Sudbury using LRRP on VHF-Hi for vehicle tracking

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bfrederi
Posts: 129
Joined: 29 Mar 2012 15:06
Location: Burlington, MA

Sudbury using LRRP on VHF-Hi for vehicle tracking

#1 Post by bfrederi » 13 Feb 2020 17:00

I stumbled across a DMR signal on 153.1325 this morning. Turns out to be "Sudbury Water District", operating under WQXD580.

They're using LRRP for vehicle tracking which produced a nice map showing the movements of what may have been a plow.

DMR S1 DCC:4
LRRP TGID:64250

I'm not going to submit this to the Wiki until I've had more time to check out this system. I haven't caught any voice yet, and there are three other frequencies authorized under that license.

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bfrederi
Posts: 129
Joined: 29 Mar 2012 15:06
Location: Burlington, MA

Re: Sudbury using LRRP on VHF-Hi for vehicle tracking

#2 Post by bfrederi » 14 Feb 2020 14:05

With the exception of a couple of LRRP hits first thing this morning, I haven't seen any others today. (It kind of looked like the driver took the vehicle home overnight and then turned off tracking shortly after heading back into work this morning.)

I've spent the rest of the day trying to get readable voice traffic out of that system, but with no success. The scrolling DSD+ window (and the audio) indicates that there are occasional voice transmissions, but the Event log window isn't showing any hits.

I've tried both my 436 HP and several different versions of DSD+ (even breaking down and trying out FMP, in spite of my whining on another thread). No luck.

Maybe somebody with better DMR decoding/interpretation skills than mine can plug in 153.1325 and make sense out of this system.
Bruce
Burlington, MA

JBP
Posts: 156
Joined: 28 Jun 2008 11:24
Location: South of Boston

Re: Sudbury using LRRP on VHF-Hi for vehicle tracking

#3 Post by JBP » 17 Feb 2020 16:51

Just curious, what is your setup for decoding the DMR data and displaying the location information?
Jeremy
KB1REQ (DMR-MARC: 3125125)

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bfrederi
Posts: 129
Joined: 29 Mar 2012 15:06
Location: Burlington, MA

Re: Sudbury using LRRP on VHF-Hi for vehicle tracking

#4 Post by bfrederi » 17 Feb 2020 19:39

Hi @JBP --

The short answer is: the last released non-Fast Lane version of DSD+ (V 1.101), and its lrrp.exe utility.

The more complicated answer is that I stumbled across this system at the same time I was upgrading both my hardware (RTL-SDR dongle to Air Spy R2) and software (both SDR# and DSD+) so I tried a bunch of different combinations with varying results. The simplest seemed to be the most reliable: a two year old version of SDR# and the aforementioned DSD+ 1.101. AIr Spy vs RTL-SDR dongle didn't seem to make any difference, other than to complicate things. (And please don't ask me about my embarrassing attic antenna + preamp configuration. :D )

The LRRP data is actually pretty easy to capture and view -- if it's being broadcast, it just shows up highlighted in pink in the DSD+ Event Log window and automatically gets saved to a file named DSDPlus.LRRP in the installation folder. When you run LRRP.EXE in the same folder, it plots the points on a map. The LRRP UI for the map is pretty braindead -- you need to double-click a dozen times to zoom in, and pan across thousands of miles with the mouse until you get a readable display. Google Maps it ain't. But it works. Mostly. You can try twiddling with the settings in LRRP.CFG to get a sane initial display, but I usually just barrel ahead and double-click and swipe until I get a display I can read. I can post screenshots the next time I get LRRP hits.
JBP wrote:
17 Feb 2020 16:51
Just curious, what is your setup for decoding the DMR data and displaying the location information?
Bruce
Burlington, MA

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bfrederi
Posts: 129
Joined: 29 Mar 2012 15:06
Location: Burlington, MA

Re: Sudbury using LRRP on VHF-Hi for vehicle tracking

#5 Post by bfrederi » 18 Feb 2020 14:36

@JBP --

Sudbury LRRP is active today so I've taken the following screenshots FYI.
BF_LRRP_Event_log.png
BF_LRRP_Event_log.png (39.8 KiB) Viewed 70 times
BF_LRRP_map.png
BF_LRRP_map.png (189.81 KiB) Viewed 70 times
bfrederi wrote:
17 Feb 2020 19:39
... I can post screenshots the next time I get LRRP hits...
Bruce
Burlington, MA

JBP
Posts: 156
Joined: 28 Jun 2008 11:24
Location: South of Boston

Re: Sudbury using LRRP on VHF-Hi for vehicle tracking

#6 Post by JBP » 18 Feb 2020 16:01

Very Cool! Thank you for explaining it. I will have to give this a try.
Jeremy
KB1REQ (DMR-MARC: 3125125)

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