CDF uses approximately 30 VHF-hi frequencies for statewide use, with a few low band frequencies for administrative use. The VHF radio plan for CDF at first seems extensive but a quick explanation will show how simple it is and the organization of the frequencies.
Organization
Each VHF-hi frequency can be used in 3 different ways throughout the state. In one part, it may be used as a dispatch frequency, in another part it could be a tactical frequency for incident traffic, and in another part of the state it could be a wide-area command frequency for large incident admin traffic. For instance, 151.250Mhz is CDF dispatch for the San Benito/Monterey Unit, San Bernardino Unit, and the Lassen/Modoc Unit. It is also CDF Tact Channel 5, which is utilized in Butte, Lake/Napa and Nevada/Yuba/Placer Units. Even with all that, it is also utilized as CDF Command Channel 6, which covers the few counties north of San Francisco Bay. CDF Tacticals 14-23 are also the input frequencies for the repeater systems. This allows further tactical options. As a scanner listener, it takes a little coordination to figure out all of these uses. CDF is not meant to be monitored from a high elevation or elaborate antenna system. Because of the way CDF recycles their frequencies throughout the state, once you gain any elevation, you will start hearing the repeaters and Local nets from far away over what was the simplex tactical channels in your area. This can be annoying if you want to try and listen to a local tactical incident.
CDF Emergency Command Centers (ECC) are the brains behind CDF Radio. The dispatchers maintain radio control of all the various incidents in their respective units. Other agencies that work well with CDF often are dispatched out of the ECC. County and City fire departments, as well as ambulances can be dispatched on the same frequency as CDF resources. This may make things pretty busy on the Local Net, but the agencies all benefit by sharing the same info, most of the time they're all responding to the same incident anyway. The ECC is also the Unit's frequency coordinator. They will issue out tactical frequencies to an incident that needs them. They will also find aerial tactical frequencies (Victor nets) to use from the FAA etc. if the normal ones are all used up.
Each ECC dispatch has a name on the radio, the city that the ECC resides in. This is how you can tell which Local Net you're listening to. St. Helena, is the city where the ECC and Headquarters for Unit 14, Lake/Napa Unit resides in. All fire resources will call "St Helena" over the air to contact that ECC.
Local Net
CDF Dispatch's repeater system is called "Local Net", a term that goes back to the early 60's and 70's of CDF's Radio System. Anywhere in the state, Local Net means the frequency that the Unit's ECC uses for day to day radio traffic, including dispatching. Each Unit has a series of repeaters each covering certain geographical areas of the Unit. Each repeater is activated by a different CTCSS (also known as PL) tone. A fire engine that wants to talk on Local Net chooses the repeater with the best coverage. They switch repeaters by switching "tones." Tones 1 through Tone 16 are CTCSS tones standardized throughout the fire departments in the Nation by FIRESCOPE. The output of the Local Net is one tone, and can be determined by the second digit of the Unit's number. Unit 25 would program Tone 5 (which is 146.2) to only hear Local Net traffic and not nearby Tactical or Command traffic on the same frequency.
Tactical Net
Once units are on scene of an incident, they move all incident tactical traffic to a CDF Tactical Channel. CDF Tact 1 through 12 are used throughout the state (13 through 23 are utilized as input channels to CDF repeaters and used only for emergency overflow use.) The tactical traffic is simplex, usually engine and hand held radios. The Incident Commander usually stays on the mobile radio, with an excellent antenna to ensure everybody on the incident hears them. With the best antennas on your scanner, you will still only hear your own Unit's tactical traffic and maybe nearby traffic. Because of interference from the constant re-use of the CDF VHF frequencies, the CDF has been considering making it standard to use CTCSS tones on their tactical traffic, a practice that has been controversial with safety issues. The tone would be based on the Unit number's second digit like the Local Nets. If an incident were taking place in Unit 14, the tactical frequencies would have Tone 4 (136.5) to help minimize interference from nearby Unit's Local Nets or state Command Nets. I don't think this has been utilized yet due to interoperabilty problems.
Command Net
The Command Net is the frequency which command, logistics and administrative traffic takes place. Sometimes on small incidents the local net is used as the command net. If the incident grows, they can move to a seperate command repeater. Command Net repeaters are high level, wide coverage, repeaters scattered throughout the state. Command 1 and 2 are on unique frequencies not shared by anything else in the state. Originally this served the state just fine for command traffic. Recently however the state has had multiple large incidents in the same area, all requiring seperate command frequencies. The Incident Command would complain they could hear the other Incident Commands over the radio, which caused problems and safety concerns. The state decided to go cycle through their VHF freqs again and assign an existing tactical frequency the area Units were using to create a high-level powerful command repeater with that frequency. If the Command channel were being used, the frequency would be unusable for the low-powered tactical traffic, a sacrifice the Incident Commanders took to gain an additional Command channel.
Chief's Net
This system is a new system that hasn't really been implemented statewide yet. It wouldn't hurt to keep the respective freq in your scanner for general scan and see what pops up. You might hear DGS Telcom units testing on it, or some blips of info. Stay tuned. This project is slowed down by the state budget.