The T03DSP High Performance Transceiver with DSP IF processing

The Power Amplifier Board

The three stage power amplifier uses a common techniques to archive the necessary parameters.

The first two stages operate in class A and the third - AB. I used Russian transistors designed specially for the linear amplifiers.

The design goal was to get 10W of an exceptionally clean signal (for using with external linear) and 20-25W with usual parameters for 12V amplifiers. Here are the results:

Output power	IMD3 below PEP	IMD5 below PEP
10W	42 dB	58 dB
20W	29 dB	52 dB

I have optimized final stage quiscent current for the minimal fifthorder intermodulation distortion (IMD5).

The spectral display of the T03DSP transmitter during twotone intermodulation distortion (IMD) testing on HF. The worst-case third-order product is approximately 42 dB below PEP output, and the worst-case fifthorder is approximately 58 dB down. The transmitter was being operated at 10 W output at 3.600 MHz.

The spectral display of the T03DSP transmitter during twotone intermodulation distortion (IMD) testing on HF. The worst-case third-order product is approximately 29 dB below PEP output, and the worst-case fifthorder is approximately 52 dB down. The transmitter was being operated at 20 W output at 3.600 MHz.

The schematics of the power amplifier board is here.