This calculator determines the **Doppler frequency shift** caused by the relative motion between a satellite and a ground station.

When the satellite is approaching, the observed frequency increases (upshift). When it's receding, the frequency decreases (downshift).

The Doppler shift is computed as: \[ \Delta f = f \cdot \frac{v}{c} \] Where:

• f = transmit or receive frequency (Hz)
• v = relative velocity (m/s), negative if approaching
• c = speed of light ≈ 299,792,458 m/s

Typical LEO satellite velocities are around ±7.5 km/s. For VHF/UHF comms, Doppler shift can be several kHz — significant enough to require compensation in real-time.