Ham Sat Tracker

What Is Doppler Shift — and Why Does It Matter?

Amateur satellites travel at roughly 7.5 km/s. As the satellite approaches your position, the received frequency is compressed slightly higher than the transmitted frequency. As it recedes, the frequency stretches lower. This is the Doppler effect — the same phenomenon that makes a passing train's horn change pitch.

Which Satellites Should You Start With?

If you're new to satellite operating, start with the FM voice repeater satellites. They work just like a terrestrial repeater — key up, speak, unkey — except the repeater is 500 km overhead and moving at 27,000 km/h. SO-50 (NORAD 27607) has been in orbit since 2002 and remains one of the most reliable FM satellites.

What Equipment Do You Need?

For FM satellites, the minimum working station is a dual-band radio capable of split operation (transmitting on one band while receiving on another simultaneously) and a handheld yagi antenna.

Do I Need a Licence?

Yes — transmitting through amateur satellites requires an amateur radio licence. In most countries, a Technician class licence (USA) or equivalent entry-level licence is sufficient to operate on the 2-metre and 70-cm frequencies used by FM satellites. You can receive satellite signals without a licence — and listening to passes is a great way to learn before you transmit.