Doppler Shift
Frequency shift for a moving target — one-way or radar (two-way).
Your recent runs (stored only in your browser)
No calculations yet — results land here so you can compare runs.
The engineering
The radar factor of two: the wave gets compressed on the way out *and* on the way back. A 30 m/s car at 10 GHz returns 2 kHz of shift — audio-range, which is why early police radar literally listened.
Sign convention: closing targets shift up. LEO satellites swing ±10s of kHz through a pass, which is what your SDR's Doppler correction is chasing.
Where this math comes from
Christian Doppler proposed the effect in 1842 for starlight; Buys Ballot tested it in 1845 with trumpet players on a train, possibly the most charming experiment in physics. Radar engineers of WWII turned it from curiosity to weapon — moving-target indication separating aircraft from ground clutter by shift alone.
The same arithmetic tracks weather, baseballs, blood flow, and every satellite pass; it is the physics of relative motion writ in hertz.
- 1842Christian DopplerProposes the frequency shift of moving sources.
- 1845C.H.D. Buys BallotConfirms it with musicians on a moving train.
- 1943WWII radar teamsMoving-target indication — Doppler goes operational.
See the full timeline of the math behind every calculator →
Runs entirely in your browser — nothing you enter leaves this page. Your recent runs are stored only on your device.