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en:hf_tx_subsys

High-frequency transmitter
Virtual consumption - 6100 mA

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The radio communication system is one of the key services of the on-board systems. However, like many engineering systems it does not have an ideal solution. When designing each device, you need to search for a balance between the data transfer rate and the power consumption of the on-board radio equipment, as well as between the width of the antenna directional pattern and its efficiency. Each new satellite project requires special approaches to solve the problem of data exchange between the board and the Earth.

The standard solution is to install low-speed communications equipment on the satellite to transmit telemetry via the “board-to-Earth” line, as well as control commands to the satellite via the “Earth-to-board” line. As a rule, in this case the satellite is equipped with either an omnidirectional antenna or a system of spot beam antennas. Such a system allows for communication with the spacecraft irrespective of its orientation and rotation speed; it consumes low power, but also provides a low data transfer speed (about 9600 bps).

Another option is to use a high-frequency, high-speed transmitter with a spot beam antenna to transmit payload information to the Earth via the “board-to-Earth” line. The data transfer speeds using this option are tens and hundreds of megabits per second. However, such equipment consumes more power and requires precise orientation of the on-board antenna (and hence, the entire satellite) relative to the Earth in order to get the directional pattern of the on-board antenna to the ground receiving station.

The high-frequency (HF), high-speed transmitter is implemented as a separate module in the construction set, and includes a simple LED that flashes with a specified frequency and a certain sequence. At the moment when the light from this “transmitter” is received by the high-frequency receiver on the Earth, it is considered that the communication channel is open and it is then possible to transmit the data (photos) from the satellite to the ground (in reality - via WiFi network).

The HF transmitter is one of the main consumers of electricity on board the satellite. It is highly discouraged to keep it on permanently if there is no special need for it. Too much load on the power supply system will lead to a quick battery drainage and an emergency deactivation of the “board.”

en/hf_tx_subsys.txt · Last modified: 2019/09/16 15:43 by golikov