TRX-1: Special project: DMR talkaround.

[chris451rr]

I have the TRX-1 whistler scanner. I also have DMR Tier1 radios and a DMR Tier 2 radio.
The TRX-1 will decode the tier1 radio direct or through a repeater. It will decode a DMR tier 2 radio through a repeater but not direct. However I note the TDMA format of the tier 2 radio, and found that a tier 1 will not decode it (except through a repeater) and if the TRX-1 is tuned to the uplink and set to DMR it will not decode that, although the Smeter bobs up and down it won't display a talk group.
So evidently Tier 2 uplink is a different format than a tier 2 downlink (the downlink has both uplinks on it and continous carrier and the uplink alternates between 2 uplinks who take their turns.
Project: Tune to DMR inputs to repeaters and see if you can find one that you can decode or see an RID for.
In P25 the radio has no problem decoding an input or an output for non TDMA uplinks (we don't have a phase 3 around here but some drift in during summer openings)

It's been really difficult to catch a dmr uplink thats close enough to hear, even if I know when they are talking and hear them on the downlink. I have succeeded with uplinks on P25. They carry at least a mile from a car.

 

[racingfan360]

....and a DMR Tier 2 radio.

Which type?

My TRX-1 has no issues decoding any Tier II DMR radio, whether operating in Direct or Repeater mode (decoding both uplink and downlink transmissions).

 

[mike_s104]

Are you trying to hear a radio that you own?

Sent from my SM-G930V using Tapatalk

 

[chris451rr]

I am trying to decode a Radioddity GD77 uplink and it works through the repeater and decodes, but it won't decode direct talkaround or on the input. The DM-5r will not decode it direct only through a repeater. However a baofeng DM-5R (not really tdma compatable but it will talk to the repeater) it decodes OK. I have not tried a TYT 380 yet but someone here has one when I get to try it.

 

[racingfan360]

A DMR transceiver will never decode another transceiver's uplink signal to a repeater when operating in Tier II or Tier III. Correctly programmed it will only decode simplex or repeater output.

Tier I is simplex only.

I have no idea if a TRX1 decodes Tier I: I think you're suggesting it does?

 

[chris451rr]

Just to confirm, you have decoded the TDMA side (the carrier is pulsing at about 45% duty cycle?
In my case I went to tune mode (the radio automatically tries to figure out what it is hearing and decode whatever format is there)
With the GD77 transmitting I see the s meter bounce but no decode. Just can't seem to pick that up. Does fine on Tier 1 (continuous carrier). Yet to confirm I decode any DMR inputs yet.

 

[dcr_inc]

Radio to radio, IE: Talkaround mode requires one of the radios to act as a master to supply the timing for the other radios..Its called DMO mode..

 

[chris451rr]

Yep I have a tier 1 radio and it decodes that same as a repeater output. But these are chinese radios so who knows what chipset is in these I have not torn into it yet. However it does not decode a tier 2 radio that transmits tdma all the time. But the repeater does and it decodes the repeater output.

 

[chris451rr]

So the first radio that transmits becomes the master?

 

[chris451rr]

So if there is just one radio not two and you transmit with one radio, then its trying to send a sync and will not leave that mode until it gets a timing response?

 

[racingfan360]

Just to confirm, you have decoded the TDMA side (the carrier is pulsing at about 45% duty cycle?
In my case I went to tune mode (the radio automatically tries to figure out what it is hearing and decode whatever format is there)
With the GD77 transmitting I see the s meter bounce but no decode. Just can't seem to pick that up. Does fine on Tier 1 (continuous carrier). Yet to confirm I decode any DMR inputs yet.

All DMR is TDMA, not just the Uplink/Mobile side. But to confirm, I can happily decode a range of DMR Tier II signals...including those in Simplex mode and the mobile/uplink side of a repeater set up. Have you tried programming the channel as DMR into memory on the TRX1?