To talk about HAM radio electricity basics, you must know some basics of electricity. If you haven’t already obtained your Technician class license, you’ll need to know the basics to pass the first test and be able to do some math. Electricity begins with current, resistance, voltage and Ohm’s Law.
In the simplest circuit, you might have a voltage source hooked up to a wire with a resistor set in line. A closed circuit is a circuit where current can flow uninterrupted. If the circuit opens up, the current stops flowing and the electronic device won’t work anymore.
Voltage is an electrical circuit power source. Voltage works by pushing electrons through the circuit. The moving of the electrons is called current and is measured in Amperes.
A resistor works by turning electrical energy into heat which decreases the amount of energy running through the circuit. There are many different kinds of resistors offering different resistances and can be added in combination to obtain a desired result. Resistance is measured in Ohms.
Ohm’s law states that current is directly proportional to the voltage of the circuit and inversely proportional to the resistance in a circuit. As resistance increases, current decreases. Another way to state Ohm’s law is V = IR, or voltage equals current multiplied by resistance.
Power is measured in Watts. You may be familiar with wattage and know how much power you need to supply to some of your own equipment. We will now learn about power and how it relates to your electronic components.
Power quantifies the rate of energy transfer. Power is equal to voltage multiplied by current in a circuit. Voltage produces power while whatever is connected in the circuit absorbs it.
An example would be a lamp. A wall socket is providing 120 volts to a lamp that houses a 60 watt light bulb, you can then determine that the lamp is drawing .5 amps of current. To calculate the resistance of the light bulb, you would simply use Ohm’s law (V = IR) which would equate to 120V/.5A = 240 ohms of resistance.
HAM radio enthusiasts are limited to transmitting a max of 1500W PEP and technician class HAMs are limited to 200W PEP. More power from your transmitter and antenna mean your signal will have the ability to go farther in distance.
Alternating Current vs Direct Current
There are two types of current, alternating and direct current. The type of current that comes from a wall socket is an example of alternating current but the kind of current that comes from a battery would be an example of direct current.
With direct current, the current is always flowing in the same direction from the negative to the positive terminals. These terminals always remain negative and positive. The current pretty much flows in a big circle.
Alternating current is a little bit different. The current alternates direction 60 times per second (in the US, in Europe it’s 50 times per second). Alternating current makes it easier for power companies to “step down” the voltage, meaning they can send current out at very high voltages and then step it down with a transformer so that it can be useful to your house.
Electricity in Radio
We know that your antenna will convert the electromagnetic energy into an alternating current which will then be fed into your radio receiver. But what does your radio do with the alternating current?
The alternating current that is at the same frequency as the radio wave it picked up will come into your receiver which is made up of a coil and a capacitor. A capacitor is an electronic component that has the ability to store energy. Inductors are also added to a circuit to work with a capacitor in efforts to tune your circuit to the desired receiving frequency.
The circuitry is designed to work better at the specific frequency that you desire and you can change the desired frequency by changing, or tuning, your circuit. This can be done by varying the inductance and capacitance in the circuit. The formula for calculating frequency based on inductance and capacitance is where L is the inductance of a circuit and C is the capacitance of the circuit.
After the signal is picked up, it goes through a diode which demodulates the signal. A diode conducts current in one direction and converts alternating current to direct current. The demodulated signal gets fed to an amplifier which produces audible audio signal.
You can change the tuning of your radio receiver to a desired frequency. All that is doing is adjusting the electronic components to find the resonant frequency. If the antenna picks up that particular frequency, the signal will be allowed to come into the circuit to be processed.
The signal is then turned from AC to DC by a diode. This is the process of demodulation and turns the signal into something we will be able to listen to and comprehend.
This is a very basic overview of electronics and the electronics in radio.