220 MHz SMR in OKC

[Gilligan]

While I was at work last night, I decided to try searching 217 to 221 MHz. I've never paid hardly any attention to that band, so I figured I'd give it a shot and see if there is any activity. I worked from 11pm to 7am so I didn't count on finding anything. What I did find was actually kind of surprising.

My 246T locked onto what sounded like a data channel on 220.000. I listened to it for several minutes, then just as I was about to lock it out, I heard a callsign. After several attempts, I copied the callsign as WPCX25. A quick search through the FCC database yielded the license WPCX255 for United Telecomm in OKC. It is apparently a "non-nationwide 5 channel trunked, 200 MHz license." Five frequencies starting with 220.0025 and incrementing 150 KHz each. The emission types for all frequencies are both analog voice and digital w/ subaudible tone (probably SMR control). The transmitter location is at 1700 S. Missouri in OKC. 500 mobiles are on the license with channels 1 KHz above the base channels.

Has anyone ever heard of SMR on 220 MHz? My 246T allowed my to plug the freqs in for LTR but rounded them off. Of course, it doesn't sound to me like an LTR system. There are no data bursts, just a steady control channel until the callsign in Morse. Give a listen and maybe someone can identify what exactly this is. I'm also curious to see if any voice activity shows up during the daytime.

 

[EricCottrell]

Hello,

217 to 218 MHz is used for the Automated Maritime Telecommunications Service. The FCC opened the service up to Land Mobile as well. There are systems on the coasts and some inland locations. The systems in the Northeast tend to use Passport LTR. The FCC has auctioned off frequencies in this service nationwide. NBFM is used with a 12.5 KHz channel spacing.

220 to 221 is more complex. It originally was a band for very narrowband modulation methods. There are trunked radio systems that use Amplitude Companded Sideband (ACSB). You can listen to the voice on Lower Sideband but there is a 2 KHz pilot tone that can be annoying.

Recently the 5 adjacent frequencies used for ACSB can be converted into 2 NBFM channels. Boston has both ACSB and FM systems. The FM system in my area uses Passport LTR. To listen you need a radio that can do a 6.25 KHz step as the frequencies are 220.00625, 220.01875, 220.03125, etc.

73 Eric

 

[kb5udf]

Might be MPT-1327 Trunking

I think MPT-1327 can be used in this band. Checkout this link http://www.kb9ukd.com/digital/. You can compare the control channels there to what you are hearing.