Search results

The Spartan Sprint Special 40m CW Transceiver, originally documented in 2002 and reproduced in 2019, details a **QRP** direct conversion rig designed for portable operation. This project evolved from an experimental CMOS digital IC receiver, which proved too noisy for weak signals, into a dedicated 40-meter CW transceiver. The author, VE3SMA, aimed for reduced size, lower weight, and decreased receive current drain compared to earlier iterations, drawing on his extensive contesting experience and even his time operating million-watt transmitters at Radio Canada International. This compact transceiver delivers approximately 200 mW output, VFO-tunable over 15 kHz within the 40m band, and weighs a mere 73 grams (0.16 lb) including its balsa wood case. It features fast semi-break-in and sidetone, with a receive current draw of about 14 mA (no signal) and transmit current draw around 125 mA key down. The design incorporates various construction techniques, including knife-cut surface mount boards and through-hole components, often salvaged from junked cordless phones and cellphones. Despite its direct conversion architecture, which offers usable but not superheterodyne-level selectivity, the rig proved effective, achieving a fourth-place finish in a June 2001 Spartan Sprint contest when paired with a 26-foot vertical antenna. The article provides comprehensive circuit details, including an unconventional VFO using a high-speed CMOS inverter chip and a balanced mixer utilizing a 74HC4053.

The article details the repair of an Elecraft K3 transceiver experiencing an "ERR 12V" issue, causing reduced output power. The problem, common in these units, stems from inadequate pin strips carrying high DC current to the PA unit, leading to overheating and poor conduction. The author identified the faulty connectors and implemented a bypass using existing PCB pads, effectively rerouting the power and resolving the error. This straightforward fix highlights the importance of robust electrical connections in high-current applications, restoring the K3's full functionality.