Main: Ham

See ReportBeaconsAndPassInfo for reporting info to us

Spacelink Format

AAUSAT4 transmits CSP packets encapsulated in a custom spacelink framing format. The radio subsystem works as a router, where subsystems communicate directly with the ground station server.

The spacelink frames start with a variable length training sequence (default 60 bytes 010101010....), followed by a 6 byte syncword ("OZ4CUB"). The packet format supports two different packet lengths, either 25 or 86 bytes. A one byte Frame Size Marker (FSM) is used to differentiate between long and short packets. The FSM is 0xA6 for short frames and 0x59 for long frames.

Next, 31 or 92 bytes (short or long packets) of FEC coded data follows. After applying the FEC, the FEC data length is:

Short Frame: ((2 + 4 + 23 + 2) bytes [data] + 32 bytes [RS] + 1 byte [Conv. tail]) * 2 [Conv.] = 128 bytes
Long Frame: ((2 + 4 + 84 + 2) bytes [data] + 32 bytes [RS] + 1 byte [Conv. tail] * 2 [Conv.] = 250 bytes

Technical Details

Example Python code for decoding the FEC is available as part of the BlueBox project:

obsolete - new version on way

Beacon details

AAUSAT4 has a CW beacon (30 wpm PARIS) and CSP encoded beacons in the ratio 1:10, meaning - 9 CSP encoded beacons - 1 CW beacon

The beacon transmission will start approximately 90 minutes after launch, and then transmit either FSK or CW encoded beacon every 30 seconds.

CW Beacon

CW beacon is constructed as follows

OZ4CUB Bx.x(battery voltage) Txx(temp)

An example from 24. May 2013 from AAUSAT3:

A CW beacon from 24. May 2013 Morse Alphabet is here

Handheld yagi

If you want to receive morse(cw) beacon a handheld antenna should be enough.

Yagi antenna


:-) AAUSAT4 emit two types of messages

1) Messages for which you need special decoding SW (and HW)

2) Old fashion morse/CW beacons.

It is 2) you can receive if you have an radio that can recieve around 437.425 MHz.

So you can record the morse/CW beacon from the audio/headphone output on the radio.

We use audacity (program) for editing sound and the beacon you see on the hoempage is just a screen snapshot from audacity. So I think hand decoding is possible :-) You can download orbitron(windows) or gpredict(linux) and select AAUSAT4 in cubesats. It can predict/calculate when you will be able to see AAUSAT4 meaning direction(azimuth) and elevation. So having a watch, a compass and a handheld antenna you should be able to point at AAUSAT4 and receive beacon.


Due to the 7.5km/Sec velocity there is doopler shift on the radio. AAUSAT3 is on 437.425 MHz but when comming over the horizon you should increase freq on radio with approx 12 kHz. 0KHz when above your head and subtract 12 kHz just before leaving behind the horizon. It is not so critical but many radios has a input filter with width approx 15 kHz so you see it is better to correct a little


see LEOP-LaunchAndEarlyOperation


Our Antennas at the Roof

Our decoder are on way for all of us. Apology for being late but we are busy.

We are working hard on our Blue Box ground station. It is a small - with USB interface - radio for receiving communication from AAUSAT3. It is based on the same ADF radio chip as AAUSAT4.

It is our humble intention to give it away to people who will help us listening to AAUSAT4.

More info about BlueBox here.

Ground Station antenna

Our Ground setup

If you are going to listen for our satellite please drop us an e-mail:

aausat4 AT with subject AAUSAT4 HAM-info and a short explanation of who you are.

At the launch date we will be more than delighted to receive fresh information from you :-) And will of course mention you on this launch web site if you don't mind - just use the email above.

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Page last modified on April 21, 2016, at 09:03 AM EST