This UHF RF Amplifier operates between 430MHz and 470MHz and will output approximately 20Watts of RF power from a 10mW input source. Apart from the obvious, amplifying a 70cm HAM signal, this amplifier can be used as part of a 457MHz pager transmitter.
This power amplifier is built around a 20 Watt hybrid power module.
These modules are offered by various manufacturers and can often be obtained second hand of amateur rallies. Most hybrid modules require an input power of 20dBm. Therefore, a driver stage before the hybrid module input is incorporated.
The PA module suppresses output harmonics through an internal filter. As almost all components are SMD, the use of hollow rivets is unavoidable if the ground plane on one side and the ground tracks on the other side of the PC board is not interconnected. The O/P coil consists of 9 windings of 1mm silver plated copper wire, wound 7mm in diameter. Carefully fit the amplifier board to a heat sink and position the module to it. Check if it fits properly, then remove the module and smear a thin, uniform layer of heatsink compound on the mating face of its metal flange, but do not use heat sink compound if the module has no ground separate connectors to the PC board.
This page was updated on 12th January 2001.