Numerous transmitters may actually share the same frequency and
proximity, but they coexist only because of the brevity and low
repetition rate of transmissions. Minimal information is transmitted
–this consists of (8) bits of identification plus (4) additional bits of
identification or variable control data.
The low data rate (4800 bits per second) is acceptable for identification and limited control with a typical (4) byte transmission requiring only 8mS. The protocol in this ASK ‘party line’ environment is very simple: first come, first serve, loudest or closest gets heard. Receiver address security is high, but transmission reliability is somewhat compromised by RFI (Radio Frequency Interference) and potential collisions where more than one transmitter may be transmitting simultaneously. Due to these limitations, the operator must occasionally push the button a 2nd time to open a door etc.
This discussion builds upon the previous (excellent) work of T.K. Hareendran: RF Based Wireless Remote Control System. It is limited to the transmitter and super regenerative receiver, but not the super heterodyne receiver as that piece has yet to be delivered –the results of testing this piece will be included as a subsequent comment. Future work will include an evaluation of the Holtek encoder /decoder devices that are required to complete the system.
Photo of transmitters and receivers
The low data rate (4800 bits per second) is acceptable for identification and limited control with a typical (4) byte transmission requiring only 8mS. The protocol in this ASK ‘party line’ environment is very simple: first come, first serve, loudest or closest gets heard. Receiver address security is high, but transmission reliability is somewhat compromised by RFI (Radio Frequency Interference) and potential collisions where more than one transmitter may be transmitting simultaneously. Due to these limitations, the operator must occasionally push the button a 2nd time to open a door etc.
This discussion builds upon the previous (excellent) work of T.K. Hareendran: RF Based Wireless Remote Control System. It is limited to the transmitter and super regenerative receiver, but not the super heterodyne receiver as that piece has yet to be delivered –the results of testing this piece will be included as a subsequent comment. Future work will include an evaluation of the Holtek encoder /decoder devices that are required to complete the system.
Photo of transmitters and receivers
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