#281 FM/ThreeStageTransmitter
Build an “ugly-style in a can” version of dazaro3’s 3-stage FM transmitter circuit.
Notes
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”.
Performance
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.
Construction
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:
