Design of a 7-MHz Portable Direct Conversion Transceiver with Digitally Controlled Keying
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".