# Rattlegram — SMS via audio!

> Audio-based SMS transmission using COFDM technology. (iPhone/iPad app by aicodix GmbH.)

- Source: https://appshunter.io/ios/app/rattlegram/id1664526096 (this page in markdown: same URL + `.md`)
- Developer: [aicodix GmbH](https://appshunter.io/developer/1664526098)
- Category: Social Networking
- Price: Free
- Rating: 4.50/5 from 23 App Store ratings · 10 written reviews indexed
- Age rating: 4+
- Requires: iOS 17.6 · 1 MB
- Languages: American English
- Released: 2023-11-20
- Data updated: 2026-07-21
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/rattlegram/id1664526096/reviews.md

## What is Rattlegram?

COFDMTV is based on COFDM (coded orthogonal frequency-division multiplexing) technology:
- 160 ms long OFDM symbols
- 6.25 Hz per sub-carrier
- 1/8 guard interval
- differentially encoded PSK (phase-shift keying) modulation
- systematic polar codes for forward error correction

Currently Modes 14, 15 and 16 are supported:
Using either SPC(2048, 1392), SPC(2048, 1056) or SPC(2048, 712) with CRC32C aided SCL decoding and differential QPSK modulation for the payload.
Only a bandwidth of 1600 Hz is needed and the transmission of either 85, 128 or 170 bytes take about one second with the leading noise and fancy header disabled.

## Key features

- COFDM technology
- Audio-based SMS
- 160 ms OFDM symbols
- Differential PSK modulation
- Forward error correction
- Low bandwidth requirement

## Recent user reviews (10 of 10)

All indexed reviews: https://appshunter.io/ios/app/rattlegram/id1664526096/reviews.md

### 5/5 — Works!

*2026-03-15*

perfect, simple

### 5/5 — Texting via HT’s

*2026-03-06*

Allows texting via HT’s when off grid. Easy to operate as well.

### 5/5 — Great SMS App

*2025-01-27*

Excellent App. Was able to obtain App for iPad, iPhone, and Android Tablet. All communicated to each other perfectly and easily thru air as well as thru Baofeng UV-5R on VHF/UHF and G-90 on several SW bands. USB is touchy and tuning must be careful, but impossible.

I notice Android version slightly different than iOS version. Found no version for Mac. PC version somewhat difficult to install and requires Android to Windows plugin.

Perhaps greatest App I’ve ran across recently. Thanks!

73s, Tom, ex-WA0DJP

### 5/5 — Favorite radio messaging app

*2024-12-31*

Love this app, I use it with a digirig lite and it works perfect like that. I would also like to see KISS TNC support if possible!

### 5/5 — Me encanta

*2024-05-27*

Me he comprado unos cables de audio y conecto los walkis a dos teléfonos para mandar los SMS y me encanta como funciona es una pasada lo bien que descodifica el mensaje que mandas

**Developer response:** ¡Gracias por tu reseña de 5 estrellas! Nos alegra mucho saber que te encanta cómo Rattlegram descodifica tus mensajes. Agradecemos mucho tus comentarios. ¡Disfruta usando la app!

### 5/5 — Great program

*2024-04-05*

This work great. I am a HAM operator and can it also talk to FLDIGI or FLMSG? It is in PSK which is a great mode. Can’t wait to what else it can do. Thanks

**Developer response:** Thanks so much for the great review! We're glad you're finding Rattlegram useful.

While Rattlegram utilizes PSK modulation within its OFDM-based system, it's currently designed specifically for audio coupling and text-over-audio functionality.

We made a conscious decision to keep the app streamlined and efficient, so for now, it won't directly interface with modes like FLDIGI or FLMSG.

However, we appreciate your interest in expanding Rattlegram's capabilities. We're always looking for ways to improve the app, so your feedback is valuable. If there's a way to integrate functionalities that align with our core audio-based messaging, we'll definitely consider it for future development.

In the meantime, we hope you continue to enjoy using Rattlegram for clear and reliable text communication!

### 5/5 — Great idea

*2024-04-05*

I downloaded for my iPhone.  At the bottom it says unable to create decoder.  How can I fix?

**Developer response:** Thanks for letting us know about the "unable to create decoder" error on your iPhone.

To diagnose the issue, we need some information about the app's current settings.  If you can, please update to app version 1.8 (if you haven't already) and then navigate to the "Danger Zone" menu.

Within "Danger Zone," look for options displaying the current recording and playback sample rates.  Once you have those numbers, please let us know!  With this information, we can help determine the next steps.

Thanks for your patience and assistance!

### 1/5 — Downloaded app, functions missing.

*2024-03-10*

Please advise. It appears as the IOS version has text creation and call sign disabled, however mike is still enabled on install. Please advise and I will test again and re-rate. Thanks

**Developer response:** Hi there, thanks for letting us know about the text/call sign issue on iOS. To help us fix it, could you send screenshots or a short video of what you're seeing? We appreciate your feedback!

### 5/5 — Amazing

*2024-03-08*

Very cool app not too sure how too delete messages but amazing

**Developer response:** Access the "Danger Zone" menu, and you'll find the "Delete Messages" option there. This allows you to clear your message history.

### 4/5 — I would give it 5 stars but…

*2024-01-26*

Really nice application that allows the transmission of text via two way radio.  Only reason I don’t give it 5 stars is that you don’t or I haven’t figured out yet, how to delete previous messages.  I would like to start a new session without seeing the history of past transmissions.

**Developer response:** Access the "Danger Zone" menu, and you'll find the "Delete Messages" option there. This allows you to clear your message history and start a new session without viewing past transmissions.

## Frequently asked questions about Rattlegram

### What is Rattlegram's primary function?

Rattlegram's primary function is to transmit SMS messages using audio signals, leveraging COFDM technology for efficient data transfer.

### What technology does Rattlegram use for SMS transmission?

Rattlegram utilizes COFDM (coded orthogonal frequency-division multiplexing) technology, which involves specific OFDM symbol lengths, sub-carrier frequencies, and modulation techniques.

### Does Rattlegram support different transmission modes?

Yes, Rattlegram currently supports Modes 14, 15, and 16, each with different configurations for systematic polar codes and CRC32C aided SCL decoding.

### What is the bandwidth requirement for Rattlegram?

Rattlegram requires a bandwidth of only 1600 Hz, making it efficient for transmitting data with minimal spectral usage.

### How fast can Rattlegram transmit data?

With the leading noise and fancy header disabled, Rattlegram can transmit 85, 128, or 170 bytes in approximately one second.

### What devices is Rattlegram compatible with?

Rattlegram is compatible with iPhones and iPads.

### What is the age rating for Rattlegram?

Rattlegram has an age rating of 4+, making it suitable for a wide range of users.

### Does Rattlegram have ads?

No, Rattlegram does not contain advertisements.

## Version history (last 4 releases)

### 1.10 — 2026-01-04

- improved navigation in settings
- updated libs and tools

### 1.9 — 2025-04-22

updated libs and tools

### 1.8 — 2024-04-05

* Improved robustness
* Improved signal encoding
* Prevent sleep while app is running
* Added delay for Parrot Mode
* Added debouncing for Parrot Mode
* Added new options to the Danger Zone:
- Toggle to favor Bluetooth audio if available
- Toggle to output audio to default speaker
- Print audio sample rates
- Button to restart audio engine if stuck

### 1.6 — 2023-11-20

No release notes.

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## Related topics

[rattlegram](https://appshunter.io/ios/topics/rattlegram) · [sstv decoder](https://appshunter.io/ios/topics/sstv-decoder)

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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 2026-07-21.*