Hooligan
Member
Occuring right now (7:10PM local Sunday) & starting at least 2.5 hours ago when I first noticed it, the SF Bay area is being blanketed with interference on the emergency frequency of 121.50MHz.
I was up in the Marin Headlands all day (without a radio on) but first noticed the signal a few minutes after crossing into SF from the Golden Gate Bridge on the Uniden BC-796 hooked up in my car. Signal was full-scale with audio characteristics also indicating it was very strong. At first, I thought it was an unusual case of EMI from a bus behind me, then maybe from within my car, but I picked it up on 4 different radios, and the signal did start to fluctuate as I headed S to my home in central San Mateo County.
I'm now picking up the signal in my living room, using a Yaesu VX-5 handheld & GRE-PSR-500.
The audio kind of sounds like FSK/RTTY and changes pitch a couple times each minute. I'm not hearing it on 243.0MHz, and it's definitely not an EPIRB, though the poor guys at USCG Sector San Francisco gave out a Notice to Mariners on 16 about "a 121.5MHz EPIRB being audible in the SF area..."
While many airports in the SF Bay area have a receiver for 121.5, most of them don't have transmit capability, so that if a plane were to declare an IFE on it, 20+ different airports wouldn't try to reply back. This 121.5 signal is definitely coming from an FAA Remote Communications Outlet or military Ground-Air Transmit/Receive site high above average terrain.
My educated guess based on signal strength during my drive home is the emitter is at the FAA/JSS site at the old Mill Valley Air Force Station atop Mt Tam, the separate FAA RCO around the 'mid-peak' area of Mt Tam, or an FAA/NORAD/Navy site near Half Moon Bay. The Monument Peak area of the East Bay Hills above Fremont has an RCO but I think a signal from there would have been weaker for me in SF. Likewise RCO at Black Mountain wouldn't have come in so strong for me in SF.
My associate 'Portable-John' in the Concord area hears it about half-scale, my associate 'BS' in Discovery Bay hears nothing using his VX-5.
An FAA Electronics Technician friend of mine wasn't familiar with the noises being transmitted on 121.5, and he called Oakland ARTCC to discuss it around 5PM.
I'm listening to Civil Air Patrol freqs & the FAA 'C3' LMR channels now for any related comms.
This sort of thing happened in Southern California earlier this year & that signal lasted for a couple days.
Tim
I was up in the Marin Headlands all day (without a radio on) but first noticed the signal a few minutes after crossing into SF from the Golden Gate Bridge on the Uniden BC-796 hooked up in my car. Signal was full-scale with audio characteristics also indicating it was very strong. At first, I thought it was an unusual case of EMI from a bus behind me, then maybe from within my car, but I picked it up on 4 different radios, and the signal did start to fluctuate as I headed S to my home in central San Mateo County.
I'm now picking up the signal in my living room, using a Yaesu VX-5 handheld & GRE-PSR-500.
The audio kind of sounds like FSK/RTTY and changes pitch a couple times each minute. I'm not hearing it on 243.0MHz, and it's definitely not an EPIRB, though the poor guys at USCG Sector San Francisco gave out a Notice to Mariners on 16 about "a 121.5MHz EPIRB being audible in the SF area..."
While many airports in the SF Bay area have a receiver for 121.5, most of them don't have transmit capability, so that if a plane were to declare an IFE on it, 20+ different airports wouldn't try to reply back. This 121.5 signal is definitely coming from an FAA Remote Communications Outlet or military Ground-Air Transmit/Receive site high above average terrain.
My educated guess based on signal strength during my drive home is the emitter is at the FAA/JSS site at the old Mill Valley Air Force Station atop Mt Tam, the separate FAA RCO around the 'mid-peak' area of Mt Tam, or an FAA/NORAD/Navy site near Half Moon Bay. The Monument Peak area of the East Bay Hills above Fremont has an RCO but I think a signal from there would have been weaker for me in SF. Likewise RCO at Black Mountain wouldn't have come in so strong for me in SF.
My associate 'Portable-John' in the Concord area hears it about half-scale, my associate 'BS' in Discovery Bay hears nothing using his VX-5.
An FAA Electronics Technician friend of mine wasn't familiar with the noises being transmitted on 121.5, and he called Oakland ARTCC to discuss it around 5PM.
I'm listening to Civil Air Patrol freqs & the FAA 'C3' LMR channels now for any related comms.
This sort of thing happened in Southern California earlier this year & that signal lasted for a couple days.
Tim