Free, instant, and 100% in your browser — no signup, no app. The same kind of math built into every Hood's Finds guide. Bookmark this page for the bench.
Cut length for a half-wave dipole, quarter-wave vertical, or full-wave loop. Includes the end-effect correction so your antenna lands close to resonance on the first cut.
468 / f · Vertical 234 / f · Loop 1005 / f (length in feet, f in MHz)Enter forward and reflected power from your wattmeter to get SWR, return loss, and the percentage of power bouncing back. Anything under 1.5:1 is a clean match.
SWR = (1+ρ)/(1−ρ)Enter any two of voltage, current, resistance, or power and get the other two. The workhorse calculation for power supplies, bias networks, and dummy loads.
V = I×R · P = V×I · P = I²×RFind the resonant frequency of a tank circuit from inductance and capacitance — essential for tuned output networks, traps, and matching sections.
f = 1 / (2π√(L×C))How much gain is your amp really making? Enter drive power in and RF power out to get gain in decibels — the honest way to compare amplifiers.
Gain(dB) = 10 × log₁₀(Pout / Pin)Convert RF power between watts and dBm in both directions — handy for spec sheets, signal generators, and link budgets.
dBm = 10 × log₁₀(W × 1000)These six are the free sampler. The full Calculator Tools Bundle packs 51 interactive tools — impedance matching, load lines, coil winding, filter design, enclosure tuning, transformer ratios and more. Works 100% offline, forever.
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Search any RF final — 2SC2879, 811A, LDMOS, 3-500Z — and see which legendary builders ran it, the amp classes it runs in, and its power range.
Open the Cross-ReferenceTransistor substitution tables, bias cheatsheet, common impedance values, and the 10 mistakes that kill amplifiers. Plus the occasional new-build email. No spam, unsubscribe anytime.