Developed by the team at aicodix GmbH, Rattlegram brings together advanced digital signal processing and clever open-source software to let your phone do something truly unique: send and receive messages through sound, much like how old-school modems used to—but way more modern and mobile-friendly.

What Is Rattlegram?

Rattlegram is an innovative app that turns your smartphone into a two-way audio communicator for text. It uses a method called COFDMTV (Coded Orthogonal Frequency Division Multiplexing with Time Variation) to encode text into sound. Your phone’s microphone and speaker become the only tools needed to “hear” or “speak” messages.

You can try it out yourself on both iOS and Android:

• Download for iOS
• Download for Android

And if you’re curious about how it works in action, check out the short demo and community videos here:

How Does It Work?

Rattlegram relies on several open-source projects developed by aicodix:

• OFDM Modem
  Core engine for encoding and decoding messages:
  github.com/aicodix/modem
• Polar List Decoder
  Used for reliable error correction:
  github.com/aicodix/code
• DSP Library
  Handles the nitty-gritty of digital signal processing:
  github.com/aicodix/dsp

All of these are released under the extremely permissive BSD Zero Clause License, meaning the code is not only free to use—it’s free to build upon with zero restrictions.

Respecting Your Privacy

Because Rattlegram listens for sound-based messages, it does require access to your phone’s microphone. But here’s the good news: your privacy is fully respected.

• The app does not record or store any audio.
• It uses a temporary buffer in memory just long enough to decode the signal.
• Only the final decoded text message is saved to your device’s storage.

You’re in full control, and everything happens transparently and securely on your device.

Why Try Rattlegram?

Whether you’re a tech hobbyist, amateur radio enthusiast, or just curious about sound-based communication, Rattlegram is worth exploring. It’s open, experimental, and surprisingly fun. You can even use it offline—in a noisy room, at a hackathon, or to communicate without the internet.

So go ahead—send your first message over sound and experience digital communication in an entirely new way.

Visit aicodix.com for more information or to dive deeper into the technology behind Rattlegram.

Let your messages rattle through the air—with Rattlegram.

The post Rattlegram – The Sound of Digital Messaging appeared on Hamradio.my - Amateur Radio, Tech Insights and Product Reviews by 9M2PJU.

In the ever-evolving world of amateur radio, digital voice modes have revolutionized how we communicate. Among the various software options available, DroidStar stands out as a versatile and powerful solution for digital voice communication. This comprehensive guide will walk you through everything you need to know about DroidStar, from its features to installation and configuration.

What is DroidStar?

DroidStar is an open-source application that connects to various digital voice systems including:

• M17 (with open-source Codec2 vocoder)
• Fusion (YSF/FCS, supporting both DN and VW modes)
• DMR (Digital Mobile Radio)
• P25 (Project 25)
• NXDN (Next Generation Digital Narrowband)
• D-STAR (REF/XRF/DCS reflectors)
• AllStar nodes (as an IAX2 client or using Web Transceiver mode)

Originally developed as two separate projects (DudeStar using Qt Widgets UI and DroidStar using Qt Quick UI), they have now been merged into a single entity under the DroidStar name.

Key Features

Cross-Platform Compatibility

Built with the Qt C++ library, DroidStar runs on multiple platforms:

• Linux
• Windows
• macOS
• Android
• iOS (without USB device support)
• Other POSIX platforms with Qt availability

Hardware Support

DroidStar is compatible with:

• AMBE USB devices (ThumbDV, DVstick 30, DVSI, etc.)
• MMDVM modems for hotspot functionality
• MMDVM_HS (hotspot) modems

MMDVM Support

DroidStar can function as:

• A hotspot/repeater when connecting to a digital mode reflector/DMR server with an MMDVM device
• A stand-alone transceiver when using ‘MMDVM Direct’ mode (currently M17 only)

Optional Features

• Flite Text-to-Speech: For testing without speaking (requires building with Flite TTS support)
• Software vocoder plugin API: For loading vocoder software (proper licensing required)

Installing DroidStar on Linux Using Flatpak

Flatpak makes it easy to install DroidStar on any Linux distribution. Here’s how:

Step 1: Install Flatpak (If Not Already Installed)

For Debian/Ubuntu-based distributions:

sudo apt update && sudo apt install flatpak -y

For Fedora:

sudo dnf install flatpak -y

For Arch Linux:

sudo pacman -S flatpak

Enable Flathub repository:

flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

Step 2: Install DroidStar

Search for DroidStar:

flatpak search droidstar

You should see something like:

Name             Description                   Application ID                    Version          Branch        Remotes
DroidStar        A digital voice client        io.github.nostar.DroidStar        1.0.1-git        stable        flathub

Install DroidStar using:

flatpak install droidstar

When prompted with “Use this ref?”, type Y and press Enter.

Launch DroidStar with:

flatpak run io.github.nostar.DroidStar

Step 3: USB Device Permissions (Linux Users)

Linux users with USB AMBE and/or MMDVM dongles need to:

1. Add your user to the ‘dialout’ group
2. Disable the ModemManager service: sudo systemctl disable ModemManager.service
3. Reboot your system

Configuration Guide

Basic Setup

1. Enter Your Callsign: A valid amateur radio license is required
2. Choose Digital Mode: Select from DMR, D-STAR, YSF, NXDN, P25, or M17
3. Select Host/Module: Choose the desired reflector or server
4. Configure Mode-Specific Settings:
   • For DMR: Enter your DMR ID, latitude/longitude, location, and description
   • For D-STAR: Configure MYCALL, URCALL, RPTR1, and RPTR2 fields
   • For AllStar: Set up IAX client parameters or Web Transceiver details

Installing the Vocoder Plugin

DroidStar supports software vocoder plugins through its API. To install a vocoder:

Method 1: URL Download (Works on All Platforms)

1. Go to Settings tab
2. Enter the vocoder URL in the “Vocoder URL” field
3. Click “Download vocoder”

Method 2: Manual Installation (Linux/macOS/Windows)

1. Download the appropriate vocoder plugin matching your platform and architecture
2. Place the plugin in the system settings file location:
   • Linux: ~/.config/dudetronics/
   • Name format: vocoder_plugin.platform.arch
   • Example: vocoder_plugin.linux.x86_64

Note: The platform and architecture for your device are shown on the About tab. Remember that any vocoder plugin should be properly licensed by you if copyright patents apply.

Using DroidStar

For DMR Mode

1. Enter your DMR ID
2. Input the talkgroup ID number (e.g., 91 for Brandmeister Worldwide)
3. For DMR+ hosts, create your options string and check “Send DMR+ options on connect”

For D-STAR Mode

Enter the correct values for MYCALL, URCALL, RPTR1, and RPTR2 before transmitting.

For AllStar

DroidStar supports two methods for AllStar connectivity:

IAX Client Mode

1. Define IAX nodes on the Hosts tab
2. Select the node when IAX mode is chosen from the Main tab
3. Send DTMF commands like *3node, *1node, *70 in the IAX DTMF box

Web Transceiver Mode

1. Add a line in the Host tab with format: IAX 12345 wt 4569 allstar-public allstar
2. Add your ASL web portal password to “ASL password” under settings

Final Thoughts

DroidStar is a powerful tool for amateur radio enthusiasts looking to explore digital voice modes. Its cross-platform compatibility and support for various digital protocols make it a versatile option for both beginners and experienced operators.

While this software is provided as-is without official support, it benefits from the work of many open-source projects including MMDVMHost, MMDVM_CM, mvoice, and others. The vibrant amateur radio community continues to improve and expand DroidStar’s capabilities.

Whether you’re experimenting with digital modes or using it for emergency communications, DroidStar offers a flexible and accessible platform for digital voice communication.

Visit:

https://github.com/nostar/DroidStar

https://github.com/rohithzmoi/Droidstar-DMR

http://kapihan.net/connect/resources/files/droidstar-vocoders.php

The post DroidStar: The Ultimate Digital Voice Communication Tool for Amateur Radio appeared on Hamradio.my - Amateur Radio, Tech Insights and Product Reviews by 9M2PJU.

For amateur radio enthusiasts, the APRS (Automatic Packet Reporting System) network has long been a cornerstone of digital communication. Now, with the introduction of the MAIL APRS Bot, messaging within the ham radio community has become even more streamlined and functional.

What is the MAIL APRS Bot?

The MAIL APRS Bot is a specialized service that enhances the messaging capabilities of the existing APRS network. It allows ham radio operators to send direct messages to other users, join group conversations, and manage their communications efficiently—all through simple text commands sent over APRS.

Key Features That Make Communication Easier

Direct Messaging

Reaching out to another operator has never been simpler. By typing @CALLSIGN followed by your message, you can send a direct communication to any other ham on the network. For example, typing @N0CALL Hey there! How's it going? will deliver your greeting straight to N0CALL’s inbox.

Message Management

Checking your messages is as easy as typing APRSM, which prompts the bot to fetch your latest communications. If your inbox gets too cluttered, simply type del to remove messages you haven’t acknowledged yet, keeping your communications organized.

Automated Message Retrieval

For operators who are frequently on the air, the bot offers an automatic message retrieval system. By including either APMAIL or ALLMSG in your comment beacon, you’ll receive incoming messages as they arrive, without having to manually check.

Group Communications

Perhaps the most exciting feature is the ability to create and participate in group conversations—something that traditional APRS messaging hasn’t supported well.

To join a discussion group, simply send join group_name. For instance, join bigfoot would add you to the “bigfoot” discussion group. When you want to leave, unjoin bigfoot removes you from the conversation.

Group messaging works similarly to direct messaging, but with a hash symbol: #bigfoot Let's organize the next meetup! would send your message to everyone in the bigfoot group.

Practical Applications for Ham Radio Operators

The MAIL APRS Bot transforms how amateur radio operators can coordinate activities:

• Emergency Response Teams can create temporary groups during incidents
• Special Event Operators can maintain group communication without clogging frequencies
• Club Members can share announcements without needing to reach every individual separately
• Field Day Participants can coordinate across operating positions

Important Notes About Using the Service

The system includes some thoughtful limitations to keep the APRS network running smoothly:

• Group messages remain available for 3 days before expiring
• Users automatically leave groups after 1 day of inactivity (reducing clutter)
• Individual messages are purged after 7 days
• Group messages are only visible to group members

Getting Started

To begin using the MAIL APRS Bot, you don’t need any special equipment beyond your existing APRS setup. The commands are sent through standard APRS messaging, making this service accessible to anyone already on the network.

For more detailed information, you can visit the official documentation at https://aprs.wiki/mail/.

Conclusion

The MAIL APRS Bot represents an exciting evolution in amateur radio digital communications. By adding group messaging capabilities and streamlining message management, it makes APRS more versatile and user-friendly while respecting the bandwidth limitations of the network.

Whether you’re coordinating emergency communications, organizing a ham radio club event, or simply chatting with fellow operators, the MAIL APRS Bot offers powerful new tools that bring modern messaging concepts to the traditional amateur radio experience.

Have you tried using the MAIL APRS Bot yet? What groups would you create for your local ham community?

The post MAIL APRS Bot: Revolutionizing Ham Radio Messaging appeared on Hamradio.my - Amateur Radio, Tech Insights and Product Reviews by 9M2PJU.