AMSAT-UK

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Another EO-79 Transponder Activation

Posted: 28 Dec 2015 04:01 AM PST
http://amsat-uk.org/2015/12/28/anoth...79-activation/

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

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 http://isispace.nl/HAM/qb50p.html

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.

TLEs:

AMSAT keps name: EO-79

Celestrak keps name: QB50P1

Celestrak file: cubesat.txt

NORAD #Â* 40025

COSPAR designator: 2014-033-R

SatPC32 tracking software Doppler SQF information used by Peter VK4NBL:

EO-79,145950,435063,USB,LSB,REV,0,0

EO-79,145814.8,435070,CW,TELEMETRY,0,0

PE0SAT http://www.pe0sat.vgnet.nl/

https://www.facebook.com/pe0sat/

https://twitter.com/pe0sat

Real-time track of EO-79 (QB50p1) http://www.n2yo.com/?s=40025&df=1

Satellite Tracking http://amsat-uk.org/beginners/satellite-tracking/

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