This project explored the feasibility of creating a cost-effective transmitter receiver pair to replace commercially available 150 MHz devices used in animal telemetry. Distance measurements of test circuits transmitting at 418 MHz were taken over clear ground and in forested areas. These measurements show a range of 300-400 feet in forest underbrush and acceptable dropoff over distance, demonstrating that 70 cm radiation can be used in this application. For testing, a 418 MHz Yagi antenna was constructed and shown to exhibit strong directionality and approximately 20 dB gain in the forward direction.
Once it was determined that 400 MHz radiation is capable of forest penetration to the range specified, the telemetry transmitter design was optimized for greater battery life. After exploring several potential oscillator designs for transmitter input, an op-amp circuit was designed with appropriate PCB layout. A 433 MHz transmitter/receiver pair was constructed and tested to show signal range at the same level as earlier measurements at significantly lower power consumption rate. The final transmitter has a total current draw of 70 uA. This translates to roughly one and a half months of continuous operation using freely available 70 mAh lithium-ion coin batteries. Components for the transmitter receiver pair are available at considerably less cost than commercial devices, with component cost for each transmitter at roughly ten dollars and for the receiver at less than twenty dollars.
Original document Wireless Telemetry: Christopher Yeou - Hwa Chau
Once it was determined that 400 MHz radiation is capable of forest penetration to the range specified, the telemetry transmitter design was optimized for greater battery life. After exploring several potential oscillator designs for transmitter input, an op-amp circuit was designed with appropriate PCB layout. A 433 MHz transmitter/receiver pair was constructed and tested to show signal range at the same level as earlier measurements at significantly lower power consumption rate. The final transmitter has a total current draw of 70 uA. This translates to roughly one and a half months of continuous operation using freely available 70 mAh lithium-ion coin batteries. Components for the transmitter receiver pair are available at considerably less cost than commercial devices, with component cost for each transmitter at roughly ten dollars and for the receiver at less than twenty dollars.
Original document Wireless Telemetry: Christopher Yeou - Hwa Chau
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