usage. They instead assume that a secondary user's frequency can be changed. FAA radars can be located anywhere from 1215-1400 MHz. They are usually located far from populated areas, but exceptions exist, such as in Southern California.

They use direction finding to locate interfering sources, which can also turn out to be unlicensed devices such as wireless cameras, personal computers, etc. ARRL, through frequency coordinators, is facilitating relocating repeater frequencies that interfere with these new radar installations. Hams have generally been cooperative and many problems have been successfully resolved. Sidney focused on west coast problems because that is where the first radar installations were made. ARRL now has the schedule and other info about rolling out these installations in other parts of the country. Release of this information is constrained for security reasons, and the ARRL was given the information but can only provide it on a "need to know" basis.

73, Roland W9HPX