THE HANDS-ON HAM RADIO LAB
Follow the signal.
From your transmitter to the air.
Build a station, turn the knobs, and see where the power goes.
01Your signal chain
02Turn the knobs
COMPONENT SETTINGS03Along the feedline
04The antenna up close
IDEALIZED WIRES / REAL FEEDPOINT NUMBERSWire shapes, current and voltage distributions, and radiation patterns are the textbook sketches for each antenna preset — not geometry simulations. They track the operating frequency around each preset's 14.2 MHz design point: tune below it and the wire becomes electrically short, above it the standing wave splits into phase-reversed sections. The feed point voltage, current, impedance, and V/I phase come from the actual station model above, where the load impedance itself stays fixed.
NOT LOST. ACCOUNTED FOR.
Every watt has a destination.
iA small model of a big subjectThe math & assumptions
Power on the way out
A matched line reduces forward power by Pout = Pin × 10−L/10, where L is cable loss in dB. Preset losses are approximate values at 10 MHz, scaled by √(f / 10 MHz). This is an illustration, not a cable datasheet.
We include loss on both the outward and reflected waves. Connector losses, weather, radiation from feedlines, and heating-related changes are omitted.
When impedances disagree
At a load, Γ = (Zload − Z₀) / (Zload + Z₀) and SWR = (1 + |Γ|) / (1 − |Γ|). Forward and reflected waves add to create voltage and current patterns. Cable electrical length and velocity factor affect the impedance seen at the transmitter.
The plots show RMS magnitudes along a line, not instantaneous RF oscillations. SWR at the TX can look better simply because a lossy cable attenuates the returning wave — the SWR view shows that decay directly.
Ideal parts, useful lessons
The transmitter is a matched source that absorbs returning power, with no SWR foldback. Its optional antenna tuner mimics a built-in auto-tuner: relay-switched banks in 10 pF and 0.2 µH steps over a finite range, in either L-network orientation, found by a coarse-then-fine search. It stays lossless — no coil resistance, stray capacitance, or switching transients. Amplifiers have fixed gain, a forward-power cap, matched resistive ports, and no reverse coupling. DC consumption and amplifier efficiency are not modeled.
Transformers are lossless: Zin = Zload / ratio. Balun and unun choices here only describe impedance ratios; balance and common-mode current are not simulated.
An antenna, simplified
An antenna is a lumped R + jX load. Presets are illustrative feedpoint values, not geometry simulations. Changing frequency changes the feedline, but does not retune the antenna impedance. Set R and X yourself to explore a different operating point.
Radiated power is accepted feedpoint power times the chosen efficiency. No computed radiation patterns, bandwidth prediction, or ground system — the antenna view draws textbook wire sketches and patterns instead. Positive X is inductive; negative X is capacitive.