A Narrowband SDR Transceiver for Amateur Radio Applications: Hardware Design and Construction
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A VHF radio transceiver targeted for maximum efficiency and flexibility in CubeSat- and UAV applications has been designed, constructed and tested subsystem by subsystem, and ultimately as a complete system. The best case receiver sensitivity has been measured to be approximately -120 dBm at 1 % bit error rate using 9600 baud GMSK modulation while consuming 80 - 132 mW of DC power depending on input voltage. The transmitter section has been designed for constant envelope modulation with maximum efficiency over a large output power span. By using a switch mode power supply and dynamic biasing for the final PA, the total efficiency calculated from DC input to RF output at 8 V supply voltage was measured to be 53.0 %, 45.8 % and 17 % at approximately 5 W, 1 W and 0.1 W output power, respectively. Testing with 9600 baud GMSK modulation confirmed spurious emissions to be well within current regulations from ITU.