Tetra decoding
- Thread starter sq5bpf
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what do you mean by "TETRA audio files"?
if you mean the tetra audio files recorded by telive (from /tetra/out), then these are normal ogg files, any player which supports ogg will play it
if you mean acelp files (like the ones from /tetra/in), then /tetra/bin/tplay < file.acelp will play it
if you mean baseband recordings, then you would have to modify one of the gnuradio flowgraphs to use a file source to play this file (instead of the sdr source), and do some decimation/resampling/whatever
ET-NL
Member
Good afternoon,
I have some quiestions.
The (commercial) network I'm listening to has several site's (I can hear 8 site's / frequencies of this network from my location). One of the channels has something strange, I tune in to a frequency and the downlink in Telive gives a value of 2MHz lower than what GNURadio is tuned to. All other frequencies are (almost) the same in GNURadio and Telive.
The value Telive is telling me is comming out of the data, can it be that someone made a mistake putting the downlink freq in to the site or doesn't this work this way ?
Second question what does the LA value in telive tells me ?
Elmar
I have some quiestions.
The (commercial) network I'm listening to has several site's (I can hear 8 site's / frequencies of this network from my location). One of the channels has something strange, I tune in to a frequency and the downlink in Telive gives a value of 2MHz lower than what GNURadio is tuned to. All other frequencies are (almost) the same in GNURadio and Telive.
The value Telive is telling me is comming out of the data, can it be that someone made a mistake putting the downlink freq in to the site or doesn't this work this way ?
Second question what does the LA value in telive tells me ?
Elmar
high capacity cell
For the 2 MHz under or over , it's maybe a double capacity cell . Here I have the main frequency on 426,900 Mhz and another on 427,2 MHz .Telive is displaying 426,900 when I m on 427,2 MHZ . That means that that this cell has 8 possibles channels .
For the 2 MHz under or over , it's maybe a double capacity cell . Here I have the main frequency on 426,900 Mhz and another on 427,2 MHz .Telive is displaying 426,900 when I m on 427,2 MHZ . That means that that this cell has 8 possibles channels .
ET-NL
Member
If that's the case, should there be a signal with the same CC on the frequncy that Telive tells me?
Elmar
all parameters should be the same on both frequencies: ul/dl frequencies, CC, LA, MCC/MNC/etc...
Yes it should be.
Telive only reports the frequency of the "control"-frequency of each site, so having several frequencies with the same information is normal.
I've mainly seen sites with 1, 2 and 4 frequencies (giving capacity of 3, 7 or 15 simultanious calls. 4 timeslots per frequency, and at least one on the system channel reserved for system signalling).
However it's not always easy to determine how big a site is with the current Telive version. Some systems only have the "control"-frequency active until the traffic increases. By this it can look like a site only have one frequency, but additional channels might pop-up when needed. Hopefully later versions can contain more information about the available channels on the active site, but also neighbour information (all this is sent but currently not parsed by the application). This would simplify a lot when trying to map how a system is setup.
There are also other cases when a frequency is a non-intelligent relay to a site. I've only seen one such case, but then the relaying frequency had the same CC, LA and frequency information as the main site. I guess there must be some more information in the system data telling the Tetra radios to not revert to the system frequency.
I've tried to decode IQ-files recorded with SDR-sharp by modifying the gnuradio flowgraphs. I could read the file but I never succeeded to make gnuradio read the file correctly.
Being able to do this would be quite interesting if having old IQ-files containing Tetra signals saved (like I have).
When reading about this it though seems like Gnuradio 3.7 is better on decoding IQ-files, so I'll maybe play more with this sometime if I update Gnuradio. If successfull I'll explain how to do.
Hello,
I´m happy with telive, thanks to sq5bpf !!!
Now i´m monitoring two networks in my city.
One of this is very easy and the program decode very well, but another even with a great signal (ext antenna), the program have very problems to decode and present (many times) te phrase (decode partialy)
"could not find succesive burst training sequence"
The only diferent that i can see is:
Advanced Link: 0 (Network that can decode)
Advanced Link: 1 (Network who decode partialy)
I think i was doing something bad
Very thanks for you
P.D. Also tell me
too much changes, are you monitoring only one cell?
I´m happy with telive, thanks to sq5bpf !!!
Now i´m monitoring two networks in my city.
One of this is very easy and the program decode very well, but another even with a great signal (ext antenna), the program have very problems to decode and present (many times) te phrase (decode partialy)
"could not find succesive burst training sequence"
The only diferent that i can see is:
Advanced Link: 0 (Network that can decode)
Advanced Link: 1 (Network who decode partialy)
I think i was doing something bad
Very thanks for you
P.D. Also tell me
too much changes, are you monitoring only one cell?
Last edited:
this is usually caused by low signal level, incorrect tuning (check ppm and frequency), or interference. Advanced Link: 1 has nothing to do with it.
the signal doesn't decode correctly, and you're getting strange network parameters in the incorrect decodes. the software reports this error when these parameters change too often. this error is implemented, because some people monitored multiple cells with one telive instance, and telive would display incorrect information or give garbled recordings (when two calls happened on the same usage index)
Ok
many thanks for your answer, is possible a interference, i run 25 km with my car in all directions, but not can decode this frecuency.
I still searching another frecuency for the same network. it can resolve my problem.
Thank you a lot.
many thanks for your answer, is possible a interference, i run 25 km with my car in all directions, but not can decode this frecuency.
I still searching another frecuency for the same network. it can resolve my problem.
Thank you a lot.
ET-NL
Member
Thanks, found the second freq for some of the cell's. (not all cells'seem to have a second channel)
One of the cell's was strange same up / down freq, same MCC/MNC but diferent CC.
Elmar
If you tested so much without success, it definatelly sounds like some interference.
I actually have a similar case which dissapeared when I changed the frequency-offset in gnuradio, ie;
427,475M + 500k = 427,975 MHz (didn't decode)
427,575M + 400k = 427,975 MHz (decodes without problem)
In a big system (62 sites) that I monitor I've several cases like this.With so many channels it's natural that they reuse some frequencies, and in some cases some sites have some frequencies overlapping, but not all. In such case this can happen, but that also means that one site is weaker and you only hear the strong site on the overlapping channels.
This is the reason why the CC is used, to make the radio separate the different sites in case the radio would hear another site on the same frequencies.
ET-NL
Member
Thanks this is als also a large network, I Will have a look At the signal strength of both freq.
Elmar
Elmar
and this is one of the reasons why the offset is configurable
rtl-sdr sticks are not great receivers (in absolute terms, they are great for the price that you pay for them):
- they can have mirror images too, only the IF frequency is not exposed by the driver, but is usually around a few MHz with R820T (but usually 0 in case of E4000). the sdr further complicates the analysis of this
- they overload easily because of the 8-bit adc in the RTL2832
- they have almost no frontend filtering
- believe it or not, they were designed to watch tv from multi-kW stations with good antennas, and not listen to tetra
actually it's a miracle that they work so well with all these shortcomings (and for such a low price)
ET-NL
Member
At the moment I'm filling my ssi_descriptions file with names.
But Telive is aligning the names to the right. Is there a way to align the names to the left (now I'm aligning the names with spaces)
But Telive is aligning the names to the right. Is there a way to align the names to the left (now I'm aligning the names with spaces)
RMW1010
Member
Did anyone try to adapt the GNURADIO flowgraph to work with a Funcube?
I want to monitor a specific network, but the RTL dongle is a bit to un-sensitive.
Thanks!
I want to monitor a specific network, but the RTL dongle is a bit to un-sensitive.
Thanks!
oz1jua
Member
Funcube Dongle
In stead I have an HackRf and this is much better for un-sensitive networks.
Remeber that not all Funcube Dongle can tune in to Tetra frq. Only version 1 can be tuned.
Yes I have Telive op and running after hard reading Thanks to sq5bpf !
I have try to use the Funcube Dongle. But it gave me to much trouble using this with GNU Radio.I have a very powerfull base station near my QTH about 100 meter and and this is giving to much overload to the Funcube, so i can not recommand this wiith Telive.
In stead I have an HackRf and this is much better for un-sensitive networks.
Remeber that not all Funcube Dongle can tune in to Tetra frq. Only version 1 can be tuned.
Yes I have Telive op and running after hard reading Thanks to sq5bpf !
oz1jua
Member
Can any one explain where the GSSI is ?
I can se a lot of ISSI called SSI. But haw is this compared to GSSI. Or is SSI some part of GSSI.
I can se a lot of ISSI called SSI. But haw is this compared to GSSI. Or is SSI some part of GSSI.
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