Tiny FM transmitter

Description

This is a, well, tiny FM transmitter that can have various applications both *probably* legal (pirate radio, your own low-power radio station...) as well as the undoubtedly illegal (FM jammer, spy bug...). The choice is yours!

It can run on a voltage between 3 and 13 volts, draws 2-3 milliamps and has a theoretical output power of ~3 milliamps (although you could easily add an RF amplifier).

Files

Tiny FM Transmitter v1 Gerber.zip

V.1 Gerber Files

x-zip-compressed - 11.90 kB - 02/18/2018 at 11:04

Download

Schematic.png

V.1 Schematic

Portable Network Graphics (PNG) - 33.86 kB - 02/18/2018 at 10:45

Preview

Components

1 × MAX2606 Clock and Timer ICs / Clock Generation and Distribution

1 × AP2210 - 3.3v Power Management ICs / Linear Voltage Regulators and LDOs

1 × Electret microphone

1 × 390nH - 0805

1 × 2.2K ohm - 0805

Project Logs

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Teeny tiny...
James Pae • 02/19/2018 at 17:46 • 0 comments

I attempted to use a CR2032 with the circuit and, to be honest, i wasnt too sure if it would work. I suspected that something weird would happen when feeding only 3 volts to the 3.3 volt regulator or the vco being too sensitive, etc. However, none of those scenarios came to be true and it worked wonderfully. Although i suspect the output power has gone down, there were no issues and the frequency stayed rather stable.

View project log

Discussions

tomeks1972 wrote 02/28/2018 at 20:01

What frequency did you set? According to the datasheet for 390nH it should be about 103MHz, but I am curious what your effective frequency is. Interesting project by the way.

Are you sure? yes | no

James Pae wrote 03/01/2018 at 15:01

The potentiometer acts as a voltage divider to change the voltage coming into the VCO and adjust the frequency.

Are you sure? yes | no

hene193 wrote 02/21/2018 at 18:50

Could it be possible to get a simple parts list? Just would be easier to know what size of resistor I need to order and so on. (I mean the package size) Thank you so much :)

Are you sure? yes | no

James Pae wrote 02/21/2018 at 21:03

I'll get around to it in the coming days, currently in maths test panic mode

Edit: Done

Are you sure? yes | no

hene193 wrote 02/22/2018 at 20:58

Thanks! Do you happen to know what MAX2606 you use? Most likely MAX2606EUT+T since it's range is "70 MHz to 150 MHz" (I don't know if that matters?)

Are you sure? yes | no

James Pae wrote 02/23/2018 at 06:39

Probably, will check when I get home

Edit: Yep, its the MAX2606EUT+T

Are you sure? yes | no

matseng wrote 02/21/2018 at 09:39

I had a quick peek at the datasheet but didn't see any specs for the frequency deviations caused by varying the VCC. Did you measure it and determined that a vreg was necessary or did you use one just in case?

Are you sure? yes | no

James Pae wrote 02/21/2018 at 10:33

I kept it in just in case (since this was my first endeavour into RF/FM, didn't create the original schematic. I found a good one online, re-created it in easyEDA and studied how it works. But I made the pcb layout myself). However, i found out that it worked fine with a 3v coin cell. So, I'm working on a smaller version without the regulator or potentiometer.

Are you sure? yes | no

matseng wrote 02/21/2018 at 11:42

That's a good reason. I usually stick to the original schematics (or recipe when cooking) when I do something unfamiliar/for the first time. Then the next time I'm always modding the heck out of it. Better safe than sorry...

Are you sure? yes | no

TheotherMike wrote 02/19/2018 at 18:05

That´s very interesting !! It´s very clean with this low part count..:! Did you made some range estimations ?

Are you sure? yes | no

James Pae wrote 02/19/2018 at 20:47

it's a bit fiddly but with my mediocre radio and a random piece of wire as an antenna, I managed to get 40-50 meters. I'm also working on a smaller version without the regulator and potentiometer.

Are you sure? yes | no

TheotherMike wrote 02/19/2018 at 20:55

Hey that´s awesome !! Very neat spy bug.. :-))

Are you sure? yes | no

davedarko wrote 02/18/2018 at 07:48

is it open source? Would love to see the schematics :)

Are you sure? yes | no

James Pae wrote 02/18/2018 at 08:22

I'll get around to adding them

Edit: Added

Are you sure? yes | no

oshpark wrote 02/18/2018 at 01:27

Nice project! Is there a Git Hub repo for the project?

Are you sure? yes | no

James Pae wrote 02/18/2018 at 10:39

Not at the moment, should probably set one up though.

Are you sure? yes | no

Tiny FM transmitter

Description

Files

Tiny FM Transmitter v1 Gerber.zip

Schematic.png

Components

Project Logs

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Teeny tiny...

Discussions

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Tiny FM transmitter

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Description

Files

Tiny FM Transmitter v1 Gerber.zip

Schematic.png

Components

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