DMR beacons on 467.5375 and 467.5625 (FRS 8) channel in Long Beach

Status
Not open for further replies.

Mikek

Member
Premium Subscriber
Joined
Jan 10, 2003
Messages
268
Is anyone else picking up a DMR base station beacon on these channels? Color Code 1, in the Long Beach area? So far, no voice traffic, just the beacon every 30 or so seconds.... both channels are identical in timing and data content.
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
5,784
It sounds illegal as heck, especially on the 467 frequencies.

The FCC did a bonehead move about 2 or 3 years ago and permitted incursion into the guard band at the lower and upper channels of the 462 and 467 MHz GMRS part 95 spectrum by Part 90 licensees. However the modulation was supposed to be narrow NXDN. unfortunately the GMRS community was lulled into thinking this was OK and raised no objection. A similar proposal was made to overlap BROADCAST auxiliary freqs at upper 450 MHz and was dismissed by FCC for all the appropriate reasons.

It would be valuable to determine who is transmitting on the channels you indicate.
 

buddrousa

Member
Premium Subscriber
Joined
Jan 5, 2003
Messages
10,360
Location
NW Tenn
I would think it is more of a bonehead wanting their own private radio system and does not care about anyone else.
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
5,784
I got involved in some narrowbanding for a college part 90 system and the client relied on 3 different radio shops for services . I found they had dozens of unlicensed frequencies in the radios and even an unlicensed repeater at 300 ft AGL at a downtown location. In consulting with the coordinator I was told this is common on the business frequencies and advised we monitor the band for clear freqs and request them. I told them nope, to coordinate with what was licensed and we would report anyone found on our new freqs to FCC. Weird that the coordinator accepted this as status quo.
 

prcguy

Member
Joined
Jun 30, 2006
Messages
13,460
Location
So Cal - Richardson, TX - Tewksbury, MA
I hear it and the .5375 signal is about 12dB stronger than the .5625 signal. They appear to be identical and I think the .5625 might be Intermod or something unintentional. I think it might be SCADA or some other kind of data transmission.
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
5,784
I hear it and the .5375 signal is about 12dB stronger than the .5625 signal. They appear to be identical and I think the .5625 might be Intermod or something unintentional. I think it might be SCADA or some other kind of data transmission.
You might look up the FCC website to see if a company called MRC or similar has licensed it in your area. The emission designator was supposed to be 4K something , but if it is a DMR beacon they have constructed beyond so what the FCC permitted. I don't recall if the channel center was to be at 6.25 or 12.5.

I was pissed that the FCC allowed this and now nationwide. originally the FCC said they would not allow Part 90 to overlap Part 74 because it was a long standing rule not to cross over band assignments as well as citing strong technical objections. Now they have ignored their own good logic and allowed Part 90 to overlap Part 95. The GMRS community I reached out to at the time were ignorant of the technical reasons to have a sliver of guard band. Problem now is that GMRS operations are no longer licensed by site, so proving incumbency requires record keeping that may not exist and engaging lawyers. So the 800 lb gorilla wins again.
 

Mikek

Member
Premium Subscriber
Joined
Jan 10, 2003
Messages
268
No FCC listings for LA or Orange County for those channels - and it's definitely 2-slot DMR (not scada). No CWID. I'll leave the TRX1 recording on it for the next few days I'm here to see if I get any voice traffic.
 

kj6psg

Member
Joined
Sep 1, 2012
Messages
182
Location
Ventura, CA, USA
I've been hearing this for years (at least since 2017) and thought I was going crazy! It comes in really, really weak over here, but gets stronger at times. I've heard it on a handheld once. It's definitely not a repeater running out of some guy's garage if it's heard in both Long Beach and Ventura. I think 467.5625 came in stronger here but I'd have to check again. I've never heard anything beyond just the DMR idle bursts. Can't remember the color code either.

[edit] Reviewing logs from December 2017, I had 467.5625 logged with -115dBm signal strength on roof antenna (dipole w/ no gain), with color code 1. No traffic logged over the three-day monitoring period.
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
5,784
Listen 5 MHz up and 5 MHz down, but also +/- 10 MHz. Motorola was selling some small low cost commercial market repeaters that had some odd splits to accommodate cheap ceramic duplexers and they were trying to get an FCC waiver to permit this. There are some Chinese products as well trying this.

Also don't discount an IF image because it could be an amateur radio hot spot around 446.
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
5,784
I'm hearing them right now, they're quite strong (-80dBm on 467.5375 MHz, -103dBm on 467.5625 MHz) with slow but significant variation. Just a beacon, no voice or anything. Both key up at the same time and send the same data. Nothing around it to indicate intermod.
Road trip?
 

prcguy

Member
Joined
Jun 30, 2006
Messages
13,460
Location
So Cal - Richardson, TX - Tewksbury, MA
I see the post where avascan522 will be looking from Catalina and that brought up an idea. If the source were on Catalina, that would not only explain the large coastal area of CA being affected, it would also answer for the slow variation in signal level. The Catalina to mainland path is notorious for multipath fading.

Otherwise I can't think of any mainland hilltop that would cover coastal LA county and Ventura at the same time on UHF.

I'm hearing them right now, they're quite strong (-80dBm on 467.5375 MHz, -103dBm on 467.5625 MHz) with slow but significant variation. Just a beacon, no voice or anything. Both key up at the same time and send the same data. Nothing around it to indicate intermod.
 
Last edited:

kj6psg

Member
Joined
Sep 1, 2012
Messages
182
Location
Ventura, CA, USA
About two days ago, I was receiving it again; 467.5625 stronger than 467.5375 this time. Could it be ship-borne? There's a really wide variation in signal strength over long periods of time, so I would suspect it's not a stationary transmitter at all. I recall hearing it in Santa Paula at one point (2018ish) as well.

Hopefully when the machine shop reopens, I'll be able to finish up my RDF setup.
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
5,784
About two days ago, I was receiving it again; 467.5625 stronger than 467.5375 this time. Could it be ship-borne? There's a really wide variation in signal strength over long periods of time, so I would suspect it's not a stationary transmitter at all. I recall hearing it in Santa Paula at one point (2018ish) as well.

Hopefully when the machine shop reopens, I'll be able to finish up my RDF setup.
Big ship, two repeaters, bow and stern? It turns, they vary. They are linked via IPSC?
 
Status
Not open for further replies.
Top