Close Call and DMR

[pb_lonny]

I have a couple of local radio users who have switched to what I believe is DMR (this is based on the audio samples I provided.)

I can recall reading that Close Call does not work with DMR as the signal duty cycle is too short to trigger Close Call, yet I am getting multiple Close Call hits on one frequency in particular which makes me think it might not be DMR. Is this correct?

 

[racingfan360]

Close Call will not detect on a DMR Simplex or Uplink channel. It will detect the Downlink (Repeater) channel (in fact all Uniden scanners will close call on the Repeater signal - it's not just limited to the new DMR-capable scanners).

If you record and upload an audio sample of the raw signal, I can likely help you understand what type of transmission it is. Alternatively, this site might help: http://www.sigidwiki.com/wiki/Digital_Mobile_Radio_(DMR).

 

[toastycookies]

Close Call will not detect on a DMR Simplex or Uplink channel. It will detect the Downlink (Repeater) channel (in fact all Uniden scanners will close call on the Repeater signal - it's not just limited to the new DMR-capable scanners).

If you record and upload an audio sample of the raw signal, I can likely help you understand what type of transmission it is. Alternatively, this site might help: http://www.sigidwiki.com/wiki/Digital_Mobile_Radio_(DMR).

Why won't close call detect a "DMR Simplex or Uplink channel"

This makes no sense.

 

[racingfan360]

Why won't close call detect a "DMR Simplex or Uplink channel"

For close call to work, it needs to a relatively strong signal (I think it needs about +15dB higher than the local noise floor) but it also needs the signal to be present for a sufficiently long period of time for the scanner to latch onto it. I think the DMR single slot TDMA frame is only around 30ms long, and that's too short for Close Call to work. The repeater signal uses two slots interleaved, and that is sufficient for Close Call to work.

 

[UPMan]

The above description is dead-on.
Close Call details are in the patents:
https://patentimages.storage.googleapis.com/pdfs/12285ddf5427d9f92603/US7046964.pdf
https://patentimages.storage.googleapis.com/pdfs/04e6685d2a4731c596de/US7190937.pdf

 

[gary123]

Interesting reading UPMan.

Without going into detail. this is my take on the feature.

Is it possible to modify or configure CC to work on DMR - yes
Is it practical to make these modifications - No
Would such modifications be reliable - No (will constantly false on impulse types of noise)

bottom line is Uniden is correct in not trying to support CC on DMR or TDMA types of signals

 

[N9JIG]

Interesting reading UPMan.
Without going into detail. this is my take on the feature.
Is it possible to modify or configure CC to work on DMR - yes
Is it practical to make these modifications - No
Would such modifications be reliable - No (will constantly false on impulse types of noise)
bottom line is Uniden is correct in not trying to support CC on DMR or TDMA types of signals

Not quite. CC works fine on DMR repeaters, it just the mobile or simplex TDMA transmissions it cannot detect.

I often get DMR/TDMA repeater hits just fine on my Uniden DMR scanners.

 

[gary123]

Good point N9JIG. I was assuming that the CC issue was in picking up simplex or single time slot users. The repeater sends both time slots even if only one is active. This is why the scanner can get a CC hit.

 

[Ubbe]

I can recommend Aceco SC1 plus for detecting digital transmissions like tetra and DMR mobiles. It also detects mobile phones and works excellent with all kinds of signals. The only negative is that it lacks a memory function.

/Ubbe

 

[gary123]

Im using a SDR stick and searching 1 and 2 meg segments at a time

 

[pb_lonny]

Here is an audio sample. Launceston Analytical Radio Scanning : Digital Audio on 493.225MHz

 

[pb_lonny]

Thanks for the information, makes sense now.

 

[racingfan360]

Here is an audio sample. Launceston Analytical Radio Scanning : Digital Audio on 493.225MHz

To confirm, that is a DMR Repeater signal, so I'd expect Close Call to pick up on it.

 

[gary123]

One nice future use for CC would be a dual sensitivity setting one for in city/town and the other for in the country. Monitoring via a SDR lets me see the relative signal strengths and when out of town I use a preamp to pick up repeaters (works/roards etc) for the various small towns in the ares. If CC was a bit more sensitive in these low noise environments it would add a lot to the scanners performance.

 

[ynot58]

Dmr nxdn

Trx1 on spectrum sweeper detects all inputs dmr and nxdn regardless of duty cycles on simplex trunked or conventional as it simply picks up the frequency during sweep. The dmr input for example may not trigger close call but spectrum sweeper stops on the input frequencies because the person is still keyed up talking after duty cycle And is monitoring it thus showing the frequency and relevant information and has never failed yet and works at a decent distance

 

[vizzini]

Trx1 on spectrum sweeper detects all inputs dmr and nxdn regardless of duty cycles on simplex trunked or conventional as it simply picks up the frequency during sweep. The dmr input for example may not trigger close call but spectrum sweeper stops on the input frequencies because the person is still keyed up talking after duty cycle And is monitoring it thus showing the frequency and relevant information and has never failed yet and works at a decent distance

Does SDS100 have the ability to do "sweeps"? I'm not sure if Analyze or Discovery does something like TRX-1's sweep. If so, then SDS should also be able to pick up input DMR transmissions.

 

[Ubbe]

Whistlers Spectrum Sweep are probably patented. Uniden can use its slow search function to achive the same thing but it could take ages to hit a frequency just when someone transmits on it.

/Ubbe

 

[AA6IO]

I have one of my Zumspots parked on 433.1000 Mhz for DMR on time slot 2. Have several static talk groups going through Brandmeister. My SDS-100 using close call picks up all these transmissions flawlessly, at least within the confines of my house and nearby outside. Audio quality of DMR on SDS-100 from Zumspot is excellent. Even shows the Talk Group and individual DMR (CCS7) IDs.

 

[Ubbe]

Your DMR hotspot transmits a carrier on both timeslots, a continous wave, but only sends information in the timeslot you have configured to use.

/Ubbe