A standard 12V power supply or battery connected to a switch mounted on the front panel powers the QROP Meter.
A 1N4001 diode offers reverse polarity protection with only a modest voltage loss (around .5V) for VCC.
Four FB73-101 ferrite beads in series with the 1N4001 diode provide inductance to protect the supply voltages of the op amps from external AC interference that can interfere with their proper operation.
An LED in series with a 1000-ohm current-limiting resistor provides the "idiot light" that shows that the power supply is connected to the rest of the circuit.
The 7805 transistor uses 12V to provide a 5V source for the microcontroller.
The ceramic capacitor for the 5V source should be as close as possible to its respective pins on the microcontroller. The rest of the Power Supply Circuit should share the board with the LM324 amplifier in the Active Rectifier Circuit.
Several decoupling capacitors protect the supply voltages of the op amps from both externally generated and internally generated AC interferenece. Real capacitors have different behaviors at different frequencies. The 100uF, 10uF, and 1uF electrolytic capacitors decouple low frequency interference. The .1uF capacitor decouples high frequency interference and should be placed as close as possible to the leads connecting the VCC and ground pins of the LM324 IC of the Active Rectifier Circuit. Additional .1uF capacitors are used in the SWR Display Circuit and the Wattmeter Display Circuit.
Do NOT add additional lower-value capacitors (such as .01uF or .001uF) with low ESR (internal resistance in series with the capacitance), as this will create more antiresonant frequencies, frequencies at which the impedance between the power supply and ground spikes upward. Thus, the network of decoupling capacitors will fail to work as intended at certain frequencies.
WARNING: Electrolytic and tantalum capacitors are polarized. The positive lead MUST be connected to VCC, and the negative lead MUST be connected to DC ground. Electrolytic capacitors connected with the wrong polarities will pop and make a mess. Tantalum capacitors connected with the wrong polarities will start a fire! Although the 1N4001 protection diode ensures that VCC=0V if the power supply polarity is reversed, the risk of improper polarity still exists in the building stage.