Does anyone know the frequencies for NMSP-Las Cruses area? The receive and transmit frequencies? And PL Tone. I can hear the SP Dispatcher, but can't hear the Officer.
I'm not sure it has been made clear here, but the NMSP does not use repeaters, they use remote base stations. A repeater re-transmits the mobile or input frequency. A remote base is a just like the base station in an office, except a base station radio has been placed in a building on top of a mountain somewhere. In flatter areas of the country, such as the midwest the remote bases are located at the base of towers that have antenna hundreds, or even thousands of feet, above these bases. The remote base is connected with an office or dispatch center using radio link frequencies, UHF in a lot of cases, phone lines or microwave. The State of New Mexico uses remote bases for the State Police, New Mexico Division of Forestry and New Mexico Game and Fish. In the case of State Forestry the mobile calls in the the same frequency the base station does. This is simplex, just like car to car. In the case of Game and Fish the remote base stations transmit on 44.80 MHz and the mobile units receive on this frequency also. However, the mobiles transmit to the base stations on 44.920. In most locations, when not on a high peak, you will just hear the base station, not entirely because the base station might be more powerful, but because it is located above the average terrain.
So it is with the New Mexico State Police, 155.520 is transmitted by the base station and the cars transmit 155.535 to the base station. You hear the base station, located on a high peak, but not the mobile, because it is down in a canyon, on the other side of a ridge or past the horizon to you. The high mountain top can "see" all of this due to its height.
If you drive or walk to a tall peak, it doesn't need to be one with a radio installation on it, you will hear a lot more than you do in town. You might hear both sides of the conversation, between a NMSP officer and the dispatch center. You also might not, even if you are right next to the remote base the dispatcher and officer are using to speak to each other. Why? The remote base receiver is employing an antenna that is far more sensitive to weak signals than the antenna on your handheld or mounted on your car. It is also up on a mast or tower that, while not being as tall as the antenna towers in the midwest, is taller than your car or handheld.
In town or back out on the flats you will only hear the car or mobile side of the conversation when the car is close enough to your receiver to pick it up directly, which can be just a few miles depending on the terrain around you. I hope this helps as the word "repeater" was used in the posts above and you should understand that a repeater is not being used.
In some areas of the state, NMSP uses repeaters for some reason. When I lived in Magdalena, New Mexico I could not hear the cars along I-25 talking with Socorro on 155.535, a distance of about 25-30 miles, but heard the remote base on "M" mountain just west of town. In the area around Santa Fe the State Police use a repeater, so I could hear both sides of the conversation in that case. The repeater's location was on a mountain top that was over 100 miles away, but did not have a mountain ridge of the size that blocked the signal from booming in at the Ranger Station housing compound above town on State Highway 107.
You might be curious why a separate frequency is used for the mobile side instead of a single frequency. The mobile units can use the base frequency to talk car to car without switching to a channel that has a completely different frequency. The advantage here is that should dispatch call them while they are listening to the other car, the more powerful base station will be heard and they don't miss anything. If they are on another frequency they won't hear the dispatcher while they are talking car to car.
The person in the mobile never has to be concerned about what "repeater" should be used in different areas of, in this case, their district. The remote bases are all connected into an audio filter that only lets the sound pass through from the remote base that has the best signal. This "filter" is called a "voter." The voter compares the audio from all the different remote bases the mobile might be received by and chooses the best. The officer in the car just keeps the radio on the same channel, no matter what part of the district he/she is located in. At the dispatcher's console there will be lights showing each remote base location and when a car starts transmitting many of the lights might start blinking, but the voter picks the remote base with the best signal and the light for it shows up solid. This allows the dispatcher to in turn use the remote base that shows the solid light. The officer might continue talking and pass out of one remote base's reception area and into another. That new remote base's light then will stop blinking and the dispatcher will then use it to talk back to the officer. Now with computer consoles the display might not look exactly as I've described it, but the console at the Magdalena Ranger Station looked like this when I worked there, sometime back in the Hoover administration (ha!), actually it was during the Carter and Reagan administrations, the last 3 tears of the former and the first year of the latter.
The Socorro District of the NMSP uses 4 remote bases along U.S. 60. One on the previously mentioned "M" Mountain, Davenport Lookout, located northwest of the town of Datil, another near Pie Town, and another near Red Hill, New Mexico near the Arizona state line. An officer responding from the Arizona state line to an accident just west of Socorro keeps the radio on the same channel the entire time. The remote base and voter system took care of the rest.
I hope this helps. I know it is a long explanation, but the posts seemed to indicate that this information would be helpful. Here in California the CHP uses remote bases and the same question about not hearing the cars comes up very frequently.
