What changed
Electronics basics — edited Aug 31, 2026 by Unknown editor
This is the first recorded version, so every line is shown as added. Note: Imported from content/wiki
+
## Ohm's law
+
+
**V = I × R**, and power **P = V × I**. Rearranged, these answer most exam questions and most
+
practical shack problems — fuse sizing, dropping resistors, supply current.
+
+
## Decibels
+
+
A ratio, logarithmic: **dB = 10 log(P1/P2)** for power.
+
+
- 3 dB = double the power
+
- 6 dB = double the *voltage*, and one S-unit on most receivers
+
- 10 dB = ten times the power
+
- 20 dB = one hundred times
+
+
Going from 100 W to 200 W is 3 dB — barely perceptible. Improving your antenna by 6 dB is worth more
+
than any amplifier you can afford.
+
+
## AC, frequency and wavelength
+
+
**Wavelength (m) = 300 / frequency (MHz)**. A half-wave dipole for 14.2 MHz is about 10.5 m of wire
+
total (with a 5% end-effect correction — hence the 468/f rule in feet).
+
+
## Components in RF
+
+
- **Resistors** dissipate; **capacitors** block DC and pass AC; **inductors** do the reverse.
+
- **Resonance** occurs where inductive and capacitive reactance cancel. Every antenna, filter and
+
tuned circuit is an application of this.
+
- **Impedance** is AC resistance; 50 Ω is the amateur standard for feedline and equipment.
+
+
## Semiconductors
+
+
Diodes rectify; transistors amplify or switch. Modern transceivers use them in the hundreds of
+
thousands, but the exam only asks you to recognize symbols and basic behavior.
+
+
## Safety numbers worth remembering
+
+
Currents as low as **100 mA across the chest** can be fatal. RF burns are deep and slow to heal.
+
Capacitors in tube amplifiers hold lethal charge long after power-off — do not open one without
+
knowing how to discharge it.