Amateur Radio Satellite Reception

~140 min7 Steps

Track LEO amateur satellites with Gpredict, receive FM and linear transponder signals, decode telemetry, and compensate for Doppler shift in real time.

Prerequisites
Gather these before starting the workshop
  • RTL-SDR dongle (v3 or Blog V4 recommended) or handheld 2m/70cm radio
  • Directional antenna: Arrow Antenna II, Elk 2m/440L5, or similar dual-band Yagi
  • Gpredict installed and configured with your location
  • SDR++ or GQRX for signal reception
  • Optional: Hamlib + rigctld for automatic Doppler correction
Step 1 of 714% complete
Amateur Satellite Overview: ISS, SO-50, AO-91
15 min
Step 1

Amateur satellites typically pass overhead in 5–10 minute windows, rising to maximum elevation and then dropping below the horizon. You have a limited time window to work each pass, so preparation is everything.

Amateur Radio satellites (ARSATs) are built and operated by radio amateurs worldwide under AMSAT coordination. Unlike commercial satellites, many are accessible with modest handheld equipment — even a $25 RTL-SDR can receive several of them.

ISS (International Space Station)

FM Voice Repeater / APRS

Up: 145.990 MHz (APRS) / 144.490 MHz (voice)

Down: 145.800 MHz (APRS) / 145.800 MHz (voice)

Most famous amateur asset in orbit. APRS digipeater is nearly always active. Voice repeater activated only during special events.

SO-50 (SaudiSat-1C)

FM Repeater

Up: 145.850 MHz (67.0 Hz CTCSS)

Down: 436.795 MHz

One of the most accessible FM satellites. Cross-band repeater: uplink on 2m, downlink on 70cm. Requires a tone to activate.

AO-91 (RadFxSat)

FM Repeater

Up: 435.250 MHz

Down: 145.960 MHz

Reverse of SO-50: uplink 70cm, downlink 2m. Often very busy during good passes. Strong downlink signal.

Orbit characteristics and why they matter

Low Earth Orbit (LEO)

All amateur satellites listed here are in LEO at 400–600 km altitude. This means very fast passes (about 17,000 km/h ground speed), high Doppler shift, and short contact windows. The advantage: strong signal — only ~3 dB free-space path loss compared to GEO satellites.

Pass geometry

A satellite rises at AOS (Acquisition of Signal), reaches maximum elevation (called MAX EL) mid-pass, then sets at LOS (Loss of Signal). Higher MAX EL = longer pass + stronger signal. Passes above 30° elevation are easiest for beginners.