F-120-4A includes the F-120-4 and a "matching network". The matching network is used to change impedance of the F-120-4 to a nominal 50 W between 10 KHz and 2 MHz reducing the amplifier input power required to perform the testing. The F-120-4A has the same useable frequency range as the F-120-4, 10 KHz to 175 MHz, and an insertion loss less than 12 dB over the greater frequency range of 80 KHz to 150 MHz. The higher efficiency increases the CW input power rating to 200 watts from 10 KHz to 2 MHz.