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en:uhf_tx_subsys [2019/09/16 15:46]
golikov
en:uhf_tx_subsys [2020/01/20 11:33] (current)
golikov
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-**VHF transmitter** \\ +====== ​VHF/UHF Radio Link ====== 
-Virtual [[power_subsys| consumption]] ​210mA+ 
 +The VHF/UHF radio link serves for telemetry transfers from the orbiter to Earth. As a rule, the orbiter generates much less telemetry data than the payload it was launched to carry. On the other hand, when orbiter faces a problem threatening loss of its positioning data this link remains available for obtaining critical information on the state of orbiter support systems and restoring the satellite into operation. Moreover the low-rate communications link consumes less energy compared to the HF radio link. 
 + 
 +The VHF/UHF radio link is implemented in the Orbicraft construction set in the form of two modules: the VHF/UHF transmitter module and the ground-based VHF/UHF receiver module. The orbiter-generated dataset comprises a byte array of variable length and arbitrary structure that can be transmitted to Earth along with information on its length. On Earth, messages received during the communications session appear in real time in the MCC software “as is”, meaning that it would be most practical to send telemetry in plaintext.
  
 {{ :​ru:​укв_канал.png?​400|}} {{ :​ru:​укв_канал.png?​400|}}
  
-The spacecraft telemetry transmitter is most often a VHF transmitter ​operating at either ​the 145 or 436 MHz range and providing a low data rate with an omnidirectional or near-omnidirectional ​on-board ​antenna. ​A high data rate is not needed here as the amount of telemetry information from the device ​is usually much lower than the data rate from the payload for which this satellite ​was launched into spaceAdditionally,​ if there are problems ​on-board ​and if the device loses its orientation, ​this communication channel ​will remain available ​in order to obtain critical information about the state of the on-board service systems and restore ​the satellite'​s operability.+==== VHF/UHF Transmitter ==== 
 + 
 +Virtual power draw: 210 mA 
 + 
 +The VHF/UHF transmitter ​of the orbiter most commonly operates at 145 or 436 MHzproviding a relatively ​low data transfer ​rate with an omnidirectional or nearly ​omnidirectional antenna. 
 + 
 +The VHF/UHF transmitter in the Orbicraft Construction Set is numbered 2 (the number is printed on the housing). 
 + 
 +Data is sent to Earth using the function: 
 + 
 +<code c>​int32_t transceiver_send(uint16_t tx_num,​uint16_t rx_num,​const uint8_t *data,uint16_t len);</​code>​ 
 +    
 +==== VHF/UHF Receiver ==== 
 + 
 +The VHF/UHF receiver in the construction set simulates the operation of the receiving part of the ground-based telemetry receiver station over a low-speed link. During experimentation with the “satellite” similar receivers will be mounted directly on the Earth surface i.e. on the globe. However the set also includes this receiver to facilitate preliminary testing of satellite communications. 
 + 
 +The receiver proper interoperates with MCC software. When telemetry data is sent over the orbiter data link and the VHF/UHF receiver is connected in the ground network ​this data will be received automatically by the ground-based receiver and displayed ​in the left pane of MCC GUI. 
 + 
 +The VHF/UHF receiver in the Orbicraft Construction Set is numbered 1 (the number is printed ​on the housing). 
 + 
 +==== A Snippet in C to Test the Telemetry System ====
  
-In case of board abnormalities,​ any and all information is extremely important. The information allows the operational control group that is on duty at the MCC and working with the satellite in communication sessions to identify problems and decide how to solve those problems. In this case, the low-speed communication channel consumes a small amount of [[power_subsys|energy]] in comparison with the [[hf_tx_subsys|HF radio channel]]. 
  
-As part of the construction set, the VHF radio channel is implemented in the form of two modules: the on-board transmitter module and [[uhf_rx_subsys|the ground receiver module]]Data transfer to the ground is carried out using the following function\\  +<file c UHF_Test_C.c> 
-  ​int32_t transceiver_send(uint16_t tx_num,uint16_t rx_num,const uint8_t *data,uint16_t len);  + #include "​libschsat.h"​ 
-Under the experimental conditions the transmitter has the number ​"2" (marked on the body), and [[uhf_rx_subsys|the receiver ​(ground)]] is number ​"1". The array of data transmitted ​from the board to the Earth is a byte array of arbitrary length and composition that can be transmitted to [[sim_earth|the Earth]]indicating its length. On Earthmessages received during a communication session are displayed in real time in the MCC software interface "as is," ​so it is most advantageous to transmit telemetry in text form.+ /* 
 + ** Lab 8UHF transceiver demo. 
 + */ 
 + void control(void) 
 + {  
 + const ​uint16_t tx_num ​= 2; 
 + const ​uint16_t rx_num ​= 1; 
 + const char hello[] = "helloworld!"​
 + printf("Enable transceiver #%d\n", tx_num); 
 + transceiver_turn_on(tx_num)
 + Sleep(1)
 + bus_setup();​ 
 + printf("Send data from #%d to #%d\n"tx_numrx_num); 
 + if (LSS_OK != transceiver_send(tx_numrx_num, (uint8_t *) hello, sizeof(hello))) 
 + puts("Fail!"​);​ 
 + printf("​Disable transceiver #​%d\n",​ tx_num); 
 + transceiver_turn_off(tx_num);​ 
 + return; 
 +
 +</​file>​
  
en/uhf_tx_subsys.txt · Last modified: 2020/01/20 11:33 by golikov