Another EO-79 Transponder Activation

EO-79 Passband - Credit Jan van Gils PE0SAT

EO-79 Passband – Credit Jan van Gils PE0SAT

The EO-79 CubeSat SSB/CW transponder will be active from Monday, December 28 until Thursday, December 31.

The first activation has shown the transponder uplink is about 12 kHz higher than expected. The suggested frequencies to try are now:
Uplink: 435.047-435.077 MHz LSB
Downlink: 145.935-145.965 MHz USB

EO-79 and EO-80 - Image Credit ISIS

EO-79 and EO-80 – Image Credit ISIS

The team has seen that activating the transponder makes the satellite power negative, meaning the solar arrays cannot generate enough power to keep the transponder running permanently. This is not unexpected as the satellite is operating in a different mode than originally anticipated during the design phase.

The team are discussing various ways to solve this, including multiple ways of scheduling the transponder operations. With these discussions ongoing we would still like to try the second activation and obtain some more data about the system. The team aim to activate the transponder for as much time as the power budget allows, but please be aware that you may find the transponder to be off while the batteries recharge.

EO-79 has been set to only beacon the normal AX.25 beacon every 30 seconds instead of 10 seconds. The beacon frequency is 145.815 MHz and consists of AX.25 frames on BPSK. More details about the downlink can be found on the ISIS Ham Radio page at

We kindly request you to share your experiences with the AMSAT Bulletin Board so everyone can benefit from operating tips and tricks, as well as being up-to-date on the status.

We would also welcome any observation related to the transponder behaviour when the AX.25 beacon comes on.

Just like FUNcube-1, the crystal oscillator circuits exhibit drift with temperature. This means manual tuning will probably work best.

Graham Shirville G3VZV says that due to platform sharing considerations the FUNcube transponder on EO-79 uses 1/4 wave monopole antennas rather than the full dipoles used on AO-73. The actual effects of this difference in practice may be interesting to observe.

AMSAT keps name: EO-79
Celestrak keps name: QB50P1
Celestrak file: cubesat.txt
NORAD #  40025
COSPAR designator: 2014-033-R

SatPC32 tracking software Doppler SQF information used by Peter VK4NBL:


Real-time track of EO-79 (QB50p1)

Satellite Tracking

AMSAT Bulletin Board (AMSAT-BB)