The mating connector to J3 has an associated coax cable with a barrel connector at the other end that can be plugged into the oscilloscope. Since the barrel is connected to Earth GND via the oscilloscope, the J3 connector on the board was taken out and repositioned so that the GND connection gets connected to the GND barrel, as can be seen from the schematic. A 20-kHz pulse, with a LOW of 0 V and HIGH of 3.3 V, was used to provide an adjustable PWM signal to control the output voltage, referenced to GND. A 3.3-V signal voltage was used to enable the device via the Enable connector, referenced to GND.

The output ripple voltage was measured by another connector placed at the end of a blank copper clad board, to keep the measurement point away from the switch node. The original location, that is, where J3 is located, is too close to the switch node and so a lot of noise is being injected into the connector. The end of the copper clad board simply has a 100-µF and 1-nF capacitor close to the antenna connector where the measurement is made.