70MHz Transmit Converter GW4RWR

Introduction
The prototype board had been bolted directly to the main transceiver chassis, access was difficult. This module was enclosed in a recycled diecast box to enable straightforward removal for testing or modifying. The box lid was already drilled to support four N-sockets, and has been bashed a bit more to access the trimmers and to allow the PA heatsink to poke through.

A variable resistor on the front panel controls the IF drive into the transverter. The mixer is a pair of BF256 in push-pull, then a two pole bandpass filter, followed by a BF961 driving a MRF237

Results
Local oscillator power was varied to establish that about 100uW of drive is required. A similar I.F. power is needed for 1W output. The MRF237 provides plenty of gain, since the output from the preceeding mosfet stage was measured at just a few mW.