Transistor fm radio receiver circuit series#

The layout I used for the protoboard build: ConstructionĪlthough I didn’t build on a breadboard, this is what it could look like (stray capacitance may make this difficult): I don’t have any 2N5109’s, so I’ve simply used S9014 with only a 270MHz gain bandwidth product,Īlthough of the stock I have on hand, an S9018 (800 MHz) might have been a better choice. The circuits that reportedly work well are using either the BF494 or BF199 NPN transistors -īoth obsolete products and marketed as an “RF Transistors” with gain bandwidth product over 1100 MHz.Ī good substitution is perhaps 2N5109 with a 1200MHz gain bandwidth product. One other variation in my circuit was the choice of transistor. I added 60cm of random wire, with a 10pF coupling capacitor. I tried both combinations, with the final “good” circuit using the parallel arrangement (maybe it would work just as well going to ground, but I haven’t testing it).Įven though I have relatively strong FM broadcast signals in my area, I found an antenna indispensible. Some have it in parallel going to the positive rail.

Transistor fm radio receiver circuit series#

One difference between various designs is the positioning of the variable capacitor - some have it in series with the coil and going to ground, That corresponds to the performance I’m seeing - able to pick up all stations up to around 97.4 MHz very clearly. (that’s a bit on the low side for the braodcast FM range, but I’ll have a shot at shifting the range That theoretically gives me a tuning range of

Given the variable capacitor I’m using ranges from about 5pF to 22pF, I was getting with the coil I wound according to original instructions. I finally started to get good results with a 4 turn, 17mm diameter coil of 0.4mm enamelled wire.Īccording to my LCR meter, this measures at around 0.55µH - much higher than the ~0.1µH then one is probably tuning on a mess of harmonics/mirror images, not the actual signal.If the signal is weak and there is no selectivity: The sweet spot I settled on was 5V supply and R1=22kΩ Try lower voltage or increasing R1… this circuit works well down to around 3V.I had no success at all with the 9V battery and R1=10kΩ shown on many schematics.R1 drops the battery voltage to tank circuit.If there is no signal at all, the operating voltage may be swamping the tank circuit: weak signal lost in the noise (if any signal at all)Īfter much experimentation, the lessons learned.My first builds following the schematic exactly were spectacularly unsuccessful: The basic design I’m using here is from Mikroelektronika’sģ.15.2 The Simplest FM Receiver with Audio Amplifier. The best version I’ve seen is perhaps the build by Lechoslowianin, “Proste radio FM jak zrobić”: Great Scott built a version but didn’t get great results: One of the first I found that demonstrated decent results was “How to make FM Radio receiver at home” by RJ Imagination:

There are a number of YouTube videos of builds, demonstrating a wide degree of success. Many variations of this ciruit are available around the web, often with the addition of an LM386 amplifier stage, Of Mikroelektronika’s excellent online book “Radio Receivers, from crystal set to stereo”. The most basic version of a simple direct conversion FM radio is covered in selecting an appropriate operating voltage.appropriately sizing the coil in the resonant tank circuit.) I’m finally able to get this show on the road! Well, I had another shot at it today and finally (with the help of an I could never get a decent enough result to call the project “done”, so it always went back on the shelf I’ve actually had “build a simple FM receiver” in my WIP bucket for years (literally). Taming a very simple direct conversion FM receiver.