Sallesat’s CW Beacon has the responsibility of transmitting a permanent signal and other telemetry satellite data. The Beacon will be operating the whole orbit cycle and will not depend on any other satellite systems. In order to keep it working, only a power supply (+3.6V) and an antenna will be needed.
The beacon has been designed for a full autonomy and needs only a power source, a connection with the battery’s charge sensor, another one with a 4 bits bus that shows the computer status and an antenna connection. So, if there is any malfunctioning of any satellite’s subsystems, the beacon will be always on and the basic telemetry could be received and will inform us of the status of several satellite parameters. This will allow us to determine which subsystem is failing.
In order to keep beacon transmitting power as low as possible and signals received by as many radioamateur stations as possible, the beacon will transmit in CW (A1a) and data will be Morse coded.
Initial design specifications:
Band: UHF in a frequency to be determined (435-438 MHz)
ransmitting power: 100 mW (+20 dbm)
Speed transmission in CW: 10ppm (50 characters per minute)
Very simple transmitter design for minimizing failures
Four telemetry channels with two or three resolution digits
One telemetry channel with only one digit, between 0 to F (hexadecimal) that will show one of 16 different computer states.
The Analogical/digital parameter converters will be placed on the same beacon board.
Power supply with 7 V coming from the battery through a dc/dc converter.
The telemetry channels will be sending the following parameters:
N1: Battery tension in Volts (3 digits)
N2: Beacon board temperature (ºC). It’ll be detailed in 2 digits preceded by a letter (P or N) that will show its positive or negative value
N3: Beacon transmitting power in dBm (2 digits)
N4: Computer status (4 bits). Transmitted in a digit with 16 possible status (0-F)
N5: Battery charge intensity in mA (3 digits)
The message format will be as follows: =SALLESAT1 N1 N2 N3 N4 N5 =
Where N1 to N5 meaning the telemetry channel transmitted by the beacon with message to be retransmitted every 10 seconds.
Parameters are read all at the same time to be sent later.
For getting a power transmitted lecture, a pulse will be sent at the beginning of each frame.
In order to facilitate the reception of data, they will be actual value and no any conversion formula will be needed.
If power tension from the battery decreases, the beacon will transmit messages at greater intervals to allow energy savings.
These specifications could be changed, depending of the tests to be made later with the circuit.
Beacon diagram modules:
Satellite modules diagram where beacon interconnections have been detailed.