# Mercury HF Modem — Email and files over HF radio

> Email and files over HF radio (iPhone/iPad app by Rhizomatica Communications.)

- Source: https://appshunter.io/ios/app/mercury-hf-modem/id6822504870 (this page in markdown: same URL + `.md`)
- Developer: [Rhizomatica Communications](https://appshunter.io/developer/6822504872)
- Category: Utilities, Productivity
- Price: Free
- Age rating: 4+
- Requires: iOS 17.0 · 26 MB
- Languages: American English
- Released: 2026-10-26
- Data updated: 2026-10-27

## What is Mercury HF Modem?

Mercury is a software modem for sending email, files and messages over HF radio, the kind of link you have when there is no internet, no phone network and no power grid worth speaking of.

Connect your phone or tablet to a single-sideband transceiver through an audio interface, and Mercury turns the radio into a data link: it handles the waveform, the error correction, the retransmissions and the speed, and gives your application an ordinary TCP connection. It speaks the VARA TNC protocol, so Winlink clients such as Pat, and chat programs, can use it.

• Adaptive speed, from a robust 32-tone MFSK mode that works below the noise up to 16-QAM on a good channel.
• Files arrive intact or you are told they did not.
• Broadcast mode for one-to-many traffic.
• The same modem as Mercury on Linux, Windows and macOS: they talk to each other.

Mercury is free software (GPL-3.0) from the HERMES project of Rhizomatica. It needs an amateur-radio licence to transmit.

## Is Mercury HF Modem safe?

Not enough ratings yet to assess Mercury HF Modem.

## Is Mercury HF Modem legit?

Mercury HF Modem has limited verification signals. The AppsHunter Legitimacy Score for Mercury HF Modem is 50 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 1 release)

### 1.9.21 — 2026-10-26

First release on the App Store. Since 1.9.20: a session whose link drops below the control mode mid-transfer now reaches the robust MFSK floor in about two minutes instead of stalling (Winlink/Pat sessions stuck at FF>).

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-27.*