Hello,
i found your brilliant project yesterday and asked me, if it is possible to use a signal from a radioscanner discriminator output for your omso-tetra tool.
In your Picture http://tetra.osmocom.org/trac/graphviz/caf863214dab2ac9e1beead8b122318020ecb... it seems to me, that I only need PCM Samples from my radioscanner. Thus I think i can stream the discriminator output via soundcard (PCM-Samples) into a linux pipe and use this pipe for your omso-tetra tool.
Is this possible? Or is my radioscanner not possible to "stream" the correct channel pattern?
Best Regards Ari Kaspari
Hi Ari,
On 17.12.2012 10:37, Ari Kaspari wrote:
In your Picture http://tetra.osmocom.org/trac/graphviz/caf863214dab2ac9e1beead8b122318020ecb... it seems to me, that I only need PCM Samples from my radioscanner. Thus I think i can stream the discriminator output via soundcard (PCM-Samples) into a linux pipe and use this pipe for your omso-tetra tool.
Is this possible? Or is my radioscanner not possible to "stream" the correct channel pattern?
No, i don't think so. Your radio scanner does FM demodulation. But the TETRA signal is modulated with Pi/4-DQPSK (or QAM - not supported by osmocom-tetra). So the real information is already lost, when it comes out of the discriminator output.
The FUNcube Dongle (linked schematics) does no demodulation. It just digitise the I/Q-Data and puts it in the left/right channel of the PCM stream.
Greetings Felix
Hi thank you for your comment.
What do you think about the following thought:
I take two old radioscanners each has 12.5 kHz channel pattern ("Kanalraster") , Tetra uses 25 kHz. Then I make for each scanner a FM modulation in Software or on FPGA and after a signal addition. Now i should have the modulated Pi/4-DQPSK signal back. Or haven’t I?
2012/12/17 Felix Rublack frubi@frubi.net
Hi Ari,
On 17.12.2012 10:37, Ari Kaspari wrote:
In your Picture
http://tetra.osmocom.org/trac/graphviz/caf863214dab2ac9e1beead8b122318020ecb...
it seems to me, that I only need PCM Samples from my radioscanner. Thus I think i can stream the discriminator output via soundcard (PCM-Samples) into a linux pipe and use this pipe for your omso-tetra
tool.
Is this possible? Or is my radioscanner not possible to "stream" the correct channel
pattern?
No, i don't think so. Your radio scanner does FM demodulation. But the TETRA signal is modulated with Pi/4-DQPSK (or QAM - not supported by osmocom-tetra). So the real information is already lost, when it comes out of the discriminator output.
The FUNcube Dongle (linked schematics) does no demodulation. It just digitise the I/Q-Data and puts it in the left/right channel of the PCM stream.
Greetings Felix
OR you get a €20 (even less) RTL usb sdr dongle and save a lot of time and effort... http://sdr.osmocom.org/trac/wiki/rtl-sdr8-)= From: tetra-bounces@lists.osmocom.org To: "Felix Rublack" frubi@frubi.net, tetra@lists.osmocom.org Cc: Date: Mon, 17 Dec 2012 15:09:40 +0100 Subject: Re: Osmocom TETRA software
Hi thank you for your comment.> What do you think about the following thought:> I take two old radioscanners each has 12.5 kHz channel pattern ("Kanalraster") , Tetra uses 25 kHz.> Then I make for each scanner a FM modulation in Software or on FPGA and after a signal addition. Now i should have the modulated Pi/4-DQPSK signal back. Or haven’t I?
2012/12/17 Felix Rublack frubi@frubi.net>
Hi Ari,
On 17.12.2012 10:37, Ari Kaspari wrote:>
In your Picture> http://tetra.osmocom.org/trac/graphviz/caf863214dab2ac9e1beead8b122318020ecb... it seems to me, that I only need PCM Samples from my radioscanner.> Thus I think i can stream the discriminator output via soundcard> (PCM-Samples) into a linux pipe and use this pipe for your omso-tetra tool.>
Is this possible?> Or is my radioscanner not possible to "stream" the correct channel pattern?
No, i don't think so. Your radio scanner does FM demodulation. But the>
TETRA signal is modulated with Pi/4-DQPSK (or QAM - not supported by> osmocom-tetra). So the real information is already lost, when it comes> out of the discriminator output.
The FUNcube Dongle (linked schematics) does no demodulation. It just> digitise the I/Q-Data and puts it in the left/right channel of the PCM> stream.
Greetings
Felix
-
Ari Kaspari -
Felix Rublack -
sinager＠tarapippo.net