What frequency does the ISS use for amateur radio?

The ISS amateur radio system operates on 145.800 MHz downlink and 145.990 MHz uplink for FM voice. The ISS also runs an APRS digipeater on 145.825 MHz and occasionally transmits SSTV images on 145.800 MHz. These frequencies are in the VHF 2-metre band and can be received with a handheld radio and a simple whip antenna.

How do I correct for Doppler shift when working amateur satellites?

LEO satellites move at approximately 7.5 km/s, causing frequency shifts of up to ±10 kHz on UHF and ±3.5 kHz on VHF. For FM satellites, your receiver bandwidth usually absorbs the shift. For SSB/CW linear transponders, the standard practice is to correct on the uplink side — adjust your transmit frequency to compensate, keeping the downlink frequency stable. This tool computes the corrected frequencies for you in real time.

What equipment do I need to work amateur radio satellites?

For FM satellites like SO-50, ISS, and TEVEL, a dual-band handheld radio (such as a Yaesu FT-65 or Baofeng UV-5R) with a simple directional antenna (Arrow II or Elk log-periodic) is sufficient. For SSB/CW satellites like FO-29 and QO-100, you need an all-mode transceiver, a directional antenna with azimuth/elevation tracking, and a way to correct for Doppler shift. A Yagi or helical antenna on a manual rotator works well for portable operation.

Which amateur satellites can I hear with a handheld radio?

FM repeater satellites are the easiest targets for handheld radios. Current active FM satellites include SO-50 (SaudiSat-1C), ISS cross-band repeater, PO-101 (DIWATA-2), and the TEVEL constellation. You can also receive CW beacons and telemetry from many CubeSats. A directional antenna significantly improves reception, but even a whip antenna can pick up the ISS.

What is a Maidenhead grid locator?

A Maidenhead grid locator (also called a QTH locator) is a coordinate system used by amateur radio operators to describe their location. It encodes latitude and longitude as a short alphanumeric string like IO91wm (central London). The first two letters identify a field (10° × 20°), the next two digits a square (1° × 2°), and the optional last two letters a subsquare. It is the standard way hams exchange locations for satellite contacts.

How long does an amateur satellite pass last?

Most LEO amateur satellites orbit at 400–800 km altitude, giving pass durations of 5–15 minutes depending on maximum elevation. A high-elevation pass (70–90°) can last up to 12–15 minutes, while a low pass near the horizon may only be 3–5 minutes. Higher-altitude satellites and the QO-100 geostationary transponder provide much longer or continuous access windows.

Can I add satellite passes to my calendar?

Yes — this tool provides one-click .ics calendar export for individual passes or a full week of amateur radio passes. Each calendar event includes the satellite name, uplink/downlink frequencies, mode, start and end times, maximum elevation, and compass direction. The .ics format works with Google Calendar, Apple Calendar, Outlook, and any standards-compliant calendar application.

What does OSCAR mean in amateur radio?

OSCAR stands for Orbiting Satellite Carrying Amateur Radio. The designation is assigned by AMSAT (the Radio Amateur Satellite Corporation) to satellites that carry amateur radio payloads. The first OSCAR satellite launched in 1961, just four years after Sputnik. Today, over 100 satellites have received OSCAR designations, and the numbering continues with each new amateur radio satellite.

Live Ham Sat Passes

Amateur Radio Satellite Passes

The web's only free pass predictor with live Doppler-corrected frequencies. Find upcoming passes for 80+ active OSCAR and CubeSat amateur payloads — FM repeaters, SSB/CW transponders, APRS digipeaters and SSTV — with uplink/downlink, mode, QTH locator, polar sky chart, and calendar export.

— active amateur satellites tracked

— FM Repeaters

— Linear Transponders

— Digipeaters

— Passes (24h)

↑↓ navigate · Enter select · Esc close

QTH

All Passes Radio passes visible at any time

Min El 10°

Set your location to see amateur radio satellite passes overhead. We'll calculate real-time Doppler corrections for your exact position.

A satellite pass is live now

◉ Live Pass — —

↑ Uplink — Tune Your Radio To

—

↓ Downlink — Listen On

—

Approaching (+freq) Overhead (0 shift) Receding (−freq)

Mode: — Elev: —° Az: —° Range: — km

Tip: For linear transponders, correct on the uplink — tune your transmit frequency as shown above. Keep the downlink frequency constant and let the receiver track it. For FM satellites, your radio's bandwidth absorbs the shift — no manual correction needed.

● Disconnected WebSerial API — connect your radio via USB

Automatically pushes Doppler-corrected frequencies to your radio in real time. Supports Yaesu CAT, Icom CI-V, and Kenwood TS-2000 protocols.

Radio Sky Chart

Polar projection — centre is zenith, edge is horizon. Dot colour shows Doppler state: blue = approaching, white = overhead, red = receding.

N S E W

Approaching (+Doppler)

Overhead (zero shift)

Receding (−Doppler)

Active Frequency Bands

Simultaneous Passes 0

First Satellite Contact Guide

1. Set Your Location

Enter your city or QTH grid square above. We'll calculate passes specific to your position.

2. Find an FM Pass

Filter by "FM Repeater" — look for passes with "Handheld OK" badge and >30° elevation. These are the easiest.

3. Set Your Radio

Program the uplink and downlink frequencies shown on the pass card. Set a CTCSS tone if shown (e.g. 67.0 Hz for SO-50).

4. Point & Listen

When the pass starts, point your antenna in the direction shown. Listen first — hear the repeater tail or other operators.

5. Make the QSO

Key up briefly: your callsign and grid square. Keep it short — the pass is shared. Congratulations on your first satellite contact!

Working Amateur Radio Satellites — Complete Guide

How Satellite Pass Predictions Work

Amateur radio satellite pass predictions use Two-Line Element sets (TLEs) to calculate exactly where each satellite will be at any future time. The SGP4 propagation algorithm models the satellite's position second by second, while Orbital Radar cross-references each NORAD catalogue entry against the SatNOGS transmitter database to identify which objects carry amateur radio payloads and what frequencies they operate on.

Unlike visual satellite passes, amateur radio passes do not require darkness or twilight — you can work a satellite pass in broad daylight, in rain, or through clouds. The only requirement is that the satellite is above your horizon (typically 10° elevation or higher for a usable signal).

Understanding Doppler Shift

LEO satellites orbit at approximately 7.5 km/s. This velocity causes the received frequency to shift — higher as the satellite approaches, lower as it recedes. The effect is more pronounced at higher frequencies: a 435 MHz downlink shifts by approximately ±10 kHz over a pass, while a 145 MHz signal shifts ±3.5 kHz. For FM satellites, your receiver's bandwidth (typically ±5 kHz) absorbs most of the shift. For SSB and CW operation on linear transponders, you must actively correct for Doppler or your signal will drift out of the passband.

The standard practice is to correct on the uplink (your transmit frequency) and leave the downlink constant. This means everyone monitoring the satellite's downlink hears a stable signal from you. Orbital Radar's Doppler gauge computes this correction in real time using the satellite's range-rate derived from SGP4 propagation.

Getting Started: Equipment Guide

FM Repeater Satellites

Dual-band handheld (VHF/UHF) with a simple directional antenna. Works with manual Doppler correction or none at all for FM. The easiest way to make your first satellite QSO.

Yaesu FT-65, Kenwood TH-D75, Baofeng UV-5R • Arrow II, Elk LP

SSB/CW Transponders

All-mode transceiver (IC-9700, FT-991A) with a directional antenna on a manual or automated rotator. Requires active Doppler correction — use this tool's live frequency readout.

Icom IC-9700, Yaesu FT-991A • Cross-Yagi, helical antenna

APRS & Digital

Any radio capable of 1200 baud AFSK on 145.825 MHz. Use Direwolf or an APRS-capable HT. The ISS digipeater is a popular entry point — your packet gets repeated from space.

Kenwood TH-D75, Mobilinkd TNC • Direwolf software TNC

Receive-Only / SWL

An RTL-SDR dongle (£25) and a simple VHF/UHF antenna can receive beacon telemetry, SSTV images, and voice from dozens of satellites. No licence required for receive-only.

RTL-SDR V4, Nooelec NESDR • Discone or turnstile antenna

Key Amateur Radio Satellites

As of 2026, there are approximately 80–120 active satellites carrying amateur radio transponders or beacons. The most popular targets include the ISS (cross-band FM repeater and APRS digipeater), SO-50 (SaudiSat-1C, one of the longest-running FM satellites), FO-29 (Fuji-OSCAR 29, an SSB/CW linear transponder approaching its 30th year), and the TEVEL constellation of FM CubeSats. The geostationary transponder QO-100 (Es'hail-2) provides continuous coverage for operators in its footprint across Europe, Africa and Asia.

Making a Contact (QSO)

Satellite QSOs are brief by necessity — a pass typically lasts 5–15 minutes and is shared by many operators. The standard exchange on FM satellites is callsign and grid square. On SSB/CW, you can exchange signal reports (RS/RST) as well. Keep transmissions short, use the minimum power necessary (5W is typically sufficient for LEO FM), and always listen before transmitting to avoid doubling.

For more orbital mechanics context, visit the Orbital Academy. To track specific satellites in 3D, use the live globe. Browse all tracked objects in the satellite directory or explore the full Space Library with 175+ reference pages covering everything in orbit.

Last updated: 3 May 2026