A plain-text calculator that speaks RF natively: complex numbers and units aren't bolted on, they're how the language works — which is exactly what impedance, SWR and link-budget math need.
Eighteen calculators
Every one of them is a plain .dply file — open it, read the formulas, change the numbers for your own station. The core math computes for free; Pro adds a fillable form and, where it fits, a chart.
Power ratios and voltage ratios to dB and back, watts to dBm and back, and a rough dBm-to-S-meter reference — the conversions you reach for constantly.
Great-circle distance and beam heading between two Maidenhead locators, short path and long path. Decodes the locator with ord, no lookup table needed.
A measured voltage and current as complex phasors: impedance via division, magnitude and phase angle, a series impedance added on, and real/reactive power split out with conj.
How much of your power reaches the antenna: matched line loss, the extra loss your SWR costs, and the watts left at the feed point.
How long to cut the wire: half-wave dipole and quarter-wave vertical length from your design frequency, in metres and feet, with the end-effect factor spelled out.
Electrical length of a run of coax in degrees, how far off the nearest quarter-wave you are, and the impedance of a quarter-wave matching transformer.
Match two resistive impedances with one coil and one capacitor: network Q, both reactances, component values, and the bandwidth that comes with them.
What impedance does an arbitrary length of feedline actually present at its input, given a complex load? The exact line equation with complex numbers, plus the reflection coefficient and VSWR at the load.
Design a matched Pi- or T-pad for a wanted attenuation and line impedance — both topologies' resistor values side by side, plus a power-dissipation check.
SWR across the band for a resonant antenna — band-edge values, the exact 2:1 bandwidth, and the curve as a chart.
Path loss from distance and frequency, then a full link budget — EIRP, received power and your margin above the receiver's noise floor. Built for satellite and EME work.
Line-of-sight isn't enough — how much of the first Fresnel zone does an obstacle actually eat into, and does it still clear the usual 60% planning threshold?
What noise figure does your whole receive chain have once feedline loss and later stages are factored in — and which stage actually dominates it?
From noise figure and bandwidth to the minimum discernible signal, then predicted third-order intermod products and spurious-free dynamic range from a stated OIP3.
Same peak power, very different heat: DC-to-RF efficiency, then average dissipation across SSB, CW and a 100%-duty digital mode on the same amplifier.
Will the heatsink keep the junction temperature safe? Series thermal resistance from junction to ambient, plus the reverse calculation for sizing one.
Will this battery get you through the activation? Capacity, RX/TX current draw and your transmit duty cycle turn into hours and minutes of runtime.
A .dplybundle with a reusable Morse library: encode text to Morse and decode it back, letters and digits and punctuation, both directions from one table. Opens as a form, too.
Why not just an SWR app
Most ham calculators do one thing and forget it the moment you close them. A draftply document is plain text: your build notes, your formulas and your numbers live together, stay editable, and can be handed to another op or saved next to your station log.
What's built in
Free where the numbers are. Pro for the front panel.