Portland State University. Department of Electrical and Computer Engineering
Term of Graduation
Date of Publication
Master of Science (M.S.) in Electrical and Computer Engineering
Electrical and Computer Engineering
Radio -- Transmitter-receivers -- Design and construction
1 online resource (ix, 70 pages)
This thesis outlines the design of a portable direct conversion transceiver system for the 7-MHz (or 40m) band. This band is popular due to its propagation characteristics which allow for world-wide communication with very low power. The transceiver utilizes a crystal-stabilized local oscillator optimized for frequency agility, low power consumption, and an optimal drive level of +7 dBm. A low power 8-bit microcontroller acts as an interface for either a straight key providing manual Morse code operation or digital logic control from a personal computer. It also acts as a side tone oscillator providing audio feedback to the operator during keying and reducing circuit complexity. Switching field-effect transistors (FETs) were used to change from transmit to receive with a switching speed of less than 300 microseconds and allowing for full break-in functionality. For the transmitter portion of the design, a dual-stage power amplifier was developed capable of power output levels greater than 30 dBm. Transmission tests were received at several locations ranging from Calgary, Canada to Tucson, Arizona having a maximum propagation distance of 1103.5 miles from the transmitter source.
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Morphew, Abram, "Design of a 7-MHz Portable Direct Conversion Transceiver with Digitally Controlled Keying" (2020). Dissertations and Theses. Paper 5548.