What is 50 Ω and why is it everywhere?
50 Ω is the industry standard characteristic impedance for RF coaxial cable and most RF equipment. It's a compromise: 30 Ω gives minimum loss in air-filled coax, 77 Ω gives maximum power handling. 50 Ω splits the difference and became the standard through historical convention in military radar work. When all your equipment is 50 Ω, you minimize reflections at every connection.

What does dBm mean?
dBm is power measured in decibels relative to 1 milliwatt. 0 dBm = 1 mW. Every +3 dB doubles power, every −3 dB halves it. Typical RF values: Wi-Fi transmitter ≈ +20 dBm (100 mW), received Wi-Fi signal ≈ −70 dBm (100 picowatts). The dBm scale lets you add gains and losses instead of multiplying ratios. Try the converter →

What is the Smith Chart?
The Smith Chart is a graphical way to plot complex impedance (resistance + reactance) on a single circular diagram. Every point inside the circle corresponds to one impedance value. Moving along transmission lines traces arcs on the chart. Matching networks move points toward the center (50 Ω). It looks intimidating but becomes intuitive with practice. Try the interactive version →

Why does skin depth matter?
At RF frequencies, current flows only near the surface of a conductor, not through its full cross-section. The skin depth δ = √(2/ωμσ) is the depth at which current falls to 1/e of its surface value. At 1 GHz in copper, δ ≈ 2 µm. This means your conductor only needs to be a few skin depths thick — but if it's plated or corroded, those surface layers dominate resistance and loss. Calculate skin depth →