Dartsat's entire communication system resides within the amateur radio bands - a fertile ground for experimentation and novelty. It has a 146 MHz FM uplink and a 440 MHz FM downlink. These frequencies were chosen since they travel line of sight thousands of miles through space, and they will enable many people to use existing HAM gear to communicate with the satellite. The satellite will identify itself every 5 minutes in Morse Code with the callsign "W1ET" which is from the Dartmouth Amateur Radio Club. Ground users can activate/deactivate the satellite and collect data from the satellite by sending up a series of DTMF tones (standard telephone touch tones). The device will also act as a single channel VHF/UHF "repeater" enabling two people thousands of miles apart on earth to be able to communicate via the satellite using low power (~ 5 watts).
The receiver and transmitter will use two omnidirectional dipole antennas which are pendicular to one another. The details about their deployment is included under the mechanical section.
The satellite's receiver is crystal controlled. It operates on 146 MHz, has a 5 kHz bandwidth and a 0.1 uV sensitivity. The entire dual conversion superhetrodyne system (local oscillators, mixers, and demodulator) is built into a single Motorola MC13135 IC which requires 4.8 VDC, 5 mA to operate. All the parts will be space rated (ie. operate over wide temperature ranges, survive extreme mechanical vibration, and are radiation hardened). These surface mount parts are rigidly mounted on a custom built printed circuit board.
The satellite's transmitter is also crystal controlled. It operates on 440 MHz with a 5 kHz bandwidth and maximum of 0.5 W RF output. All the basic components (current controlled oscillator, multiplier and phase detector) are housed in a single Motorola MC13176 IC. The power amplifier is basically a single RF2117 IC from RF Micro Devices. The entire transmitter requires 3.0 VDC, 500 mA making it about 30% efficient. Like the receiver, all the parts are space rated, surface mount, and stuffed into a custom built printed circuit board.
For further information please contact Todd E. Kerner.