I’m trying to figure out what CHP units do when there is a “keep radio traffic clear for emergency”. I would think there would be another channel for units that are not involved with the emergency traffic. I’m looking for the Valley Division channels. I have scanned all the Tac channels but nothing heard. Is there a tac channel for Valley Division?
CHP Channel 2?
- Thread starter Legal1313
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They'll either wait for the emergency traffic to clear (usually the case), they may switch to the Blue channel to hail a free dispatcher if they need something, or they may just telephone directly in to the dispatch center.
You mentioned Channel 2, I believe they can still talk car-to-car without being repeated on the base frequency by pushing the second button on their mic. If you live close to a freeway with a good antenna, you can monitor the mobile side (CH 2) and can catch mobiles talking to each other or direct to dispatch vs. being repeated over the base side (done in many metro areas). I was traveling through SLO county last week and heard mobiles talking to each other on Ch 2 (mobile freq) about looking for a particular vehicle.
In my 40 years of monitoring the CHP I've never heard any car to car traffic on the mobile frequency. It has always been simplex on the base frequency. This in the eastern Sierra, southern California, the desert from Baker to Blythe and the Bay Area. I don't travel as much as I used to in California so I guess they have changed procedures. I would imagine that when they talk on the mobile in the car to car mode, they have a different CTCSS tone so that the remote bases won't hear it. The remote bases I've been familiar with can receive both the mobile and base frequencies on the tone assigned to the dispatch center. I don't know if they always listen to the car to car traffic on the base frequency as they do have to transmit over it when communicating with other units. I'm in a rural area so they don't rebroadcast the mobile frequency on any remote bases the dispatch center has available. Some of the units working long construction projects will use the division blue base frequency when more than one unit is assigned to them.
Channel 1 is unit to dispatch and 1 repeater (in my area). Channel 2 is car to car simplex but dispatch has the ability to listen to this channel in the comm center as well. Blue is usually used when their main channel is either down or they have a special event or wide load escort going on.
This is an excellent website on CHP radio history:
The older mobile hand mics had two PTT buttons, “Station” and “Car-to-Car”. The station button transmits on the mobile frequency and receives on the base frequency. The car-to-car button transmits and receives in simplex on the base frequency.
Like es said, as far as I know there was never a simplex on the mobile frequency option.
CHP also doesn’t use repeaters in a traditional sense. Rather they use a console patch (which can be turned off by the dispatcher) that can re-routes the audio heard by the dispatcher on the mobile frequency and re-transmits it out the base frequency. They have receiver voting on the mobile frequency so the dispatcher replies on the closest remote base automatically, but the repeated mobile traffic on the base frequency (if the console patch is in use) can usually only be set up on one remote base transmitter. This is why you may hear the dispatcher clear but the mobiles very scratchy on the base frequency.
The older mobile hand mics had two PTT buttons, “Station” and “Car-to-Car”. The station button transmits on the mobile frequency and receives on the base frequency. The car-to-car button transmits and receives in simplex on the base frequency.
Like es said, as far as I know there was never a simplex on the mobile frequency option.
CHP also doesn’t use repeaters in a traditional sense. Rather they use a console patch (which can be turned off by the dispatcher) that can re-routes the audio heard by the dispatcher on the mobile frequency and re-transmits it out the base frequency. They have receiver voting on the mobile frequency so the dispatcher replies on the closest remote base automatically, but the repeated mobile traffic on the base frequency (if the console patch is in use) can usually only be set up on one remote base transmitter. This is why you may hear the dispatcher clear but the mobiles very scratchy on the base frequency.
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How does simulcast in the LA area fit into that? It's been too long for me to remember, but I thought simul was the default.
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