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Funcube Dongle

The Funcube Dongle Pro (FCDP) is a small USB-key-sized low-bandwidth SDR.

It uses an audio codec as ADC (like many amateur radio projects) and thus can only be used for narrow-band signals up to 80kHz.

However, for capturing a single TETRA channel, those 80kHz is actually more than sufficient.

It is generally available for purchase from http://www.funcubedongle.com/ - however, it is out of stock almost all the time
and you will have to click the order button at exactly the right time in order to get one. Apparently it is impossible for
the manufacturer to keep up with the demand.

Hardware

Major components

The FCDP hardware seems to be using the following components:

Architecture

The hardware architecture therefore is quite simple:

The PIC24F implements the USB protocol/interfaces for HID (tuning) and audio towards the PC. It also drives the TI codec and the Elonics silicon tuner via an I2C interface.

Analog RF data enters the Elonics silicon tuner, where it undergoes zero-if down-conversion to complex I/Q baseband, which enters the TI audio codec where it is digitized using left/right channels for i/q. The resulting digital audio stream is passed to the PIC24F, which forwards it via USB to the host PC.

Image

Software

The OsmocomTETRA repository contains a demodulator script called fcdp-tetra_demod.py that can be used with the FCDP.
You have to use the 'qthid' application provided with the FCDP in order to tune to the respective tetra carrier frequency.

fcdp_pcb.jpg (206 KB) laforge, 05/30/2011 03:16 PM