How does the Iridium 9704 compare with Starlink and OneWeb?
Series Building with the Iridium 9704 Part 10 of 10
In short
Different jobs: Starlink is broadband; the 9704 is small, frugal, rain-tolerant messaging.
Starlink and OneWeb are broadband internet services: fast, but with large, power-hungry terminals on high frequencies that suffer in heavy rain. The Iridium 9704 is a messaging service: slow, but on L-band, steady in bad weather, with a small, frugal module suited to portable and battery-powered devices.
| Item | Iridium Certus 9704 (IMT) | Starlink Mini |
|---|---|---|
| Band | L-band, 1616–1626.5 MHz | Ku-band: receive 10.7–12.7 GHz, transmit 14.0–14.5 GHz |
| Effect of heavy rain, cloud and fog | Low frequency, little effect | High frequency, signal attenuates in heavy rain |
| Size and weight | Module 31.5 × 42.0 × 3.8 mm, 12 g | Antenna 298.5 × 259 × 38.5 mm, 1.10 kg |
| Power | About 6 mAh to download and 12 mAh to upload 100 KB (N3D estimate) | 25–40 W average |
| Antenna | Small antenna, no pointing | Phased array, software-assisted manual orienting, 110° field of view |
| Speed | About 4.4 kbps down, 4.0 kbps up (N3D measured) | Broadband internet |
| Best for | Messages, sensor data, photos, voice clips; battery-powered and portable | Internet, video, high data volumes; stable power |
OneWeb's user terminals also use Ku-band and measure about 30–65 cm.
Why L-band holds up in bad weather
Rain, cloud and fog attenuate radio signals more at higher frequencies; the ITU's rain and cloud attenuation models exist to calculate exactly this. Ku- and Ka-band signals fade noticeably in heavy rain; Iridium's 1.6 GHz is affected very little. In Taiwan, typhoons, the plum-rain season and afternoon thunderstorms are exactly when messages most need to get through.
Why it suits portable devices
- Small: the 9704 module is smaller than a business card and weighs 12 g, so it fits handhelds, phone clips and small sensors.
- Frugal: a 100 KB round trip uses about 37–41 mAh including idle time. The same 3,000 mAh / 3.7 V battery (about 11 Wh) would run a Starlink Mini at 25–40 W for only about 17–27 minutes.
- No pointing: the antenna only needs to see the sky, even on the move.
How to choose
- Internet, video or live high-volume data, with vehicle or mains power: a broadband service such as Starlink.
- On batteries, small, and must get through in bad weather: the Iridium 9704.
- Both: broadband day to day, Iridium as backup; when broadband is down, position, status and emergency messages still get through.
Calculation and sources
- Battery energy: 3,000 mAh × 3.7 V ≈ 11.1 Wh.
- Starlink Mini run time: 11.1 Wh ÷ 40 W ≈ 0.28 h (about 17 minutes); 11.1 Wh ÷ 25 W ≈ 0.44 h (about 27 minutes). Conversion losses not included.
- 9704 energy per 100 KB round trip, about 37–41 mAh including idle and the board: N3D rooftop tests (9 and 25 October 2026).
- 9704 size and weight: Iridium, "Iridium Certus 9704 Module". Iridium band 1616–1626.5 MHz: Iridium product specifications.
- Starlink Mini size, weight, average power, orienting and field of view: Starlink, "Mini Specifications" sheet.
- Starlink user terminal bands: US FCC authorisation for SpaceX user terminals. OneWeb user terminal bands and size: OneWeb presentation published by the ITU.
- Rain and cloud attenuation: ITU-R P.838, "Specific attenuation model for rain for use in prediction methods"; ITU-R P.840, "Attenuation due to clouds and fog".
Iridium is so slow. Why use it?
Many applications need messages that always get through, batteries that last and hardware that fits, not speed. A scene photo arriving in a few minutes is enough for monitoring and rescue.
Can the two be used together?
Yes. Use broadband for high data volumes day to day and the Iridium 9704 as backup; when broadband is down, position, status and emergency messages still get through.
All parts in this series
From developer kit to certified product: what an Iridium 9704 product needs, the limits of the developer kit, why certification matters, how to choose hardware, where it fits, and measured timing and power. Ten parts, in order, each readable on its own.
- What do you need to build an Iridium 9704 product?
- What problems does IMT CC actually solve?
- What are the limits of the Iridium 9704 Launch Pad?
- Why do 9704 products need certification, and what does it cover?
- Who is the RockBLOCK 9704 for?
- Launch Pad, N-9704, RockBLOCK 9704 or your own design: which should you choose?
- Where can the IMT 9704 be used? Mountain rescue, maritime and monitoring
- How should power be designed for the 9704?
- Why can an IMT message take several minutes?
- How does the Iridium 9704 compare with Starlink and OneWeb?
Related hardware
Related services
Updated 2026-10-27
N3D supplies satellite communication for alpine and industrial use. See services