Delfi-C³ Communication Subsystem

The communications subsystem (COMMS) provides the telemetry downlink and telecommand uplink functionality. Besides that, it provides a linear transponder service which can be used by amateur radio operators to communicate with each other. The satellite has an uplink in the satellite segment of the UHF amateur radio frequency band (435-438 MHz) and a downlink in the satellite segment of the VHF amateur radio frequency band (145.8-146.0 MHz). Telemetry downlink is done using 1200 bit/s BPSK modulation and the amateur standard AX.25 protocol. Telemetry is packed in AX.25 frames.

The COMMS consists of two Radio Amateur Platforms (RAPs) which are almost identical, except that the primary has a linear transponder and the secondary not. The RAPs are built using standard commercial-off-the-shelf components.The linear transponder will relay a 40 KHz wide passband from the UHF band to the VHF band. This provides a very flexible system, which can be used by amateur radio operators worldwide using CW, SSB and PSK31 modulation. Unfortunately the transponder functionality has deceased after a few months of succesfull operations.

The antenna subsystem consists of a two canted turnstile arrangements, one for each band. The antennas are fed in quadrature phase in order to achieve the desired pattern and polarization by means of a phasing circuit, which connects to both transceivers. The antennas are stowed in launch configuration in a modular antenna box. The eight antenna are safely deployed in orbit, by melting a restraining wire on command by the onboard computer.