I can see if I can get anything from the San Bernardino area
Hearing a mystery trunked system on federal UHF spectrum
- Thread starter kj6psg
- Start date
kj6psg
Member
It's different based on the talkgroup and radio. Monitoring is generally unattended so I'm not paying close attention to what smudges on the waterfall correspond to what systems and radios.
- $BA5 radio 4 has a very slow fade and is often quite strong (much more so than anything else). It is generally heard simultaneously on both receivers. I do not hear anyone else on $BA5 on both receivers, and they are obviously talking to someone because the VC assignment does not drop.
- $A9D talkgroup 28 has a user with some fade talking to a unit (I presume stationary) that is stronger and without fade. They are generally not heard in San Diego but there are exceptions.
mmckenna
I ♥ Ø
OK, thanks.
A couple of random trains of thought on this:
You may have been hearing a distant uplink from a BDA system. If the trunked site was outside of your coverage and the BDA system wasn't, it ~might~ explain hearing the subscriber side only.
That would probably present as fairly consistent signal levels around the same timeframe.
Other idea that ~might~ explain both you and San Diego hearing it would be one of the Navy installations on one of the Channel Islands, but not hearing the control channel doesn't jive with that very well. Feds/NTIA do some odd stuff sometimes, but a control channel would be within the lower UHF band.
Consistent UHF tropospheric ducting lasting this long would be something rare, but I'd expect to hear the control channel more reliably with higher transmitter power and a better antenna.
Shipboard might make some sense, but anything that could be heard from both Ventura and San Diego would be well off the coast and would likely be moving, not sitting still. But, again, wouldn't explain the lack of control channel.
Mobile extender/repeater might explain some of this, but I have no idea if any of the feds are doing that on this band. But it being stationary this long would be odd.
A conventional repeat of a trunked system somewhere else might explain it, I've heard some federal repeater linking in this section of the UHF band.
A beam antenna might help narrow things down to a general area. Or not, if it's reflecting off the mountains.
Quite the challenge to figure out, looking forward to seeing what you find.
A couple of random trains of thought on this:
You may have been hearing a distant uplink from a BDA system. If the trunked site was outside of your coverage and the BDA system wasn't, it ~might~ explain hearing the subscriber side only.
That would probably present as fairly consistent signal levels around the same timeframe.
Other idea that ~might~ explain both you and San Diego hearing it would be one of the Navy installations on one of the Channel Islands, but not hearing the control channel doesn't jive with that very well. Feds/NTIA do some odd stuff sometimes, but a control channel would be within the lower UHF band.
Consistent UHF tropospheric ducting lasting this long would be something rare, but I'd expect to hear the control channel more reliably with higher transmitter power and a better antenna.
Shipboard might make some sense, but anything that could be heard from both Ventura and San Diego would be well off the coast and would likely be moving, not sitting still. But, again, wouldn't explain the lack of control channel.
Mobile extender/repeater might explain some of this, but I have no idea if any of the feds are doing that on this band. But it being stationary this long would be odd.
A conventional repeat of a trunked system somewhere else might explain it, I've heard some federal repeater linking in this section of the UHF band.
A beam antenna might help narrow things down to a general area. Or not, if it's reflecting off the mountains.
Quite the challenge to figure out, looking forward to seeing what you find.
How about trying to get a line of bearing -- RDF the emissions, or just put the freqs/system in a mobile radio & travel up/down the coastline? I'm assuming you've ruled-out nearby ashore stuff Naval Base Venture County's Pt Mugu/Port Hueneme & the ANG & USCG stations, Vandenberg SFB & the BOP FCIs at Lompoc, so I agree it's maybe a HYDRA system, but don't forget there's DOD Activity out on some of the Channel Islands.
