The TBMDA4 modulated wideband power amplifier is designed in order to create an inexpensive signal source for immunity testing of electronic building blocks and products. It is designed to be driven by the tracking generator output of spectrum analyzers. With an input power range of -5 dBm…0 dBm, it can boost the output power of a tracking generator up to 5W. With a frequency range from 100 kHz to 50 MHz, it is an ideal complement to the TBMDA3, which covers 10 MHz to 1 GHz. The TBMDA4 is ideal to drive Tekbox near field probes in order to find the sensitive spot of an electronic circuit or to create electric fields up to 550V/m when driving the Tekbox TEM Cell TBTC0, 300V/m when driving the TBTC1, 150V/m when driving the TBTC2 or 100V/m when driving the TBTC3. Test signals for immunity testing can be CW, AM or PM modulated. Consequently, the TBMDA4 provides built in modulation capability to generate 1 kHz AM or PM signals. In PM mode, the TBMDA4 can also generate a 217 Hz Signal with 12.5% duty cycle in order to simulate mobile phone TDMA noise.