domenica 1 luglio 2018

welle.io / DAB


Searching for a DAB/DAB+ decoder I found this useful software running on Windows 10, Linux, macOS, Android. The picture above show a DAB signal ( OFDM modulation: Orthogonal Frequency Division Multiplexing ) with a bandwidth of 1,536 MHz, 1536 carriers at 1 kHz spacing and a symbol rate of 800 Hz.

welle.io is an open source software with support for rtl-sdr (RTL2832U) and airspy. I tested the software with an AirSpy sdr receiver. After the program launch, welle.io detected automatically the sdr and start to scan the frequencies for any possibile DAB transmission.
The scanning frequency was very quickly and after few minutes I found 2 DAB carriers ( 30 stations ).



The second picture show the program window with many useful informations about the DAB signal: a stations list ( in this case 30 stations - channels 12A and 12C ), station name, signal strenght, error code, program type, Kbps, DAB audio mode, an image of the current audio program ( normally a cover of the on air song… ) and other technical informations:

- Sdr device
- Channel and frequency
- Frequency corrections
- SNR
- Frames error
- RS Error
- AAC error
- Frame Synchronization
- FIC CRC

The three rectangles are an indicator for the signal quality and decoding, from left to right:

1. Signal sysnchronization: red = out of sync / green: sync
2. FIC CRC Fast Information Channel Checksum: red = NO CRC / green = CRC OK
3. Frame errors: red = Error / green: No error

Another interesting feature is the "waveform visualizer" window useful to have an "eye quality" view of the signal.



More info here : https://www.welle.io/

Sources:
Please visit the GitHub repository: https://github.com/albrechtl/welle.io


giovedì 21 giugno 2018

VFT - T207 detector tool


This VFT signal was recorded in july 2016.


After some necessary "cuts" I isolated the FSk signal.




As showed on the pictures above I found the bits sequence on air...


Using the "T207-detector" coded by Antonio Anselmi and Christoph Mayer is was very simple to find out a T207 encoding in FSK bitstreams.

More info:
T207
GNU Octave, scientific programming language

73 de Ik1yde

mercoledì 20 dicembre 2017

HF Fax / JAPAN METEOROLOGICAL AGENCY-TOKYO, JMH

Japan Meteorological fax received via remote sdr ( KiwiSdr ).

Facsimile test chart

Facsimile test chart

500HPA HEIGHT, VORTICITY PROGNOSIS (24HOUR ) and SURFACE PRESSURE, PRECIPITATION PROGNOSIS 0440 AWJP 00 COASTAL WAVE ANALYSIS (24HOUR )

Meteorological satellite picture


850HPA HEIGHT, TEMPERATURE, DEW POINT 0320 ASAS 00 THE FIRST RETRANSMISSION OF 0240 DEPRESSION


More info about Japan Metereological Agency

mercoledì 6 dicembre 2017

M42


Russian diplomatic station heard some weeks ago on HF.


Fsk modulation with a symbol rate of 100 Bd and 500 Hz shift.


The bitstream after demod shows a typical 7-bit structure (5 bit + 1 bit START and 1 STOP bit).


By removing the start and end bits, we obtain sequences of 10 groups of 5 letters each as shown in the figure.


Fsk transmission followed by op chat in morse code.

venerdì 24 novembre 2017

Inmarsat D+ / Inmarsat's satellite paging system

Inmarsat D+ paging system received yesterday night on L-Band. This is a signal downlink from satellite.


The symbol rate is 4 symbols/sec and 5 bits / symbol ( 20 bps ).


Modulation is a 32-MFSK


"The main use of this technology nowadays is in tracking trucks and buoys and SCADA applications".





lunedì 20 novembre 2017

MIL188-110A transporting FED-1052 protocol


MIL188-110A waveform ( acf 200ms ) sending encrypted email data.


Output bitstream.


FED-1052 protocol.


CFB encryption.



Source about CFB

mercoledì 8 novembre 2017

802.15.4 IoT - Internet of Things...


"IEEE 802.15.4 is a technical standard which defines the operation of low-rate wireless personal area networks (LR-WPANs)". This signal and many other signal like this are easily recevible in our house with a simple antenna. Probably this is a ZigBee device working on 868 MHz ( european standard frequency ).


Modulation and symbol rate.


Burst sequence.


Packet frame: 199 bits: "32 bits synchronization + 8 bits packet delimiter + 7 bits PSDU lenght + 1 bit reserved service" followed by PSDU ( variable lenght from 0 to 127 bytes )


in the next post a more in-depth analysis.