Does CHP still use 72-76 Mhz VHF mid band?

[bubbablitz]

I live in Northwest Arizona and a few years ago, just out of curiosity, I plugged in all of the 72-76 Mhz frequencies into one of my scanner's banks just to see what I could find. Well, lo and behold, I was picking up the mobile end of CHP Barstow-Needles units coming off of Christmas Tree/Spirit Mountain Nevada. The quality varied due to the vast area between Needles and Barstow which I believe is 177 miles according to a highway sign leaving Needles, and there are other satellite receiver sites along the I-40. Now that I think about it, this was probably more than a few years, probably 20, since I would also pick up Caltrans mobiles, and they've long ago moved to 800 Mhz. Anyway recently, curious as a cat again, I've tried scanning that entire band for hours on end and have picked up nothing. Anyone in the know? Thank you.

 

[jeepsandradios]

Those used to be link frequencies from sites without microwave. I dont know if they are still in use but I would imagine not. I have not seen a 70mhz link radio at any site in 20+ years.

 

[AM909]

Looks like they are still renewing the licenses, though I looked at a few of them and they all had low-band or and/or UHF freqs on them as well, so it's possible that they are just not bothering to mod the mid-band stuff out when they retire them (how inconsiderate! ). I can't imagine it would still be necessary or worthwhile to maintain the equipment.

 

[techman210]

Most, if not all of them have disappeared. One reason is radios in the "midband" VHF band are unobtainium, and the other is they cannot carry two 4-wire voice paths (one for their dispatch channel and the "Blue" channel) required at each site. So they would have to have two of these radios.

What I have noticed is that if it's not on microwave, then they use digital radios in the 950 MHz MAS band which gives them sub-T1 data rates but it's good enough for what they are using it for. Most of the UHF channels are used to talk to mutual aid agencies - in this area you most frequently hear them dispatching and running checks for the railroad police.

 

[ScannerDude244]

They are still use them in Big Sur, but I know Monterey County started using starlink for a backhaul at the new site in big Sur

 

[mmckenna]

I used to be able to hear one in the Monterey Bay area many years ago, but it's long gone.

 

[bubbablitz]

Those used to be link frequencies from sites without microwave. I dont know if they are still in use but I would imagine not. I have not seen a 70mhz link radio at any site in 20+ years.

Okay, thanks everyone. By any chance, are those the big square antennas that look like big mirrors?

 

[mmckenna]

Okay, thanks everyone. By any chance, are those the big square antennas that look like big mirrors?

They were point to point, so often a Yagi antenna.

 

[ogppc]

Pacheco repeaters on 72mhz still very much active for me in Merced/San Benito counties.

 

[AM909]

Okay, thanks everyone. By any chance, are those the big square antennas that look like big mirrors?

Those are probably just directed-energy weapons. Nothing to worry about.

 

[Elpablo]

I have the two remote link frequencies for San Diego county programmed and haven't heard anything on them in years.

72.460
75.780

 

[es93546]

They used to use 72-76 MHz for radio sites that did not use commercial power. About 20 or more years ago they put microwave at a site (Sweetwater) north of Bridgeport (Mono Co.) that is only solar power with many propane tanks (at least a dozen or more) for periods of bad weather and snow. This is a key site for the northern part of Mono County, from about 8 miles north of Bridgeport to the Nevada state line. They got rid of the 70 MHz radio link that connected to the microwave site at Conway Summit. Too bad as I could hear the mobile transmission from the Sweetwater site and could hear the base reply even though I'm 50 miles south of Conway. I was just about 180 degrees south and was picking up the back signal from what I presume was a Yagi antenna pointed north.

I would imagine they did this at other sites. Even though the Sweetwater site is solar/propane backup there is now a cell phone site there. I imagine more sites around the state have constructed similar systems and that the goal is to get rid of 70 MHz altogether.

 

[AM909]

I wonder why they would use mid-band instead of UHF, though, in the case where they are trying to conserve watts. Equal power at UHF should perform better than at mid-band, especially if you consider being able to use a much higher gain antenna in the same space. Different efficiency in the link radios? Paths that aren't quite line-of-sight?