General
Is Ham Sat Tracker free?
Yes — completely free, with no account and nothing to unlock. Every feature is available to everyone: all satellites, 7-day lookahead, date selection, Doppler-corrected frequencies, sky view plots, pass alerts, the live sky map, and one-tap handoff to AntTrack.
The site is supported by a small number of ads and by operators who choose to buy me a coffee. Ads never appear in AntTrack.
I used to have AntTrack Pro (or beta access) — do I need to do anything?
No. Everything Pro used to include is now free for everyone, so there's nothing to activate or restore. Just keep using the tracker and AntTrack as before. Thank you for testing and supporting the project early on.
Do I need to create an account?
No. Ham Sat Tracker works without any account or login. Your location and preferences are saved locally in your browser.
Does it work on mobile?
Yes — it's designed primarily for phone use in the field. AntTrack's compass-based antenna pointing specifically requires a mobile device with a magnetometer (compass) and accelerometer (tilt sensor). Most modern smartphones have both.
Can I install it as an app?
Yes. Open the tracker itself (not the home page), then on Android tap Add to Home Screen from Chrome's menu, or on iOS tap Safari's Share button and choose Add to Home Screen. The icon opens straight into the tracker, which also works offline once it has been opened online.
Pass Predictions
How accurate are the predictions?
Pass times are accurate to within a few seconds when TLE data is fresh (less than a few days old). Accuracy degrades gradually with older TLEs — predictions with data more than 7 days old should be treated as approximate. The header shows the age of your current TLE data.
Why does the app show no passes?
A few common reasons:
- Minimum elevation is too high — try lowering the slider to 5° or 0°
- Time range is too short — some satellites have long gaps between passes from a given location. Try 24h or longer.
- Location is wrong — double-check your grid square or coordinates
- The satellite is genuinely inactive — some birds have periods of inactivity. Check AMSAT Satellite Status for current activity reports.
What does max elevation tell me?
Max elevation is the highest point the satellite reaches during the pass. Higher is generally better — a pass at 70° max elevation gives you much more time in the usable part of the sky than a 15° pass. For FM satellites, anything above 20° is usually workable. Below 10° is often blocked by obstructions or too brief to be useful.
Why do some passes start or end at odd azimuths?
The AOS azimuth is where the satellite crosses your minimum elevation threshold — not necessarily due North or South. Satellites cross the sky at all angles depending on their orbital inclination and your latitude. The skyview polar plot on each pass card shows the full track visually.
Can I see passes for a specific future date?
Yes. The date picker lets you select any future date and see all passes for that day's window. Useful for planning a portable activation days in advance.
Doppler and Frequencies
What are AOS, TCA, and LOS frequencies?
These are the uplink and downlink frequencies corrected for Doppler shift at three points in the pass:
- AOS (Acquisition of Signal) — as the satellite rises. It's approaching, so the downlink is slightly higher than nominal and the uplink slightly lower.
- TCA (Time of Closest Approach) — the peak of the pass. Doppler shift is near zero, so frequencies are closest to the nominal values.
- LOS (Loss of Signal) — as the satellite sets. The reverse of AOS — downlink drops below nominal, uplink rises.
For FM satellites, start at the AOS downlink frequency and tune it slowly downward throughout the pass. For SSB linear transponders, continuous tuning is more critical — keep your own signal in position on the transponder passband.
My radio doesn't have the exact frequency shown — what do I do?
Round to the nearest 5 kHz for FM satellites — this is close enough. For SSB work, tuning in 100 Hz steps is ideal. The frequencies shown are calculated values; in practice you'll be tuning by ear anyway.
Why do I need a CTCSS tone for SO-50?
SO-50 requires a 67 Hz PL (CTCSS) tone on the uplink to open the repeater's squelch. Without it the satellite won't hear you even if your signal is strong. Program 67 Hz into your radio before the pass. If the satellite seems unresponsive, try a brief transmission with 74.4 Hz — this activates the satellite's 10-minute on-timer if it has gone to sleep.
TLE Data
What are TLEs?
TLE stands for Two-Line Element set — a standardised format for describing a satellite's orbital parameters. The predictor uses TLE data to calculate where each satellite will be at any given time. TLEs are published by CelesTrak and updated regularly as satellites experience small orbital changes due to atmospheric drag and other forces.
How often should I update TLEs?
For casual use, once a week is fine. For critical portable planning or when a satellite has recently manoeuvred, update before each session. The app does this automatically each time you load it if you have internet access.
Will the app work without internet?
Yes. After you've opened the tracker once with a connection, your phone keeps a copy of it, so it opens and calculates passes even with no cell service at all. The latest orbital (TLE) data is saved on your device after each successful update. When you're offline the tracker uses that saved data and shows a banner telling you how old it is.
For best results, open the tracker and tap Update TLEs before leaving home. Predictions stay reliable for several days after an update.
A few things still need a connection: the live map and sky map (the map images come from the internet), the satellite status badges (you'll see the last ones saved), and of course fetching fresh TLEs. AntTrack works fully offline once it has been opened online.
Pass Alerts
How do pass alerts work?
Each pass card has a 🔔 Alert button. Tap it to arm a 5-minute countdown before AOS. When the timer fires, an amber banner appears at the top of the page and a three-tone chime plays. Tap the button again to cancel. Multiple passes can be armed simultaneously — each has its own independent timer. Alerts require the page to stay open in your browser.
The chime isn't playing on my phone — what's wrong?
Mobile browsers require a user interaction before allowing audio to play (browser autoplay policy). Since you tap the Alert button to arm it, that interaction should be sufficient. If the chime doesn't play on the first try, arm the alert and then tap any button elsewhere on the page before the timer fires — this confirms the audio context to the browser and resolves the issue.
AntTrack Antenna Pointing
What is AntTrack?
AntTrack is the antenna pointing tool built into Ham Sat Tracker. It uses your phone's compass and tilt sensor to show real-time azimuth and elevation guidance during a satellite pass — so you know exactly where to point your antenna.
Why is my compass reading wrong?
The most common cause is that the phone's compass needs calibration. Before opening AntTrack, wave your phone in a figure-8 pattern for a few seconds outdoors — this resets the magnetometer. Other causes:
- Being indoors — building materials, wiring, and metal structures significantly deflect the compass
- A magnetic phone case — remove it before operating
- Metal vehicles or structures nearby — step away by at least a few metres
- No GPS fix — without GPS the phone may use magnetic north rather than true north, which is about 12° off in Ottawa
On iPhone, AntTrack shows a CMPS ±N° indicator in the status bar. If it shows red (±20° or worse) the compass needs calibration before the pass. Close AntTrack, do the figure-8 gesture, and reopen.
How do I know if my compass is accurate enough?
On iPhone, watch the CMPS dot in AntTrack's status bar. Green (±10° or better) means the compass is reliable. Amber (±11–20°) is marginal. Red (±20° or worse) means the compass readings won't be useful — do a figure-8 calibration gesture before proceeding. If compass accuracy is poor when GPS first locks, AntTrack will show an amber warning banner automatically.
On Android this accuracy reading isn't available, so use the figure-8 gesture as standard practice before every session regardless.
What does the elevation calibration step do?
When you enter the tracking screen, AntTrack shows a live tilt reading in degrees. Point your antenna boom at the horizon (0° elevation) and watch the number — when it settles near 0° and the display turns green, tap Calibrate. This zeros the tilt sensor for your specific phone mounting position so elevation readings are accurate throughout the pass.
The live reading updates 10 times per second. Watch for it to stabilise before tapping — if the number is jumping around, hold the antenna steadier.
Can I use AntTrack without a directional antenna?
AntTrack is most useful with a directional antenna like a handheld yagi or Arrow antenna where pointing matters. With an omni antenna there's nothing to point, though the elevation indicator can still tell you when the satellite is high enough to be worth listening for.
Satellites
Why isn't [satellite] in the list?
The satellite list is curated to include only currently active birds with recent operating reports. Satellites that haven't been heard from reliably are removed to avoid showing passes for birds that aren't working. If you think a satellite should be added, — I check the AMSAT Satellite Status Page regularly to keep the list current.
The ISS repeater isn't active during the predicted passes — why?
The ISS ARISS repeater is not always on. It operates on a schedule determined by the crew and ARISS, and is sometimes off for extended periods. Ham Sat Tracker shows ISS passes based on orbital mechanics regardless of repeater status. Check ariss.org for current status before planning an ISS pass.
Why does AO-7 have special notes?
AO-7 is a special case — it's been in orbit since 1974 and its batteries failed long ago. It operates only when in sunlight (Mode B: 145.850 uplink, 29.4 MHz downlink). Passes in eclipse will produce no signal. The operating notes on the pass card flag this.
Still Have a Question?
If your question isn't answered here, . I read every message and update this FAQ based on common questions.
73 de VE3AKK