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-sdr

8-)=

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/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