Gainwright RF Calculator

Gainwright is an RF, telecom and live-sound calculator for tower and microwave link technicians, two-way radio and cellular installers, ham operators, and live-sound and system engineers. It works like a hardware calculator: a matte black chassis, real keys and a clear LCD, with each answer labelled so you know what you are reading.

ANTENNAS

• Frequency to wavelength and back (146.52 MHz: 6 ft 8 9/16 in, or 2.046 m)

• Half wave, quarter wave, the 468/f half-wave dipole (3 ft 2 5/16 in, each leg 1 ft 7 3/16 in) and the 234/f quarter-wave vertical, in feet, inches and fractions or in metres

• Quarter wave in coax, using the velocity factor of the cable you select

POWER AND LEVELS

• dBm to watts, dBW and volts at your impedance, and back (30 dBm is 1 W; 50 W is 46.99 dBm; -60 dBm is 0.0002236 V at 50 Ω)

• Ratios to dB and dB to ratios: a ratio of 2 is 3.01 dB in power and 6.02 dB in voltage

VSWR

• Type a VSWR or a reflection coefficient, or a return loss in positive dB as your analyzer shows it (14 dB is 1.50:1); a negative S11 reading works too

• Return loss, reflection coefficient, mismatch loss, and the power reflected and delivered to the load in percent (VSWR 1.5: return loss 13.98 dB, mismatch loss 0.18 dB, 4 % reflected)

• From wattmeter readings: √(reflected ÷ forward) is the reflection coefficient

LINK BUDGET

• Free-space path loss from frequency and distance (2.4 GHz over 10 km: 120.05 dB), with the first Fresnel zone radius at the midpoint and 60 % of it (17.67 m and 10.60 m), plus the earth bulge to clear as well (1.47 m at k = 4/3)

• Receive level from transmit power, antenna gains (dBi, also shown in dBd) and losses (30 dBm, 15 dBi at both ends, 2 dB of loss at each end: -64.05 dBm) and the margin against receiver sensitivity (20.95 dB at -85 dBm)

• Miles or kilometres

COAX

• Seven cable types: RG-58, RG-8X, RG-213, RG-6, a low-loss 400 class, and ½ in and ⅞ in hardline, with typical loss per 100 ft (or 100 m), velocity factor and the line's electrical length in wavelengths and degrees at your frequency

• HF through microwave, as far as each cable's published figures go: RG-58 from 1 to 5800 MHz, hardline from 0.5 MHz, the low-loss 400 class from 30 MHz

• Total loss for the cable length you enter, from typical published values (see the cable's datasheet), ready to drop into the link budget as feedline loss

SOUND AND DELAY

• Delay for a distance at the speed of sound for the air temperature (100 ft at 68 °F: 88.8 ms; 34.3 m at 20 °C: 99.9 ms)

• The speed of sound, and the level drop between two distances by the inverse square law

• Wavelength, quarter wave and period for an audio frequency (1000 Hz: 1 ft 1 1/2 in, or 0.3432 m)

• Add sound levels in dB (90 dB and 90 dB: 93.01 dB; 80 dB more: 93.22 dB)

WORKS THE WAY YOU DO

• Feet, inches and fractions with miles and °F, or metres with kilometres and °C

• A results strip shows every solved value at once

• 10 memories, a tape of your calculations, reference tables (coax loss, VSWR conversions, dBm to watts, speed of sound) and a key guide

• Export a job strip: the tape with inputs, stamped and ready to attach to a lift plan, sign-off or take-off, as text or PDF

FREE TO TRY, THEN UNLOCK ONCE

Free to try: every feature for 7 days. Then unlock Pro once — no subscription, no ads, works offline.

PRIVATE BY DESIGN

Works offline, no account, no data collected.

How it's calculated: the formulas and tables behind every result, at https://wrightcalc.app/gainwright/

Questions or feedback: [email protected]

FOR PLANNING ONLY. Cable losses are typical values: check the cable's datasheet. RF exposure and licensing rules apply where you transmit. The developer accepts no liability for loss, damage or injury arising from use.