We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.

Author Topic: 151.625 MHz Business Band Itinerant Analog FM vs. DMR Digital Voice 12 Feb 2020  (Read 1053 times)

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
Around 12:30 PM local time, receiving equipment is a TYT TH-9000D VHF mobile transceiver with a Browning BR-168-BS 1/2 wave VHF antenna with a Chevrolet sedan ground plane.  Tuned to 151.6250 MHz listening to two different users running analog FM (narrow FM, NFM, NBFM) 11 kHz bandwidth analog voice, one of the users appeared to be a construction crew and the other sounded like surveyors.  A strong DMR signal (full scale) obliterated the analog traffic on frequency for several seconds at a time.  I've noticed multiple analog users of the VHF itinerant business frequencies, but 151.625 MHz is the only one I've heard DMR digital voice on.  It's not P25, but DMR aka Motorola TRBO or MotoTRBO.

VHF itinerants:

151.5050 MHz
151.5125 MHz
151.6250 MHz
151.7000 MHz
151.7600 MHz
154.5275 MHz
158.4000 MHz
158.4075 MHz

151.625 is by far the most popular of the eight frequencies.  If you include the five license-free MURS channels 151.820 MHz, 151.880 MHz, 151.940 MHz, 154.570 MHz and 154.600 MHz along with 151.955 MHz (which isn't technically an itinerant channel), the number of monitoring targets increases significantly. 
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Josh

  • DX Legend
  • ******
  • Posts: 4079
  • Karma: +12/-19
    • View Profile
Could be cops doing a stakeout.
We do not encourage any radio operations contrary to regulations.

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
Could be cops doing a stakeout.

They're partial to UHF and 700/800 MHz  - plus now their 800 MHz trunking system is 100% encrypted.  Prior to the switch over to 100% encryption I could hear all the "tac" talkgroups (channels) - which were (and probably still are) heavily used as "party line" channels for various task forces, generally associated with narcotics and vice cops, often with informal CB-like chatter and very personal information being shared over the air.  One time they had a patch from what sounded like an analog wire or surveillance feed re-transmitted over one of these tac channels so that the "roving" officers outside the short range of the wire/bug could hear the audio. 

There's a massive demolition project going on in the downtown area, with several contractors and subcontractors involved...I caught a glimpse of one of the radios being used and it had a distinctively VHF antenna.  Compared to most on-site construction radios (which are UHF) it was noticeable.  I was driving by and didn't get that good of a look at the radio but it was a Motorola and probably a MotoTRBO model, which would explain the DMR traffic heard on 151.625 MHz.

One of the subcontractors ( https://www.radioreference.com/apps/db/?fccCallsign=WPNU205 )  uses 151.6250 in addition to 151.5050, 151.5125, 158.4000 and 158.4075.  They use 151.625 as their truck-to-truck channel, with very high power mobiles.  They use analog only though. 

U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Σ

  • Blog author
  • Sr. Member
  • *
  • Posts: 331
  • Karma: +8/-5
    • View Profile
    • ΣSDR KiwiSDR online
You would be surprised how many "reputable" radio shops will just program just any licensed itinerant into radios just to sell them. With DMR being affordable, now you have a "private channel" so no one can eavesdrop on you. I have heard these sales pitches relayed to me many, many times from clients who have come to me looking for advice. Most times these shops neglect to tell people they need licenses, too.

151.625 does appear to be one of the free-for-all frequencies. Power up to 100 watts is allowed.
- Rob

CT/MA border
Afredri SDR-Net with multiband dipole at 65 ft.
Email: commsigma@gmail.com
KiwiSDR online - http://sigmasdr.ddns.net:8073/
ΣSDR Blog - https://n1nte.blogspot.com/

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
Yep.  151.625, 151.955 and several others are included as the default out of the box channels for Motorola and Kenwood land mobile gear.  They’re basically the VHF versions of 464.500, 464.550, 467.925, 467.875, 467.850, 469.500, 469.550, etc.

DMR is affordable and encrypted DMR is relatively easy to implement.  Lots of users (construction companies included) seem to simply buy a massive lot of radios and use them on the factory default channels.  I know that local radio shops will often leave the radios on the factory default channels but change the CTCSS or DCS tone/code. 

For the end user, that turns into a “private channel”.  Same thing with DMR.

Crane Master - who is actually licensed for 151.625 among others, make extensive use of that frequency (with a PL tone, 167.9 Hz to be exact) for truck to truck chatter.  They’re licensed for 110 watts on 151.625 but only 45 watts on the other VHF frequencies on their license.  From what I’ve heard of them using 151.625, they are running 110 watts...

I’ve seen licenses authorized for a lot more than 100/110 watts on 151.625 and others.  I believe the American Red Cross is licensed for 110 watts PEP -on 151.625 and several other channels - base stations, mobiles and portable/temporary repeaters.  Similar licenses for temporary / itinerant systems exist with similar power levels....or even more than 110w.  Highest I’ve seen is 300w. 

The ARC is also authorized 125w PEP (500w ERP) on 27.490 MHz as part of the same license - WQMD985

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=3214188


Here’s another interesting one. 

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=4215560

« Last Edit: February 13, 2020, 2210 UTC by R4002 »
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
Just another update: 

Heard some more very strong DMR traffic on 151.625 this morning, along with some weak analog FM voice.  023 DCS code along with 67.0 Hz, 94.8 Hz, 97.4 Hz and 136.5 Hz CTCSS tones have been logged in the past.  I know the film school for the local university uses 151.625 and 151.955 for camera crew comms and other purposes.  I've logged them as using both 67.0 and 94.8 PL tones.  Unfortunately there's also a local funeral home that uses 151.625 with 97.4 Hz PL tone, and of course Crane Master doing 110 watts with 167.9 Hz PL.

I found the listing for the default factory frequencies for the Motorola RDX series RDV5100 VHF radio:

Channel 1 - 151.6250 MHz - 67.0 Hz PL
Channel 2 - 151.6250 MHz - 77.0 Hz PL
Channel 3 - 151.6250 MHz - 88.5 Hz PL
Channel 4 - 151.6250 MHz - 179.9 Hz PL
Channel 5 - 151.6250 MHz - CSQ - carrier squelch (no PL or DPL)
Channel 6 - 151.9550 MHz - 67.0 Hz PL
Channel 7 - 151.9550 MHz - 82.5 Hz PL
Channel 8 - 162.4000 MHz - CSQ - RECEIVE ONLY - "WC" (Weather Channel)
Channel 9 - 151.9550 MHz - 179.9 Hz PL
Channel 10 - 151.9550 MHz - CSQ - carrier squelch (no PL or DPL)




Here are the "27 business exclusive" frequencies available for the Motorola RDX and RDV VHF radios (and others, including the Kenwood TK-2400 series radios such as the TK-2400VP)

Frequency 01: 151.6250 MHz - itinerant
Frequency 02: 151.9550 MHz
Frequency 03: 152.8850 MHz
Frequency 04: 152.9150 MHz
Frequency 05: 151.7000 MHz - itinerant
Frequency 06: 151.7600 MHz - itinerant
Frequency 07: 152.9450 MHz
Frequency 08: 151.8350 MHz
Frequency 09: 151.8050 MHz
Frequency 10: 151.5125 MHz - itinerant
Frequency 11: 151.6550 MHz
Frequency 12: 151.6850 MHz
Frequency 13: 151.7150 MHz
Frequency 14: 151.7450 MHz
Frequency 15: 151.7750 MHz
Frequency 16: 151.8650 MHz
Frequency 17: 151.8950 MHz
Frequency 18: 151.9250 MHz
Frequency 19: 152.9000 MHz (incorrectly printed in some Motorola manuals as "152.7000 MHz")
Frequency 20: 154.4900 MHz
Frequency 21: 154.5150 MHz
Frequency 22: 154.5275 MHz - itinerant
Frequency 23: 154.5400 MHz
Frequency 24: 153.0050 MHz
Frequency 25: 154.5475 MHz
Frequency 26: 158.4000 MHz - itinerant
Frequency 27: 158.4075 MHz - itinerant


The Motorola RMM2050 (MURS radio - license free, but sold as an on-site business radio)

Defaults to:

Channel 1 - 154.5700 MHz - 67.0 Hz PL
Channel 2 - 154.6000 MHz - 67.0 Hz PL
Channel 3 - 151.8200 MHz - 67.0 Hz PL
Channel 4 - 151.8800 MHz - 67.0 Hz PL
Channel 5 - 151.9400 MHz - 67.0 Hz PL

Motorola also identifies frequency 1 as 154.570 MHz, frequency 2 as 154.600 MHz, frequency 3 as 151.820 MHz, frequency 4 as 151.880 MHz and frequency 5 as 151.940 MHz.
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline ThaDood

  • Hero Member
  • *****
  • Posts: 568
  • Karma: +8/-2
  • There
    • View Profile
    • Extreme Part #15!
    • Email
Whenever I see the commercial tower climbing contractors going up and down that 600ft TV tower, about 1 mile from where I am, I hear all their COMM's on 151.625MHz NBFM. Makes me wonder just how far they're being heard from up there.
I can't decide upon what's worst, young and stupid, or old and chemically dumbed down.

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
They’re probably getting some pretty insane range if they’re 400-500-600 feet above ground level. 

Assuming they’re using 4-watt or 5-watt handheld radios...it wouldn’t surprise me if their signals are making it 40-50+ miles from that high up (depending on the terrain of course).

I know there's a low power (~4 watts transmitter power, ERP is probably about 8 watts) simplex repeater installed in the downtown area of the city I live in...it's on MURS channel 2 - 151.880 MHz - and the antenna is maybe 30 feet above street level.   Even with that modest height and power level, it can be heard 5 miles away....and this is in an urban area with lots of obstructions.

I've monitored what sounded like either RF engineers or IT installation guys installing antennas of some sort in a high-rise building, they were talking about coax cable runs, antennas, filters and the like.  They weren't on VHF, they were on one of the UHF itinerant business band frequencies (specifically 469.500 MHz).  From their conversation it was obvious that they were either on the roof of the building or on the top floors.  They were very strong for several miles away from the downtown area, even with QRM from other business users on the same frequency.  Lucky for them they were running a DCS / DPL code and weren’t suffering any sort of QRM.

Height is key.  It wouldn't surprise me if the tower climbers on 151.625 MHz you're talking about cause at least minor amounts of QRM to all sorts of users dozens of miles away from them. 
« Last Edit: February 17, 2020, 2157 UTC by R4002 »
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Σ

  • Blog author
  • Sr. Member
  • *
  • Posts: 331
  • Karma: +8/-5
    • View Profile
    • ΣSDR KiwiSDR online
There is a local hot air balloon company that also uses 151.625 to coordinate the chase vehicle. LOTS of range from the balloon.
- Rob

CT/MA border
Afredri SDR-Net with multiband dipole at 65 ft.
Email: commsigma@gmail.com
KiwiSDR online - http://sigmasdr.ddns.net:8073/
ΣSDR Blog - https://n1nte.blogspot.com/

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
Like standing on top of a several hundred (or thousand) foot tower with a HT.  Love it. 

It would be cool to go up in a balloon with a handheld CB with a halfway decent antenna. 

I’ve done some basic range testing on 2 meters and the 151 MHz / 154 MHz MURS frequencies (they have the same propagation characteristics) with another op in his mobile...I parked on top of a hill roughly 200 feet above the floodplain and low-laying area and alternated between 10 watts, 25 watts and 70 watts on with my mobile radio and 4 watts on my handheld.  Only when you get to the fringe of the 4 watt/10 watt range does having the high power capability make the difference.

Would love to do a side-by-side with 11 meter AM and VHF high band (2m or MURS) with the same power level range test. 

Of course these have been done in mostly urban areas with lots of obstructions...

In most areas, rural and urban, the proliferation of data link and telemetry systems on the MURS channels make fringe-range operation more annoying.
« Last Edit: February 17, 2020, 2204 UTC by R4002 »
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline R4002

  • DX Legend
  • ******
  • Posts: 2608
  • Karma: +1/-0
    • View Profile
The DMR users on 151.625 have moved at least one of the other groups off 151.625 MHz and on to 151.505 MHz.  Strong analog FM voice on 151.5050 MHz
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers