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en:hf_tx_subsys [2017/12/03 15:42]
writer
en:hf_tx_subsys [2020/01/20 11:19]
golikov
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-**High-frequency transmitter** \\  +==== HF Radio Link ====
-Virtual [[power_subsys|consumption]] - 6100 mA+
  
-{{ ru:​hf-transmitter.jpg?​direct&​200|}} +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 itVarious 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.
-The radio communication ​system ​is one of the key service of on-board systems. However, ​like many engineering ​systems ​it does not have an ideal solution. ​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.+
  
-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 and control ​commands to the satellite via the "Earth-to-board"​ line. As a rulein this case the satellite ​is equipped ​with either an omnidirectional antenna or a system of spot beam antennas. ​Such a system ​allows communication ​with the spacecraft ​irrespective ​of its orientation and rotation speed; it consumes low power but also provides small data transfer ​speed (about 9600 bps).+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. ​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 a high-frequency high-speed ​transmitter with a spot beam antenna to transmit ​payload information to the  ​[[sim_earth|Earth]] on the "​board-to-Earth" lineThe data transfer ​speeds ​in this way 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 of the entire satelliterelative to the Earth in order to get the directivity diagram of the on-board antenna to the ground ​receiving station.+Another option is to use the orbiter-Earth link with a high-frequencyhigh 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 wholetoward Earth for the narrow beam to hit a receiver station ​on the ground.
  
-High-frequency (HF) high-speed ​transmitter ​is implemented as a separate module ​in the construction set including ​a simple LED that flashes ​with a specified ​frequency and a certain sequenceAt the moment when the light from this "transmitter" gets on the high-frequency receiver ​to [[sim_earth|the Earth]], ​it is considered that the communication channel is opened ​and it is possible ​to transmit ​the data of photos ​from the satellite to the ground (in reality - via WiFi network)+{{ :​ru:​вч_канал.png?​400| ВЧ канал}} 
 + 
 +==== 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 patternWhen 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 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 globe. Nevertheless this module should be used for preliminary tests of the “high-speed radio link”. 
 + 
 +This module operates in combination with the Mission Control Center (MCC) software. When a “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 “Earth”. An 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 0 to 100 in the top right in MCC software GUI, it tells whether the image can be transferred successfully. 
 + 
 +<note tip> 
 +**//​Considering that the HF link is designed for “transferring” images from the camera, sample code for operating the link can be found in the Earth Observation Camera section.//** 
 +</​note>​
  
-The high-frequency transmitter is one of the main consumers of electricity on board the satellite. It is highly discouraged to keep it permanently on if there is no special need for it: too much load on the power supply system will lead to a quick accumulator slump and emergency deactivation of the "​board"​. 
en/hf_tx_subsys.txt · Last modified: 2020/03/25 16:28 (external edit)