Nelson County, VA Police & EMS Go Digital

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thstaff

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On 12-10-14 Nelson County EMS and law enforcement changed to digital narrowband radios. Perhaps added an extra channel or two. Does anyone know if this is standard APCO 25 format digital and what the frequencies are?

I am hearing what I think are the digital streams, but they aren't decoding even a proper receiver.

Radios used are probably Mototola XTS series
 

popnokick

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There are a slew of frequencies listed in the FCC ULS under a recent modification that was Granted, and another batch that appear to have been part of an emergency STA. It will require some frequency searching if you're in the area to figure out what's what.
 

GmanX

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Im pretty sure it is plain jane motorola p25 digital
 

n4jri

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It's P25. Hearing the sheriff on 159.15 [NAC200], but also hearing what might be some masking. Heard a fire or rescue conversation on 155.6175 [NAC200] talking about something at the south end of the county. Reception was a more difficult than I'm used to and it makes me wonder if it's related to simulcasting or multipath. Heard more on these freqs while in Albemarle and Buckingham than while in Nelson.

Another interesting thing is that 159.15 is a voice freq on one of the STARS sites, so you'll hear what might be better-sounding P25 voice on that with a 190 NAC.

73/Allen (N4JRI)
 

QDP2012

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There are a slew of frequencies listed in the FCC ULS under a recent modification that was Granted, and another batch that appear to have been part of an emergency STA. It will require some frequency searching if you're in the area to figure out what's what.
A list of FCC Licenses/Callsigns and their related frequencies has been added to the Nelson County (VA) Wiki page.
If any are missing, please update here or there.

Hope this helps,
 

thstaff

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Yeah, getting the main sheriff dispatch on 159.150 - standard P-25 as noted above. (can someone explain what the NAC means?) Rescue calls are still being dispatched analog on 155.865 and I hear some two way traffic there, but then I also discovered some digital rescue traffic moved to 158.850. I still haven't found that I think is the (new) regular main two way radio traffic channel for rescue.

Found at least one input side for rescue that was very strong on 155.520 which I don't see listed so far.

From what I can gather this is a simulcast system with microwave hops across the county to connect them all.

Wintergreen Rescue did not go digital but do have radios capable of talking with Nelson as needed to coordinate. Both Wintergreen Fire & Rescue along with Wintergreen Police remain analog.

I am searching some of these newly mentioned frequencies reference above in this thread.

Appreciate everyone's feedback and input thus far!
 

n4jri

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I believe it stands for Network Access Code. Acts like PL for digital stuff, but a little more sophisticated. The PSR500/600 and their various clones read these codes when receiving the frequency. It'll also read them on Motorola or P25 digital trunked systems. STARS voice transmissions show NACS ranging from 190 to 19F, for example.

So if you set your NAC to 200 for the Sheriff, it'll reject stuff from STARS that's on the same frequency, with the 190 NAC.

If the system is simulcast, that may explain the transmissions not tracking well on our radios. Getting multiple sources of the same thing on the same freq. Contrast with STARS sending out P25, but on a different freq from each site.

I was hearing something digital on 158.73, but that might be Greene Co. Are you sure about 155.52? I thought Amherst was using that for a simulcast. (PL 192.8, maybe?)

73/Allen (N4JRI)
 
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thstaff

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Allen,

You are probably right on that being Amherst. I heard them making a call that was southern Nelson. That was probably a mutual aid to Nelson out of Amherst.

Thanks for answer the question on the NAC.

Appreciate!
Tommy
 

kb4cvn

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Nelson's Migration to P25

...Found at least one input side for rescue that was very strong on 155.520 which I don't see listed so far.
Don't forget, Amherst County Fire/Rescue still pages on 155.52000 with a tone of 192.8 Hz. This is simulcast with dispatch traffic on the EDACS 'FD DISP" (Fire/EMS Dispatch) talkgroup of 273.

Last time I checked on 155.52000, it was still an operational repeater, with the input being: 156.09000 MHz (192.8 Hz). For background, this is the old Sheriff Department repeater, which apparently they kept in place after the County's migration to EDACS in 1998.

I only became aware of this change last night. I am going to load all the new frequencies into a M7100 mobile while running errands today (Wed. 2014-12-17), and I will post the results this evening.

My location is in Northern Amherst County, and I can hear most traffic, even on the inputs from Nelson County if I swing the yagi in that direction.
 
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kb4cvn

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Network Access Code (NAC)

"...can someone explain what the NAC means?

In its simplest form, the NETWORK ACCESS CODE (NAC) is the digital equivalent of a subaudible tone (CTCSS, Quiet Channel, Channel Guard, Private Line, etc.).

In Analog mode, a CTCSS tone or Digital Squelch codeword (DCS, Digital Channel Guard, Digital Private Line, etc.) is transmitted with the audio to open receivers on another radio, or a repeater's input.

In non-P25 Digital mode, due to their not being any Analog component to convey the subaudible component (analog tone or digital codeword), a digital address code is transmitted once a second in the data stream to accomplish the same task. In GE radios (now owned by Harris), this was referred to as the "TX and RX Address". Transmit and Receive codes can be different!

An example would be a fire department who had two repeater sites, one east and one west, on the same input and output RF frequencies. Both repeaters therefore could have the same output RF frequency and digital address (or CTCSS/DCS if analog), and could have the exact same input RF frequency, but have a different digital address (or CTCSS/DCS if analog) so the users could selectively access either repeater site. This is very common in state forestry systems.

In P-25 Conventional digital systems, the NAC code is transmitted continuously as part of the preamble in the message data superframe. NAC code function for conventional P-25 and trunked P-25 systems are quite different. The DEFAULT NAC code for conventional P-25 is $293 (hex 293), and is often used for Amateur Radio repeaters. Using the default for commercial or public safety systems is not a wise decision, as it is the digital equivalent of Carrier Squelch.
 

QDP2012

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...Found at least one input side for rescue that was very strong on 155.520 which I don't see listed so far....
Don't forget, Amherst County Fire/Rescue still pages on 155.52000 with a tone of 192.8 Hz. This is simulcast with dispatch traffic on the EDACS 'FD DISP" (Fire/EMS Dispatch) talkgroup of 273.

Last time I checked on 155.52000, it was still an operational repeater, with the input being: 156.09000 MHz (192.8 Hz). ...
An FCC search for 155.520 lists only the following Amherst license, none in Nelson. Other licensees are elsewhere in the state.

KNAG560: Amherst County -- 155.520 / 156.090

Hope this helps,
 

kb4cvn

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Wednesday Log on Nelson

Monitoring observations on Nelson’s new system.
First of all, from vantage point operating mobile near Lynchburg, it was an effort to monitor the new P-25 traffic due to other P-25 traffic present on the same frequencies (159.15000 & 155.61750).

Never heard a peep on the analog Fire repeater (155.86500 w/167.9 Hz). But I did hear a couple of dispatches over on 155.61750 (NAC 200).
Copied Sheriff traffic on 159.15000 (NAC 200), but the interference from STARS was frequent and quite annoying. The only STARS site I could locate on this frequency is located in Salem, VA (WQMG581 37-20-23.6 N, 080-04-13.6 W).
One other issue I encountered was self-inflicted. I had enabled the receiver pre-amp (12 dB). I did bring the laptop with me and shut this off the first chance I had, thereby resolving some, but not all of the on-frequency interference from other agencies.
From a couple of transmissions monitored, I am guessing that 153.92000 is the input to 159.15000.

The LID for the Dispatcher is “911”.
Several Sheriff Deputies I monitored and had a chance to write down their ID and LID number were:
323 = LID 10007
310 = LID 10019
I have other LID numbers, but did not get the chance to write down the user ID’s. Kinda hard to do and drive. But, it looks like 10,000 series LID numbers are most likely a block for the Sheriff. I am fond of tracking the active LID numbers, and using the ALIAS function to have the radio display each user’s alpha-numeric radio ID, rather than the raw LID number.

On Thursday my plan is to have the radio decode on the NAC and Group number, which I am assuming at this point as being 00001. This should mitigate some of the false decoding of STARS.

I had the following frequencies programmed:
155.86500
155.61750
153.84500
153.87500
153.92000
153.96500
153.98000
154.99500
155.76000
155.95500
156.01500
159.15000
155.67000
154.72500
155.97750
158.85000


But only copied traffic on:
159.15000
153.92000
155.61750
 

thstaff

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Thanks Mark for the update. I've noticed tons of interference on that 159.15 freq for the Nelson SO as well. Why would they ever have that freq so closely related to STARS?

Tommy
 

n4jri

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Nelson was obviously there first. Not sure how STARS got to have it where it would be heard so strong in Nelson. It would be interesting to confirm what STARS CC is being used when 159.15 is the VC. I didn't think to do this when I was there.

73/Allen (N4JRI)
 

kb4cvn

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Friday update:
Adding in the talkgroup (GID 00001), and requiring the radio to decode BOTH the NAC ($200) and the Talkgroup (GID 00001) solved the undesired unmute issue.
But, the radio is still stopping on the memory channel everytime a working channel assignment occurs on the STARS site in Salem. See if I can figure out a programming tweak to help resolve that.
BTW: Depressed the monitor button a few times and copied STARS traffic related to Red Onion prison and VSP calls out on I-81. Being outside Nelson County and mountain topping like a am most of the time, I can routinely copy UHF and 800 traffic from Salem and Roanoke, and even Blacksburg on occasion. I would assume listeners in Lynchburg or Bedford would have the same issue I am seeing.

Regarding the co-channel usage… Yes, Nelson was there first. Operations within the confines of Nelson County should not be an issue for their units. That is, until you have a Tropospheric band opening or local enhancement. That could cause the folks in Nelson some major grief. Yes, capture effect would still allow them to communicate. But I doubt they would be able to scan with an active signal for the radio to lock onto. Time will tell.
 

kb4cvn

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New Nelson Info on system, and issues

Noticed tonight over on Wintergreen Fire/Rescue's facebook page, some complaints about the new system, and an audio recording of just how bad the system sounds to the users.

==========================

Nelson County new radio system.
Hear how wonderful it is here https://www.facebook.com/WintergreenFireRescue


==========================
Gee, it sounds that bad INSIDE of Nelson County. Ditto with the Sheriff's new digital channel.

I hear it the same way down (distorted with a high Bit Error Rate) here in Amherst County (Elon and Madison Heights areas). I assumed it was because I was outside of the coverage area!

Before I retired from the two-way radio industry after 32 years, I had designed and installed several new P-25 systems. They should NOT sound this bad if they were designed properly.
 

thstaff

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Mark, I too oversaw the design and installation of a similar system back in W-TN. In the late 1980's. We were doing digital encryption but analog normal. Wide band in those days. Not apples and apples. But similar because we used a complex digital encryption Motorola DVP back then. Similar to DES. Once it was set right, finally, it worked beautifully.

Here in Nelson (lay terms) it simply doesn't appear to be decoding properly. Why I don't know. I now know they have 3 sites all linked by MW and the sites listen for and assign the best transmitter to handle the traffic. All traffic is simulcast over all three xmitter sites.

The complaints you are reading about Wintergreen are valid. At first I thought not. But on a rope rescue they had Saturday at Crabtree Falls, I actually had a fully programmed WFD portable to monitor and did side by with my Uniden XLT. The Uniden picked up and decodoed properly. I heard zilch on the WFD portable. That IMHO appears to be a programming issue, I think.

And they definitely have two weak areas of the county. Northern Afton and the Roseland / Massies Mill areas. The previous analog system covered them easily. The digital narrow band sites, as you well know, aren't as forgiving.

I have actually been asked (due to prior experience back in TN) to evaluate and see what I think. They definitely have deficiencies. The remedy. Remains to be seen.

T
 

kb4cvn

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Excellent points. With just three transmit sites (Devil's Knob@ Wintergreen, Sugar Loaf Mtn. & High Top Mtn.), the terrain of Nelson County would be a challenge with all the mountain coves and shading.

I would have expected them to add at least one additional site atop Tobacco Row Mtn. (Aka: High Peak) in Amherst County with antennas patterned to favor Nelson County to fill some gaps in the NW quadrant and the area between Highway 60 and Highway 56.

As far as mobile and portable talkback, a few carefully placed satellite receivers would improve the coverage issues in the areas you mentioned (Afton, Roseland, Massies Mill), and could be backhauled to either Devil’s Knob or if a LOS path exists, directly back to Lovingston on a digital 900 link.

The cost figure for the new system I saw mentioned ($3M) seemed to be a bit light to me for all of the user terminal radio AND the new digital infrastructure.

I know all too well rural community’s budgets are tight. Even worse in this economy. I wonder if migrating both LEO’s and Fire/EMS together was a good idea. The better solution might have been to only move one at a time, “get the bugs” worked out regarding terrain and coverage before going to a second phase and moving the remaining emergency responder groups.

I would love to see a copy of the projected talk out and talk back coverage maps. Since I retired in 2012, I don’t have access to radio coverage plotting software (RAPTER, etc.) any longer.

My humble 2-cents worth.
 
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