PA Board

The picture below was taken at the end of October 2010, and is of the prototype Power Amplifier (PA) board in a ‘very nearly’ completed state. There are a few components to add, the values of which must be determined as they are installed – a time-consuming process. Thanks to David, G0MRF, for these pictures!

This board contains a 145 MHz linear amplifier based on the Mitsubishi RD02MUS1 radio frequency (RF) power MOS FET.

The board amplifies the transponder and telemetry signals which are generated on the RF board and then passes them to the antennas.

In addition to the amplifier, the PA board contains a low pass filter which has resonant traps for the third harmonic from 145MHz, which at 435MHz is very close to the transponder input frequency.

The board also contains 4 points of telemetry gathering. These are PA device input current, RF forward power, RF reverse power and PA device case temperature.

The 4 channels of telemetry are sampled by a 4 channel A-D converter and then sent to the CCT board via an I2C interface.

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