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The resource details the construction of a homebrew 50-watt FET amplifier, based on Don W6JL's _QST Homebrew contest_-winning design from 2009. It functions as an afterburner for QRP transceivers, providing a **12dB** power lift. The amplifier utilizes IRFZ24N FETs and covers the 80, 40, 30, and 20-meter bands, with the 20m LPF extending to 17m. Key technical aspects include an FT37-43 transformer for the input network, a relay-switched 3dB pad for lower bands controlled by an _Arduino Nano_, and an RF-actuated T/R switch. The LPF board integrates four relay-switched filters rated for 50 watts, using capacitors with a minimum 250VDC rating. Performance measurements indicate a power gain ranging from **4.4dB** on 20m to 8.1dB on 80m, with a required drive power of approximately 5 watts. The article also discusses thermal management, current limiting considerations, and component sourcing.

An HF 10-20m portable RF power amplifier based on the RD16HHF1 FETS giving 25 W.

This resource details **cooling modifications** for Ameritron AL82, AL1200, and AL1500 HF amplifiers, specifically addressing heat issues encountered during high-duty-cycle digital mode operation. The author, WD4NGB, observed excessive heat in the tank area and band switch on an AL82, attributing it to insufficient exhaust over the 3-500 tubes and a complete lack of exhaust over the tank area. The modifications aim to prevent common failures such as damaged band switches and deformed insulating materials by increasing airflow and exhaust area. The page describes adding five holes to the chassis for enhanced cooling to the band switch and tank area, alongside enlarging the exhaust area over the inner 3-500 tube and the tank area on the amplifier cover, utilizing expanded metal for safety and RF shielding. The original cover featured 26.25 square inches of exhaust; the modified version significantly increases this to 48.5 square inches over the tubes and introduces an additional 15 square inches over the band switch. These changes are intended to resolve heating problems encountered during heavy, 100% duty cycle use in modes like RTTY or long SSB contests, which typically generate substantial heat. The article also discusses upgrading to a higher output fan, such as the G2E085-AA05-21, and modifying tube sockets for improved airflow and reduced back pressure, citing Tom Rauch (W8JI) of CTR Engineering as a source for parts.