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/caf863214dab2ac9e1beead8b122318020ecb403.dot.png
> 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