Manual Scan Decode

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tweiss3

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I came across a signal that repeats every minute and lasts for about 3 seconds, on my analog radio. I was able to set a my SDS200 on that frequency, and it does pickup the signal. Is there a way to have the SDS decode/identify what type of signal it is?
 

ka3jjz

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The way you are describing it, it's likely some sort of telemetry which the 200 won't recognize. Did you check the frequency in the FCC;s database? And what is the frequency? Mike
 

tweiss3

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I did search the FCC database, and came up empty handed with a 50 mile radius.

Its in GMRS (20) 462.675, so there shouldn't be any telemetry.
 

Ubbe

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This is what it sounds like: Copy of Monday at 4-56 PM.m4a
It sounds as a DMR signal and it's just the idle data probably from a cap+ system as non trunked DMR doesn't need to send periodical idle bursts. If you have the DMR option in your scanner you should be able to decode it when a conversation starts. You can program that frequency as a conventional frequency set to digital code search and set DND priority to it. That way you have a good chance to hear any conversations, if any, on that frequency.

/Ubbe
 

tweiss3

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It sounds as a DMR signal and it's just the idle data probably from a cap+ system as non trunked DMR doesn't need to send periodical idle bursts. If you have the DMR option in your scanner you should be able to decode it when a conversation starts. You can program that frequency as a conventional frequency set to digital code search and set DND priority to it. That way you have a good chance to hear any conversations, if any, on that frequency.

/Ubbe

Well, this isn't actually the reason I bought my SDS200 and SDS100. I do have DMR and NXDN on both. I saved it as a quick search saved, then listened the whole way home, and it didn't decode as DMR at all. Then when I got home, I ran about 30 minutes of conventional discovery on the SDS200 with logging. I got 78 hits of 0s, appears to be logging as analog, could be the data burst, but I also have 4 hits that are 1s, but they list as:
Code:
Frequency: 462.675
Date: 04/07/2021
      19:21:45
Time: 1 sec
Sub Audio: ColorCode=12

The recorded audio is just a single blip, nothing else. Does this further point to DMR? I'm going to let it run overnight and see what pops up. I'll have to terminate the discovery in the morning, wife likes to listen to the chaos that is Law/EMS radio in the area.

Being this is GMRS, is it possible someone built a repeater with some moto radios and left fleet sync or something on accidentally?
 

JoeBearcat

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Almost sounds like NXDN to me... (definitely an idle carrier)

Could be DMR.
 

sonm10

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When searching or discovering, uniden scanners don't really differentiate between analog or digital voice very well.

Now that you know that frequency is digital, you can create a scan list with that frequency and set audio type to digital
 

Ubbe

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Does this further point to DMR?
Yes. You wont get any audio from it until there's a conversation starting. If the data burst gets longer than 1-2 sec then it might be something else than just idle data. If you set the audio type to digital and not analog it will let you know if and when there's an ongoing unencrypted voice communication.

/Ubbe
 

tweiss3

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Almost sounds like NXDN to me... (definitely an idle carrier)

Could be DMR.
I honestly can't tell the difference between NXDN and DMR when listening to examples online.
Here is one more, direct recording by the SDS100 taken this morning: 2021-04-08_07-04-37.wav

When searching or discovering, uniden scanners don't really differentiate between analog or digital voice very well.

Now that you know that frequency is digital, you can create a scan list with that frequency and set audio type to digital
I see that now, I'll have to try that.

Yes. You wont get any audio from it until there's a conversation starting. If the data burst gets longer than 1-2 sec then it might be something else than just idle data. If you set the audio type to digital and not analog it will let you know if and when there's an ongoing unencrypted voice communication.

/Ubbe
Its always been between 1-4 seconds, but most of them are 1-2 seconds. I did catch a CW identifier, however, it was pretty bad reception and isn't enough to figure out a call sign. It could also be another station unrelated.

It should be noted, this morning I had 1215 hits with no information, and 3 with CC12 in 10.5 hours. This is also with the Remtronix 830B antenna, which is impressive since its still catching it in the -70db range on the scanner.

I think tonight I will put it in a list, mark it Digital only, and lock to that channel and record. I have a good 24hr window to dedicate to this, maybe I will get lucky.
 

Ubbe

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Here is one more, direct recording by the SDS100 taken this morning
It's pretty badly interfered. My experiance are that a Uniden scanner will not easily decode that signal. It needs to be just a little bit stronger with less noise. It seems that you get that stronger signal sometimes as you can get that CC12 to decode several times.
I did catch a CW identifier, however, it was pretty bad reception and isn't enough to figure out a call sign..... This is also with the Remtronix 830B antenna, which is impressive since its still catching it in the -70db range on the scanner.
-70dBm are a super strong signal that should be super clean without any noise. But it is an indication that the signal strenght comes from an interfering signal and not the DMR signal. Try to use different filter settings and IFX to get a cleaner signal. Look at the Noise level, you have to set one of the display fields to show Noise, and try to get as low Noise value as possible when selecting filters and IFX.

NXDN has a much more softer sounding datasignal than DMR, that have a more harsh sounding data that are easy to identify.

/Ubbe
 

tweiss3

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I very much appreciate all the help guys, this is my first go a discovering/tracking down a signal of this nature.

I did turn on the IFX this morning, and plugged the 100 into my computer to log via proscan, letting the scanner record the "audio". In the 4.5 hour run, it logged 248 hits, which is just shy of 1 every minute. I am seeing most all hits are 9 seconds long, some are as short as 6 seconds, but its not the typical 1s burst from CAP+ (frequency between bursts is way off too).
Now I switched filters half way through. IFX + Normal = -97db, IFX + Inverted = -104db. Duration of hit is unchanged, and I had "DMR CC12" noted in both. All recordings still are only between 1-4 seconds.
The recordings do sound a bit cleaner.

I'm going to run the second half of the day in IFX+Normal, plus turn it to digital only, to force it to decode? I will also turn the "delay" to zero.

1617985345891.png
1617985360887.png
 

Ubbe

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IFX + Inverted = -104db.
That seems to correspond more to the signal level of the received DMR signal. When trying filters and IFX you should aim for the lowest noise level and usually the weakest signal level, to attenuate the interference the most. Weak signals, especially data signals, often receives better in SDS scanners in FM mode compared to NFM.

/Ubbe
 

tweiss3

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That seems to correspond more to the signal level of the received DMR signal. When trying filters and IFX you should aim for the lowest noise level and usually the weakest signal level, to attenuate the interference the most. Weak signals, especially data signals, often receives better in SDS scanners in FM mode compared to NFM.

/Ubbe

Ok, I just swapped it back to IFX + Inverted, and changed modulation to FM from Auto.

I have had two hits with UID and TG pop up.
1617996157269.png

Also, there have been less hits overall. I will have to wait till I get home to check if there is any recorded audio.
 

tweiss3

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I just pulled the recording, and one of those DMR hits with a the TG/UID had a voice on it, only 1s long. I'm getting somewhere.
 

tweiss3

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I just wanted to say, thanks for all the help. I've learned a lot, and more about the features/filters of the SDS series scanners. I'm sure I'll forget some of it by the time I'm ready to do it again, but its good information.

I have much respect for those compiling information for the database, though, published emissions designators would cut a few steps out.
 

sonm10

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You might want to take a look here
 
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