Getting your APRS packet digipeated through a satellite is one of those things that sounds complicated but is surprisingly achievable with a basic VHF setup. Your packet goes up, bounces off a satellite 400–500 km above you, and lands on APRS.fi — received by iGates across a 4,000 km footprint.
The key rule: no WIDE paths
The single most important thing to understand before transmitting via satellite: do not use terrestrial APRS paths.
A packet with WIDE1-1,WIDE2-1 relayed through the ISS digipeater would flood every iGate and digipeater within the satellite’s entire footprint simultaneously. This is a known source of congestion and will get you noticed for the wrong reasons.
The correct path for satellite APRS is simply:
ARISSThat’s the alias the ISS onboard TNC responds to. It digipeats your packet once and stops there.
Active satellites
ISS — the workhorse
The most reliable option. The ISS runs an onboard TNC (currently identified as RS0ISS) on 145.825 MHz simplex — same frequency up and down.
| Uplink | 145.825 MHz FM |
| Downlink | 145.825 MHz FM |
| Mode | 1200 baud AFSK (Bell 202) |
| Path | ARISS |
| Doppler | ±3.5 kHz — small enough to ignore for 1200 baud packet |
A pass lasts about 10 minutes. Beacon every 2 minutes and you get 4–5 attempts per pass. Because the frequency is 2m, Doppler is minimal and you don’t need to retune — just set 145.825 and leave it.
Verify your packets arrived at aprs.fi after the pass. If you see your callsign there, it worked.
IO-86 (LAPAN-A2 / LAPAN-ORARI)
A cross-band digipeater: you transmit on 2m, it retransmits on 70cm.
| Uplink | 145.825 MHz FM |
| Downlink | 435.880 MHz FM |
| Mode | 1200 baud AFSK |
| Path | ARISS |
The uplink is the same as ISS, so no changes there. The downlink is on 70cm where Doppler matters — about ±10 kHz over a full pass:
| Phase | Downlink frequency |
|---|---|
| AOS | 435.890 MHz |
| TCA (closest approach) | 435.880 MHz |
| LOS | 435.870 MHz |
Status is intermittent — worth checking amsat.org/satellite-status before planning a session.
TEVEL-2 to 7
A constellation of six Israeli cubesats launched in 2022, all in the same orbital plane. They carry FM voice repeaters and APRS digipeaters. You work whichever one is overhead.
| Uplink | 145.970 MHz FM |
| Downlink | 436.400 MHz FM |
| Mode | 1200 baud AFSK |
| Path | ARISS |
Same Doppler situation as IO-86 on the downlink. Load all six TLE sets in Gpredict so you can see which bird has the best pass.
Dire Wolf configuration
If you’re using Dire Wolf with an AIOC or similar soundcard interface, add a second beacon definition for satellite use. Keep it separate from your terrestrial beacon — different path, different comment, and you only want it firing during a pass.
# Satellite APRS beacon — activate manually during a pass
# Comment out the terrestrial PBEACON when using this
PBEACON delay=1 every=2 overlay=S symbol="/-" \
lat=52.52N long=13.40E \
comment="APRS via satellite | DL7EDU" \
via=ARISSKey differences from a terrestrial config:
via=ARISS— notWIDE1-1every=2— beacon every 2 minutes; a pass is ~10 minutes so you get 4–5 shotsdelay=1— give the satellite a minute to rise before the first beacon
Pass prediction and tracking
Gpredict is the tool for this. Set your location, load the TLE sets for ISS, IO-86, and the TEVEL birds, and it will show you upcoming passes with elevation, direction, and Doppler curves.
For quick pass times without installing anything: heavens-above.com works well from the browser.
Aim for passes above 25–30° elevation — you’ll have a longer window in the satellite’s footprint and better link margin.
Antenna
A rubber duck works, but a simple 2m vertical omni (even a slim jim or J-pole) noticeably improves results. For the 70cm downlink on IO-86 and TEVEL, a handheld dual-band yagi makes a real difference — point it at the satellite and rotate as it moves across the sky.
References
- AMSAT satellite status page
- ARISS news and ISS repeater status
- Gpredict
- Heavens Above pass predictor
- ISS Fan Club — live ISS APRS
73 de DL7EDU