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Project Notes

#281 FM/ThreeStageTransmitter

Build an “ugly-style in a can” version of dazaro3’s 3-stage FM transmitter circuit.



I got such good results with LEAP#280 BreadboardTransmitter that I decided to make something more permanent than a breadboard.

Since I have some Altoids tins collecting dust for just such an occasion, I’m doing this “ugly-style in a can”.


In the initial circuit I have 33pF C4 in the tank circuit. This produced a transmission frequency of 97.4MHz, which happens to be quite busy in my area. After adding another 33pF C9 in parallel (effectively 66pF), I moved the transmission to a much clearer 79.8MHz.

Output power is very good - easily transmits around my house. The microphone is very sensitive, and the pre-amp is fairly high gain. Loud sounds close to the microphone can be quite distorted/clipped.


Layout is derived from LEAP#280 BreadboardTransmitter design:


A strip of copper PCB is the positive rail anchoring the circuit:


Lots of space in the can for battery compartment, switch/LED/microphone attachments and the circuit itself. The case provides the ground plane:





The Real Deal

So after hacking away on dazaro3’s designs I thought I should get a “real” one as a way of saying thanks.

It just turned up, and works great. Happily I see the performance is very similar to the builds I’ve done already. Here are some pictures:




Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.