How to Build a Homemade Long Range Radio Transmitter

   

Homemade Long Range Radio Transmitter – a great diy project

They might seem unrelated but the FM radio is essentially the forebear of the cellular networks that we’re currently using to communicate with each other. Most people turn on their radios to listen to music but wouldn’t it be nice to actually transmit your own music for other people to hear?

Super small radio transmitter diy project

Super small radio transmitter diy project

A project by Angelo Casimiro of the TechBuilder Youtube channel shows how easy it is to build a portable homemade long range radio transmitter with just a few components and tools that anyone could buy online (or at a local RadioShack). What’s great about Angelo’s DIY FM Radio transmitter is that almost anybody can make it regardless of technical know-how or age.

Schematic for a radio transmitter bug diy project

Schematic for a radio transmitter bug diy project

Parts and Tools

To start building Angelo’s homemade long range radio transmitter, you will have to gather/purchase the required components first (all of which are available online or in any electronics shop). Start first with acquiring a piece of copper clad PCB/Perfboard, an Electret Microphone, solid gauge #18 wire, and a ¼” bolt. For transistors, capacitors, and resistors, refer to the list below:

Capacitors

4pF Ceramic Capacitor15pF or 40pF Trimmer Capacitor10nF Ceramic Capacitor2 x 100nF Ceramic Capacitor

Resistors

1M Ohm ¼ Resistor3 x 10K Ohm ¼ Resistor1K Ohm ¼ Resistor100 Ohm ¼ Resistor100K Ohm ¼ Resistor

Transistors

2 x 2N3904 General NPN Transistor

Additionally, a soldering iron, a mini drill, hot glue gun, and a pair of pliers are needed to place these parts in place later on. For its power source, this homemade long range radio transmitter will be running off a 9-volt battery that can be bought in any convenience store.

Soldering the homemade pc board

Soldering the homemade pc board

PCB Fabrication and Soldering

The most crucial part of this whole process is fabricating the PCB. Prior to this though, print the layout for the PCB as well as the schematics (both are found in the instructables.com link provide in the video’s description). In the video, Angelo followed the presensitized PCB fabrication process although the toner transfer method will also work. After developing the PCB through this method, it was then placed in a plastic tray and etched with Ferric Chloride. The next step involves pouring acetone on the PCB and using a swab to remove its photo-positive layer. Following this step, Angelo then soldered the circuits, electret microphone according to the schematics diagram. To make the coil, he took the solid gauge wire and coiled it around the bolt 7-8 times (this was also soldered to the PCB). Finally, the last two items to be soldered/attached to the PCB were the battery and the antenna. The glue gun was then used to hold everything together.

Testing the Transmitter

In order to tune the homemade long range transmitter, the screw on the trimmer capacitor needs to be turned until your FM radio (you can also use a cellphone with an FM radio) produces loud feedback. You can then turn on your laptop/desktop’s speaker and position the transmitter so that the Electret microphone is facing it directly. Your FM radio should now pick up on whatever sound/music is coming from the speaker.

Applications

This homemade radio transmitter can broadcast up to a ¼ mile out which means that it’s ideal for use at home. People can use this to monitor their rooms, listen in on the noises their babies are making, as well as for listening to various sounds in nature. Of course it’s also possible to connect this with your mp3 player so that you can broadcast your playlist to anyone lucky enough to be in your immediate vicinity. Take note though that there are some countries that consider radio transmitters like this as illegal though so if you’re planning to build one, make sure that you check with your local/national laws first.