Is it possible to decode TETRA voice with a discriminator tap?

[zerosix]

I am aware I can use an SDR with SDRSharp for tetra demodulation, but I am wondering if it technically possible to decode the voice protocol with a Discriminator tap.

I know most programs like DSD+ do not offer support for the TETRA protocol, but I was hoping there might be a workaround. thanks in advance

 

[LimaZulu]

The main issue here is that probably 99% of the scanners does not have the ability provide the appropriate bandwidth. Maybe some more modern one could do that. About the software - if you satisfy the above, maybe you should be able to achieve something with GNU Radio

 

[oz1jua]

Dsdauthor has explain this:

It is not likely that TETRA could be supported. Even with sufficient bandwidth and sound card sample rates the pi/4 DQPSK modulation is not compatible with an FM discriminator.

 

[ludek-brno]

DSD + FL has practically exhausted it from new radio systems and defacto has nothing more to offer. !!!

Is voice DPMR still a challenge?

 

[slicerwizard]

DSD+ FL decodes dPMR voice, at least AMBE voice...


DSD+ 2.268

Added dPMR link control display and AMBE+2 voice synthesis. dPMR decoding has to be enabled.

 

[merlin]

I have yet to see a digital radio (scanner or other) that has the typical 'discriminator'
All the decoding is done in the DSP.
I suppose with a firmware mod, the raw audio could be ported to say external audio.
That piped into newer DSD+ it should at least decode dPMR and AMBE+2

 

[racingfan360]

I have yet to see a digital radio (scanner or other) that has the typical 'discriminator'

The Whistler TRX1 and TRX2 both have built in discriminatory taps. Believe the AOR DV1 has one as well.

 

[Ubbe]

The TRX-2 "discriminator" tap works with all digital modes I have tried except Tetra that can't use a FM demodulated signal.

/Ubbe

 

[merlin]

The TRX-2 "discriminator" tap works with all digital modes I have tried except Tetra that can't use a FM demodulated signal.

/Ubbe

These have the RF front end and digital backend and that coincides with what I said about the DSP.
A tap at the DAC would be the same as 'discriminator' so the terminology is just keeping pace with modern digital radio.
Old school discriminators only demodulate true FM analog only. Nothing in those can separate the 4 discrete phases needed for digital. AFSK or FSK is the best they can do.
Hey, that TRX-2 is a nice design for digital. Decoding TETRA would take a dual core ARM processor to parse the very different code blocks.
oz1jua said it quite well.