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(a)lists.osmocom.org
To: "Felix Rublack" frubi(a)frubi.net, tetra(a)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(a)frubi.net>
Hi Ari,
On 17.12.2012 10:37, Ari Kaspari wrote:
> In your Picture
>
http://tetra.osmocom.org/trac/graphviz/caf863214dab2ac9e1beead8b122318020ec…
> 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