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".

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.

martedì 7 novembre 2017

Nokia Adaptive Message Terminal

Another interesting signal heard some days ago.

Looks like an FSK modulation....

Symbol rate: 301 Bd

Shift ~ 755 Hz Yes ! it's a Fsk modulation...

Bitstream after demod.

Bandwidth: ~950 Hz

...yes, it's a Nokia Adaptive Message Terminal...

More technical info:

- Antonio Anselmi's blog
- radioscanner

S4538, FLSU Asynch Request

Short burst, a BW5 waveform ( STANAG 4538 ).

FLSU Asynch Request.

Short encrypted data

A short FSK transmission transporting encrypted data.

Looking the bitstream is visible a KG84 encryption.