Pirate Radio
This was a fun project I made with the goal of living like an awesome pirate. For years I've had a dream of building a huge pirate ship and embarking on the high seas in search of treasure. And every ship's captain needs a sweet sound system.
In this project, I learned how to convert electricity into radio waves and scored experience with electronics and programming a Raspberry Pi. By putting an antenna on one of the pins and flashing both audio files and radio software on its SD card, the little computer was able to transmit FM signals.
I purchased a Raspberry Pi 4, heat shrink tubing, jumper wire, and a micro SD card. It was my first time seeing a micro SD in person, and it was super cute - literally the size of a fingernail.
Flashing Raspberry Pi OS onto the micro SD card was notably straightforward. This is the only time I've used a Linux product and not had Stack Overflow open.
I powered the Raspberry Pi on, and connected to it via SSH. I used the Fing app on my phone to find its IP address, and logged in using that.
Lo and behold, it worked! I was on air! The pictures don't have sound but surely you can imagine the excitement coming from the success. Constructing a simple radio transmitter taught me a lot about radio antennas, FCC law, and Raspberry Pi OS, which were topics I knew nothing about before.
The radio transmitter described in this blog was constructed and operated in full compliance with FCC regulations, specifically §15.239. All emissions were limited to the 88-108 MHz band, with field strength measured at 3 meters not exceeding 250 microvolts, as required by law. Frequencies and emission standards outside of this range were strictly avoided to ensure legal operation.
In this project, I learned how to convert electricity into radio waves and scored experience with electronics and programming a Raspberry Pi. By putting an antenna on one of the pins and flashing both audio files and radio software on its SD card, the little computer was able to transmit FM signals.
I purchased a Raspberry Pi 4, heat shrink tubing, jumper wire, and a micro SD card. It was my first time seeing a micro SD in person, and it was super cute - literally the size of a fingernail.
Flashing Raspberry Pi OS onto the micro SD card was notably straightforward. This is the only time I've used a Linux product and not had Stack Overflow open.
I powered the Raspberry Pi on, and connected to it via SSH. I used the Fing app on my phone to find its IP address, and logged in using that.
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| A useful radio |
From there, I experimented with three different FM transmitter programs. The first two didn’t produce any signal at all, and the third gave me either static or a piercing high-pitched tone. Naturally, the first two got scrapped, and I focused on debugging the one that at least made some noise.
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| No output frequency Cool text art though |
Getting it to work meant a lot of trial and error with both hardware and software. I started by adding a jumper wire to the default transmitter pin (GPIO 7), which doubled as a makeshift antenna. Even this simple addition boosted the signal strength noticeably.
I added aluminum foil and heat shrink tubing to the jumper wire to increase its output power. The foil is tightly flattened and aligned vertically, which radiated signals better than the jumper wire alone due to reduced impedance. The tubing was placed at the base of the antenna, insulating it from adjacent pins.
Signal interference was still an issue, though. After some testing, I updated the code to transmit from GPIO 40 instead of GPIO 7. Since GPIO 40 sits on the far corner of the board, it isolated the antenna from noisy components, giving a much cleaner signal.
I added aluminum foil and heat shrink tubing to the jumper wire to increase its output power. The foil is tightly flattened and aligned vertically, which radiated signals better than the jumper wire alone due to reduced impedance. The tubing was placed at the base of the antenna, insulating it from adjacent pins.
The radio transmitter described in this blog was constructed and operated in full compliance with FCC regulations, specifically §15.239. All emissions were limited to the 88-108 MHz band, with field strength measured at 3 meters not exceeding 250 microvolts, as required by law. Frequencies and emission standards outside of this range were strictly avoided to ensure legal operation.