How to get the message out, when “someone” shuts down the internet

Pavel Táborský

Credentials

• ~10+ years in IT, GSM networks before that

• HAM License ~1 year

• And that’s about it…

Credits...

• Bruce Sutherland, KO4IN

• How To Get Your Message Out When Your Government Turns Off The Internet

– @DEFCON19

HAM Radio

• Old tech since about 1900

• Usually two skilled operators needed, one at each end

• Ionospheric conditions…

• (Moon, Aircraft, Satellites)

Gear

• Wet dream HF/SSB station

– HF radio 40k+

– Mast + yagi dir antenna array ~100k

– Power amplifier(s) etc.

• Or on Budget:

– Yaesu FT-897 ~20k

– Longwire antena ~the cost of the wire

– Essentially what WW2 operators did

We will use

• HAM radio license…

• APRS capable handheld radio ~5k

• Yagi antenna made of tape measure and PVC pipe ~200

• VHF Band (145.825/144.800)

• HAM radio satellite (OSCAR)

– ISS

– PC-SAT (Navy OSCAR – 44)

• Twitter

We will use

Alternatively going cheap(er)

APRS

• Developed in mid ‘80s by Bob Bruninga(WB4APR)

• Originally position reporting system

• Then Messages and WX reports

• X.25 for HAMs

– 1200baud

– AFSK modulation

• APRS is a retronym of WB4APR

– Automatic Packet/Position Reporting System

APRS cont’d

• The network consists of radio stations operating entirely with broadcasted packets

• Digipeaters retransmit packets with store and forward approach and follow DIGIPATH

• Packets are picked up by internet gateways (iGate) and handed over to the the APRS-IS to plot on a map

• Allows for sending variety of packet types (position, object, telemetry, weather etc.)

APRS cont’d

Infrastructure needed

• APRS iGate (preferably in another country)

• APRS Digipeater (orbiting)

• APRS -> Twitter gateway

• Twitter

ISS Footprint

APRS via Satellite

• Set radio transmit to 145.825

• ARISS on the 1st position in the digipath

• Compose an APRS message to TWITR

• Wait for the satellite to be over the horizon

– And chosen iGate in the footprint

• Send the message

• Message gets digipeated back to ground iGate

• And picked by the APRS-IS network

• Subsequently by the APRS -> twitter gateway

APRS -> twitter gateway

• Runs under hamradiotweets.com atm

• Interfaces to the aprs.fi (APRS-IS) API to pull the messages

• Tweets…

OSCAR

• Stands for Orbital Satellite Carrying Amateur Radio

• ISS

• PC-SAT (Navy OSCAR-44)

• OSCAR status:

– http://oscar.dcarr.org/

Satellite pass prediction

• Web Based

– http://www.heavens-above.com/

– http://www.n2yo.com/

• Offline

– Satscape

Not foolproof

• The system can be jammed

• You can be triangulated

• Twitter fail whale