I only look at fire channels but it has been publicly disclosed NTIA assignments have been changed over the last two years. All the systems I am aware of have been changed to low frequency is the mobile and control station side. All repeaters transmit on the high side of a pair. It seems to be a new NTIA rule.
If you're seeing frequency assignments that don't match this, double-check your code plug. Not hearing anything? NTIA has probably assigned a new frequency pair. This may apply to all federal VHF. I don't know. I see this looking at Interior, USFS, and NIFC assignments across federal VHF. This pattern seems to cover all of California. This will make it easier to put filters in front of receivers.
This is the opposite of how I was trained for FCC-assigned frequencies. I was trained the higher frequency is used for mobile and control stations. It's not a rule for FCC assignments, but interleaving a bunch of transmitters and receivers can make a mess.
This area can be used to talk about San Diego federal radio scanning. This includes Border Patrol, Homeland Security, DEA, FBI and other 3 letter agencies.
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