Saturday, August 11, 2018

Unidentified Federal Trunked System A52

A quick update on the unidentified P-25 trunked sites I and others have heard in the Las Vegas area. Radio reference has updated the entry for this system and it now indicates that it is a multi-site, multi-state system, with sites in California, Arizona and Nevada.

I monitored the control channel data about a month ago on a visit to the area and it still only showed two sites active and no affiliations. But apparently they have been busy with this system build-out.

I suspect this is a Department of the Interior system that will support the Bureau of Reclamation and other DOI activities in the Lower Colorado region.

Although it is listed as "Clark, NV", I am certain that site 112 is at or near the Hoover Dam area, as I get close-call hits on that control channel when I am at the dam.

Here is what is showing at Radio Reference:

2-013     Site 13        Riverside, CA  172.1125
2-061     Site 61        Yuma, AZ       172.650
2-065     Site 65                       172.6502
2-075     Site 75                       172.1375
2-122     Site 112       Clark, NV      172.1125


Sunday, June 03, 2018

TSA Dropped 172.9000 MHz?

Back when the Transportation Security Administration (TSA) began operations in 2002, they were originally under the Department of Transportation (DOT). The radio frequencies that were first standardized to be used by the TSA nationwide included 169.3000, 172.1500 and 172.9000 MHz. These frequencies were culled from the Federal Aviation Administration (FAA) allocations, and they are still shared between the two agencies.

Since the new radio updates that the TSA has undergone, I have noted a distinct lack of any activity on the 172.9000 MHz frequency as I travel across the country. Most airports still have some activity on the 169.3000 and 172.1500 frequencies (as well as others), but mostly silence on the 172.9000. Anyone hearing activity on 172.9000 MHz, please let me know!

Federal/Military use of NXDN

   I recently saw some discussions about some VHF federal frequencies being used for an NXDN IDAS trunked system in Southern California. Monitoring had provided clues to the system users and it appears to be utilized by the Los Alamitos Joint Forces Training Center in Orange County. So far, two frequencies have been identified as being used by this system, and updates can be found here:

163.4125 MHz - LCN1
163.4375 MHz - LCN2
? - LCN3
   While the use of DMR and NXDN digital modes is increasing in the federal VHF and UHF bands, it is a bit unusual for a military facility to go with a non-standard radio system type when other military bases around the world are joining large networked P-25 digital radio systems.


Tuesday, April 24, 2018

USS Portland HYDRA System

Here is a rundown of the Portland HYDRA shipboard trunked system:

USS Portland (LPD-27)
EDACS Wide-band 
System ID – 003
397.2625         LCN-3
397.6125         LCN-5
397.7625         LCN-6
399.1625         LCN-7
399.3125         LCN-8
399.5625         LCN-9
399.7625         LCN-10

LCN-1 and LCN-2 were showing as part of the system, but were not active, so I could not confirm the frequencies. There was no LCN-4 showing.

Dockside security was using 395.2500, N293 and 398.6500, N293 for simplex communications.

   And one item that came via “close-call” near field monitoring, a UHF air band beacon on 313.6250 MHz. It was a continuous AM carrier with Morse characters “A-I-A” being send every 10 seconds. My assumption is since this vessel handles helicopters and tilt-rotor aircraft, a navigation/homing beacon to the ship would be a must.

Tuesday, April 10, 2018


A quick update on an item I posted nearly a year ago:

At the time I heard the Site 2-122 control channel on 172.1375 MHz. During my most recent trip to the Las Vegas area, I caught the control channel on 172.1125 MHz. The site is still broadcasting the same system information and using a NAC of A52.

But during my times of watching the control channel activity, I have yet to see anyone using the system. I've not seen any affiliations to this site and no voice channel grants.

The general assumption is that this is a multi-site VHF P-25 trunked system for the Department of Interior, who manages the Lake Mead National Recreation Area. And with the disbanding of the Hoover Dam Police last year, it was also assumed that the Park Police would take over patrolling the Hoover Dam and related visitors centers. That activity has not yet shown up on the new radio system.

I'll continue to monitor this system as I make it into the Southern Nevada region.

Monday, March 12, 2018

More VHF Lo Band P25?

Last year I wrote about some VHF low-band (30-50 MHz) frequencies that were heard in the P-25 digital mode. The frequencies monitored were 30.0500 MHz, 31.2100 MHz and 35.1900 MHz, all in the P-25 digital mode.

A recent posting on Radio Reference indicated that 30.1000 MHz, N270 was heard in Ohio, possibly being used by the Ohio National Guard.

The wide-band, all mode radio systems being deployed by US military units are indeed capable of P25 digital mode on nearly any VHF or UHF frequencies.

 Anyone else looking for P25 in the VHF low band? Curious if anyone else has caught any.

Thursday, December 28, 2017

New Southern AZ Finds

While visiting family in the Tucson area over Christmas 2017, I came across some new to me federal VHF channels in use. These include 2 new DMR VHF federal channels that I have not been able to determine who the user is yet.

168.7750 MHz DMR - Color Code 12, Time Slot 1
All conversations heard on Talk Group 111, so not part of a trunked system. All transmissions were encrypted.

169.3750 MHz DMR - Color Code 12, Time Slot 1
All conversations heard on Talk Group 122. Radio IDs were not the same as seen on 168.7750 MHz. All transmissions were encrypted.

   I'm not certain who these belong to. I had heard some analog traffic on the 168.7750 frequency in past years, but never identified who the user was. The frequencies themselves have been associated with the Department of Agriculture and the US Postal Service. My bet it probably on the USPS at some central mail facility in Tucson. Why they enabled the encryption is beyond me.

And as I was searching I came across two more CBP repeaters that I have not logged in my past visit:

169.8875 MHz, N208
173.9375 MHz, N304

Both carried encrypted traffic with the normal CBP radio identification ranges.

Thursday, December 07, 2017

CBP Captures Smugglers TRBO Radios

A recent posting by Customs and Border Protection (CBP) reports the capture of a group smuggling marijuana across the southern Arizona border with Mexico. The Yuma Sector was involved in the arrest:

Photos that accompanied this report on the CBP Twitter feed showed the radios and batteries that were seized during this arrest.

The CBP photo shows several models of Motorola TRBO digital radios, probably UHF. I'm wondering if they will do any forensic radio analysis and see what frequencies they were on.

The drug cartels in Mexico have long been known to use radios, and not just portables. A while back, there was a wide-area radio system with linked repeaters that was reportedly build by a company in Houston, Texas. It was operating in an unusual part of the UHF military air band and was fully encrypted, of course.

Which brings me to a recent discovery when I was in Arizona. I left my radio searching unattended while parked at a fairly high altitude near the Mexican border. I recorded a number of encrypted DMR hits on unusual UHF frequencies. I caught quite a bit of traffic on 403.2500, 403.3500 and 403.4500 MHz. All the communications I recorded were using the same talk group number (116), so this might be part of a trunked system. Is this really related to drug smugglers? Who knows, but an interesting catch none the less...