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en:hf_tx_subsys [2019/09/16 15:43]
en:hf_tx_subsys [2020/01/20 11:24] (current)
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-**High-frequency transmitter** \\  +====== HF Radio Link ====== 
-Virtual [[power_subsys|consumption]] ​6100 mA+ 
 +The radio communications system can be included among key systems of the orbiter. However, as is the case with many engineered systems, there is no ideal solution for it. Various designs demand precise trade-offs between data transmission rate and power draw of the orbiter radio equipment as well as between the directional pattern of the orbiter antenna and its efficiency. Every new orbiter design calls for novel approach to the problem of establishing data communications between the orbiter and Earth. 
 +In a run-of-the-mill solution the orbiter would be fitted with low data rate communications equipment for downstream telemetry transfers over the orbiter-Earth link as well as upstream control command transfers over the Earth-orbiter link. As a rule in this case the orbiter is equipped either with an omnidirectional antenna or a system of narrow-beam onboard antennas. A system of this kind enables communications with spacecraft regardless of its orientation and rotation speed; it draws little power but the drawback is insignificant data transfer rate (about 9600 bps). 
 +Another option is to use the orbiter-Earth link with a high-frequency, high data rate transmitter ​with a narrow-beam antenna to transfer payload information to the Earth. This data transfer mode enables data transfer rates in the order of tens and hundreds of megabit per second. On the flip side, such an architecture is power-hungry and requires precise orientation of the orbiter antenna (and hence the orbiter as a whole) toward Earth for the narrow beam to hit a receiver station on the ground.
 {{ :​ru:​вч_канал.png?​400| ВЧ канал}} {{ :​ru:​вч_канал.png?​400| ВЧ канал}}
-The radio communication system is one of the key services of the on-board systems. Howeverlike 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_subsys|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.+==== High-Frequency Transmitter ==== 
 +Virtual power draw: 6100 mA 
 +The high-frequency (HF)high data rate transmitter comes in the construction set as a separate module based on a simple LED with particular blinking frequency and pattern. When light from this “transmitter” is detected by a high-frequency receiver on the ground it is considered that the communications link has been established ​and imagery can be sent from the satellite to Earth (the actual transfer takes place over Wi-Fi). 
 +==== High-Frequency Receiver ====
-The standard solution ​is to install low-speed communications equipment on the satellite to [[uhf_tx_subsys| transmit telemetry]] via the "board-to-Earth"​ line, as well as control commands to the satellite via the "Earth-to-board"​ lineAs a rule, in this case the satellite is equipped with either an omnidirectional antenna or a system of spot beam antennasSuch 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).+The high-frequency (HF), high data rate receiver ​is a part of the construction set that simulates ​the ground receiving station with a high-speed data link. During ​the experimentation stage similar receivers will be mounted directly on the Earth surface i.e. on the globeNevertheless this module should be used for preliminary tests of the “high-speed radio link”.
-Another option is to use a high-frequency,​ high-speed transmitter ​with a spot beam antenna to transmit payload information ​to the  ​[[sim_earth|Earth]] via the "​board-to-Earth" lineThe 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.+This module operates in combination ​with the Mission Control Center (MCC) software. When beam” from the orbiter’s HF transmitter hits the ground HF receiver the latter signals communications link establishment ​to the MCC. It is important that the link is not only established but sustained by stabilizing the “satellite” precisely – only in this case can data be transferred from orbiter’s payload ​to EarthAn important consideration is the quality ​of the communications link that depends ​on the precision of pointing orbiter’s HF transmitter ​to the MCC: displayed ​in the range of to 100 in the top right in MCC software GUI, it tells whether the image can be transferred successfully.
-The high-frequency (HF), high-speed transmitter ​is implemented as a separate module in the construction setand 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 [[sim_earth|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)+<note tip> 
 +**//​Considering that the HF link is designed for “transferring” images from the camerasample code for operating ​the link can be found in the Earth Observation Camera section.//** 
-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.1568637787.txt.gz · Last modified: 2019/09/16 15:43 by golikov