TRX-1: DMR & DMRs

eyes00only

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While doing a limit search today I noticed two different displays (DMR & DMRs).
What is the difference?
 

K2AJB

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DMR is an FDMA transmission, which usually is a repeater output.

DMRs is a TDMA DMR transmission, which always is either the input to a repeater or a simplex frequency.
 

eyes00only

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Thanks. I'm not sure how DMR & NXDN work as this is my first scanner that receives them. Unfortunately they're about the only thing the TRX1
is good for in my area. P25 Phase I, Phase II. and Simulcast suck with the scanner.
 

JJMNIZ

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Thanks. I'm not sure how DMR & NXDN work as this is my first scanner that receives them. Unfortunately they're about the only thing the TRX1
is good for in my area. P25 Phase I, Phase II. and Simulcast suck with the scanner.
eyes00only,m

When "DMRs" is displayed, do you hear the users talking?

Also, are you sure they are talking directly to each other with no repeater involved?



Thanks
 

eyes00only

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I just searched for a short time while waiting for someone in downtown Denver. I do think I heard audio when DMRs was displayed.
I was probably very close so it probably was a repeater input or simplex.
 

JJMNIZ

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I just searched for a short time while waiting for someone in downtown Denver. I do think I heard audio when DMRs was displayed.
I was probably very close so it probably was a repeater input or simplex.
I now have a brand new TRX-1. It reliably decodes DMR traffic on several repeaters and produces very good quality audio. I can also pick up nearby units on their repeater input frequencies and the TRX-1 displays "DMRs".

However, nearby units talking directly to each other, without a repeater, are not decoded. I can hear their TDMA bursts with the TRX-1, but there is no recovered audio.I had hoped a new TRX-1 would resolve this situation.
 

KE5MC

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I'm not familiar with TRX-1 or how you have it setup. Simplex is usually done on TG 99, CC 1 and TS 1. Promiscuous/Monitor/Search mode depending on device and what manufacture calls it, is not as structured with program requirements as you are looking for information on the frequency, but don't know the details. On the other hand as I recall repeater operation establishes timing requirements that simplex HT to HT might not care about, however the TRX-1 might. I've seen a few threads on here discussing timing repeater vs. HT.
 

Ubbe

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I think I've seen it mentioned that if the simplex traffic where using slot 2 it could be a problem using Whistler scanners. But then I've seen postings about the mobiles not transmitting any slot numbers. But Uniden have said that their simplex decoding will not be 100% due to technical difficulties, and if that's the case then Whistler probably have the same issues.

I can do a test using different slots and see how well Uniden and Whistler can decode a simplex transmission.

/Ubbe
 

Ubbe

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It seems that the info about not using slot numbering in simplex are correct. The TRX-2 indicate slot 1 whatever slot I use in simplex and it decodes simplex perfectly every time with a DMRs indicator and displays all the traffic info. It does this with both DMR ticked or unticked as a valid mode in tune mode so it will automaticly switch to DMR from analog and I cannot monitor in analog mode. So there's another bug in the Whistler firmware.

The Uniden BCD536 doesn't decode the simplex signal at all and treats it as an analog signal. I have decoded DMR uplink to a repeater succesfully so it will anyhow work in that mode.

/Ubbe
 

JJMNIZ

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It seems that the info about not using slot numbering in simplex are correct. The TRX-2 indicate slot 1 whatever slot I use in simplex and it decodes simplex perfectly every time with a DMRs indicator and displays all the traffic info. It does this with both DMR ticked or unticked as a valid mode in tune mode so it will automaticly switch to DMR from analog and I cannot monitor in analog mode. So there's another bug in the Whistler firmware.

The Uniden BCD536 doesn't decode the simplex signal at all and treats it as an analog signal. I have decoded DMR uplink to a repeater succesfully so it will anyhow work in that mode.

/Ubbe
Your TRX-2 decodes simplex perfectly in the Tune mode? FYI, my TRX-1 decodes nothing.

I wonder if a firmware update could fix this, and if Whistler has any plans for it.

Thanks for your help Ubbe
 

JJMNIZ

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Your TRX-2 decodes simplex perfectly in the Tune mode? FYI, my TRX-1 decodes nothing.

I wonder if a firmware update could fix this, and if Whistler has any plans for it.

Thanks for your help Ubbe
Also FYI:
The facility I wish to monitor has two groups, one on Color Code 1 with the other on Color code 2. They have a mix of Vertex Standard radios and Motorola radios that operate in the TDMA mode without a repeater.
 

Ubbe

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As simplex works for others using TRX-1, check if you are running the latest firmware.
I'm running the TRX-2e firmware and if I program a channel and let it receive DMR simplex that also works but it doesn't indicate DMRs.
So there's some bugs here and there in the TRX-2e firmware and will let Whistler know about them.

/Ubbe
 
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JJMNIZ

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My TRX-1 has the following:

PC Application 3.34 Bld 669
CPU Firmware 5.8
DSP Firmware 3.2

All are shown as "Current".


As explained before, my brand new TRX-1 is able to properly decode audio and also display Color Code and Time Slot info when receiving a transmission from a nearby mobile on a repeater input frequency. Also, DMRs is displayed during the transmission.

However, my brand new TRX-1 does not decode anything nor display anything when a nearby radio is transmitting on a simplex channel (direct radio to radio, no repeater used). The staccato TDMA signal can be heard if the scanner is in the analog mode. This is on a UHF business channel 466.2875 MHz.

Hopefully this will be resolved by Whistler.
 

KE5MC

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What's the distance from your new TRX-1 and the "nearby" simplex transmitting radio? It could be a case of overloading the TRX-1 front end.
 

JJMNIZ

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What's the distance from your new TRX-1 and the "nearby" simplex transmitting radio? It could be a case of overloading the TRX-1 front end.
The simplex portables can be 20 feet away or in a building 2,000 feet away and the TRX-1, when in the analog mode, hears the staccato TDMA transmissions from the simplex portables. This indicates that there is no overload or interference.
 

Ubbe

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The staccato TDMA signal can be heard if the scanner is in the analog mode.
Do you need to open the squelch, set it to zero, to be able to hear the audio?
My TRX-2 doesn't open squelch from simplex or uplink transmissions and needs to be monitored with the squelch open. Also another person using a TRX-1 could not hear the one slot transmissions as well if the squelch where set at its normal position.

If you can hear the staccato using a normal squelch setting then it's either something wrong with the scanner or the transmissions are not DMR simplex. As you can decode uplink, which only differ in some databytes and the timing of the slots and everything are the same, the scanner should at least mute the analog audio and try to decode the datastream.

Vertex was bought by Motorola so I don't know if they might be using some sort of special common DMR simplex mode at that facility. In that case you could record an IF sample using SDR# and a SDR dongle so that it can be played back and analyzed. Whistler would otherwise have no clue of how to add that mode to their firmware.

/Ubbe
 

jhampton2000

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For reference my TRX-1 is able to decode Motorola, Vertex and Hytera DMR simplex/uplink channels ok.

It's running:
PC Application 3.34 Bld 669
CPU Firmware 5.8
DSP Firmware 3.2

I usually program in the frequency as a memory channel and select DMR as the modulation type: I don't rely on Auto decode. Also the channels are in the clear and not encrypted (although even with encryption they decode ok when the TRX is set to 'digital noise' or 'audio tone').

>But Uniden have said that their simplex decoding will not be 100% due to technical difficulties, and if that's the case then Whistler probably have >the same issues.
While the latter run of firmware updates to the Uniden made a significant improvement to DMR simplex decoding I have always found the TRX1 to be in the 90-100% decode region. I still think this is a result of the Uniden being more selective but less sensitive, the TRX more sensitive but less selective (comparative tests with discriminator tapped analogue scanners and DSD+ exhibit similar results).
 

Ubbe

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TRX can currently only do auto decode between analog and P25. The later added DMR and NXDN modes cannot do auto from analog. Hopefully it will change in next firmware release as the service search in the EU firmware can autoswitch between DMR and analog, the same way that simplex DMR and analog now do in tune mode, whether you want it or not.

If I monitor the same repeater systems using DMR radio and Uniden and TRX-2 I've always had a 100% DMR decode with the TRX-2.
Uniden have always struggled with DMR decode quality. But TRX-2 have a worse RF quality, it is not as sensitive as Uniden and especially at VHF it is extremly interference prone while at the same time not have as good sensitivity as Uniden. The TRX squelch design also stops it from being set sensitive enough.

/Ubbe
 

n4jri

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I'm not noticing a DMRs on my display, but will watch closer. Am noticing several users using simplex in the mode where the radio does catch a signal and records, but appears to be silent. If I listen on headphones or playback at high volume, I hear the parade of pulses. Sketchiest reception is with a small company using the freq for switching railcars. It's tough listening in a high RF environment, and even popping the freq into 'Tune' mode sometimes doesn't do the trick. Better performance programming it as a memory channel in DMR mode.

Have recently experimented with a large local theatre where I sometimes perform. Audio from the transmissions is varied in quality, but sometimes more clear a few blocks away than within a block. All transmissions show as timeslot 1, but each frequency has a unique color code and talkgroup ID. No indication of more than one talkgroup per frequency, so I'll also assume that only one timeslot is used. At a recent performance, I set all licensed freqs to DMR and let the radios record from inside the building. Reception was generally good using no attenuation. Found no new freqs or TGs active that I hadn't already discovered from the outside.

The biggest problem with simplex for me is that audio sounds muddier. This is true both in the quiet building and in the noisy railyard. Both users have two factors in common. First, they're all using body-mounted radios with external speaker mics. Theatre people have radios on the hip, rail guys have them on the chest. Second, both are in a downtown RF environment. Could also be that users are talking too far away, or off-angle from their mics.

73/Allen (N4JRI)
 

Ubbe

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Digital systems are much more critical of the exact right level of audio from the microphone. Speaking too low and the system only use a couple of bits of resolution at the bottom of the available dynamics. Speaking too loud and only a couple of the top bits are used.

If only a couple of the bits of the possible dynamics are used it will sound almost like a square wave when you demodulate a voice audio, very muddy and no treble. It doesn't help if the radios have been programmed with noise reduction as those algoritms are far from perfect and manhandles any voice audio and makes it harder to understand.

Analog systems are much more forgiving to unmatched mic levels.

/Ubbe
 
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