Woulve's Blog – Blog

Turning a Raspberry Pi into an FM Radio Transmitter

Wed, 04 Mar 2026 15:24:00 +0100

The Problem

I bought a radio alarm clock for my bedroom. The goal was simple: get my phone out of there. Less doom-scrolling before bed, no “just one more video” at 1 AM, and an actual separation between rest and that attention-sucking rectangle we all carry around.

The plan worked, mostly. Except I live in a bit of a ditch, and FM reception here is garbage.

The Solution

I had a Raspberry Pi Zero 2W collecting dust. While looking for something to do with it, I stumbled upon PiFmRds, a project that turns the Pi into an FM transmitter. No extra hardware required, just a ~20cm wire connected to GPIO 4 as an antenna.

I was skeptical. Surely you can’t just… broadcast FM from a bare Pi? Turns out you can. The Pi generates the FM signal by abusing its clock generator to output a frequency in the FM band. It’s a clever hack that shouldn’t work as well as it does.

The Project

I wrapped PiFmRds into a more complete solution: a systemd service that streams internet radio and broadcasts it over FM, with automatic reconnection when streams drop.

The pipeline is simple:

curl fetches an internet radio stream
sox converts it to mono WAV at 44.1kHz
pi_fm_rds broadcasts the audio on your chosen FM frequency

Configuration lives in /etc/fm-radio/config where you set the stream URL, broadcast frequency, and RDS metadata (station name and radio text that shows up on compatible receivers).

Web UI

I also built a web interface so I can manage everything from my phone. It lets you:

Change the stream URL and FM frequency
Set RDS station name and radio text
Save station presets for quick switching
Start, stop, and restart the service
View live logs

Range

This surprised me the most. I expected maybe a few meters, enough to reach the bedroom.

Driving away from my house one day, I tuned into the frequency out of curiosity. I could still hear it clearly 200 meters down the road. The 20cm antenna wire apparently does more than I gave it credit for.

Note

FM transmission is regulated in most countries. Keep the power low and don’t interfere with legitimate broadcasts. This is meant for personal, short-range use.

The Setup

git clone https://github.com/woulve/pifmwebradio.git
cd pifm-webradio
sudo ./install.sh

The web UI at http://<pi-ip>:8080 handles all configuration, or edit /etc/fm-radio/config directly if you prefer.

Final Thoughts

There’s something satisfying about repurposing old hardware. The Pi Zero 2W went from a drawer to being genuinely useful.

I tried various stations, but ended up settling on a 1920s-style webradio stream. The vinyl crackling, the bandwidth limitations of the era, and the tinny speakers of the cheap alarm clock just pair well together. I sometimes let it play as I fall asleep.

Sometimes the best projects are the ones that solve a small, specific problem you didn’t think had a solution.

Free your Kindle!

Sun, 16 Nov 2025 17:01:00 +0100

Why Bother?

Amazon recently decided to prevent users from directly downloading the ebooks they’ve paid for.
This isn’t just a small inconvenience. It’s a reminder of how fragile “digital ownership” is when it’s wrapped in restrictive cloud ecosystems and licensing terms.

If you care about actual ownership, offline access, long-term preservation, or simply being able to load your own books onto your own device, this shift is painful. Yes, there are still ways to strip DRM, but these methods are against Amazon’s TOS and noticeably more tedious than before. And even if you manage to free your files, sending them to the Kindle via Send-to-Kindle works only when it feels like it.

I often get books from sources other than Amazon (don’t let Jeff bezos read this), so unlocking the full functionality of my Kindle has been on my to-do list for a long while.

Unfortunately, the newer Kindle OS versions weren’t vulnerable to the older WinterBreak exploit, which only supported up to version 5.18.0.2.

That changed recently with the release of AdBreak, a jailbreak that works all the way up to OS version 5.18.5.0.1.

Note

You need a Kindle with ads enabled. If you previously disabled them, you can re-enable them by switching the account region. This is explained here

How the Jailbreak Works

The AdBreak process is straightforward and takes around fifteen minutes. In short, you let the Kindle download ads, copy those ads to a computer, and then run a script that exploits a use-after-free vulnerability in the Kindle’s browser sandbox. This enables code execution, which then triggers the jailbreak via a specially crafted image.

The Steps in Brief

Fill your Kindle’s storage with dummy files to prevent automatic updates.
Wait for the device to download its ad bundle.
Copy the ads folder to your computer.
Unzip AdBreak and run the exploit script, which leverages a use-after-free vulnerability described here
Install the required hotfix to ensure the jailbreak persists after reboot.

After that, you’re jailbroken.

Disabling Updates and Installing Apps

Once the jailbreak is in place, you’ll want to disable OTA updates and install some essential tools.

Installing MRPI and KUAL

Extract MRPI (MobileRead Package Installer) and KUAL (Kindle Unified Application Launcher) to your Kindle, then run the command ;log mrpi in the Kindle search bar.

Inside KUAL, use the Rename OTA binaries option to disable over-the-air updates permanently.

Adding Apps with KindleForge

One of the easiest ways to install additional software is by using KindleForge, a GUI-based app store for Kindle homebrew packages.

Some of my personal favorites:

Ad Remover: Removes ad banners
kTerm: A terminal emulator
Gambatte-K2: A Game Boy emulator (yes, you can genuinely play Game Boy games on a Kindle)

The Real Star: KOReader

KOReader is the main reason I wanted to jailbreak my Kindle in the first place. It supports a wide variety of formats, provides much more control over typography, and integrates beautifully with Calibre, OPDS catalogs, SSH syncing, and more.

I keep all my ebooks in Calibre on my home server, and with KOReader I can browse the entire library from anywhere and download books directly to my Kindle, essentially recreating the Kindle Store experience but for my own collection.

Tip

The KOReader user guide is extensive and worth a look if you’re diving in: https://koreader.rocks/user_guide/

Final Thoughts

This whole process made me dust off my Kindle and use it far more than before. It also brought back the nostalgia of jailbreaking iPods and rooting early Android phones. It was a reminder of the joy that comes with reclaiming control over your devices.

My Self-Hosted Home Lab

Sun, 26 Oct 2025 12:00:00 +0100

Why Local-First?

This is the current trend in smart home and cloud services: everything requires connectivity and a terrible app that exists primarily to monetize you. Your light bulb doesn’t need to know your sleep schedule. Your photos don’t need to train someone else’s AI. Your documents don’t belong on a server you don’t control.

So I built my own infrastructure. Everything runs on Unraid, stays on my network, and works without internet. No accounts, no subscriptions, no data leaving my home. The trade-off is maintenance overhead, but the control is worth it.

The Hardware

The server started as an old gaming PC:

Component	Spec
CPU	Intel i7-6700
GPU	Nvidia GTX 1070 (for Plex transcoding and local AI)
RAM	32GB DDR4
Storage	3x 4TB HDD + 2x SSD cache

Not cutting edge, but more than enough for a home server. The GPU handles hardware transcoding in Plex and runs LLM models in Ollama.

Backups

Weekly backups of all app data run via Borgitory, a container that wraps Borg backup with a clean UI. Backups sync to a Hetzner storage bucket for offsite redundancy. If the server dies, I can restore everything.

Services Overview

Home Automation

Home Assistant, Zigbee2MQTT

Media

Plex, Navidrome, Calibre, Audiobookshelf

Files & Sync

Syncthing, Nextcloud, Paperless

Local AI

Ollama, Open WebUI

Home Automation

Home Assistant

Home Assistant integrates all smart devices and handles automation logic. From turning on lights at sunset to adjusting thermostats based on occupancy, it automates a lot of useful tasks. The dashboard is fully customizable, and the community has tons of integrations for different devices.

Tip

To get nice looking isometric background images, take a picture of a room and use ChatGPT to generate them with a prompt like: “Generate an isometric image of this room”.

Zigbee2MQTT

Zigbee2MQTT bridges Zigbee devices to MQTT, enabling local control of smart lights, sensors, and switches without any cloud dependency. I use the SONOFF Zigbee 3.0 USB Dongle Plus which works great with currently 40+ devices.

Media

Service	Purpose
Plex	Movies and TV shows
Navidrome	Music streaming (Subsonic-compatible)
Audiobookshelf	Audiobook and podcast management
Calibre	Ebook library management

Plex handles video, Navidrome streams my music collection to any Subsonic client, Audiobookshelf manages audiobooks and podcasts with progress tracking, and Calibre organizes my ebook library.

Photos & Documents

Service	Purpose
Immich	Photo backup and browsing (Google Photos replacement)
Paperless-ngx	Document management with OCR
Nextcloud	Calendar and contacts sync

Immich backs up photos from my phone and provides a polished experience. Paperless-ngx scans, OCRs, and organizes documents. Nextcloud syncs calendars and contacts via CalDAV/CardDAV.

File Sync

Syncthing keeps files synchronized across all my devices without any central server. It’s peer-to-peer, encrypted, and works very well to sync my documents and media between my laptop, desktop, and server.

Local AI

Service	Purpose
Ollama	Local LLM inference
Open WebUI	ChatGPT-like interface for Ollama

Running LLMs locally means conversations stay private. Ollama makes it easy to run models like Llama, Mistral, or Phi.

Knowledge

Kiwix serves a local mirror of Wikipedia. Works offline, loads instantly, and provides access to human knowledge even when the internet is down.

Gaming

A Minecraft server for friends and family, routed through playit.gg to make it accessible without exposing my home IP or opening ports.

External Access

For services that need to be publicly accessible, I use Cloudflare Tunnels. No port forwarding, no exposed IP, and Cloudflare handles SSL. The tunnel container connects outbound to Cloudflare, which proxies traffic back to my services.