A tiny FM transmitter
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Tiny FM Transmitter v1 Gerber.zipV.1 Gerber Files
x-zip-compressed - 11.90 kB - 02/18/2018 at 11:04
Portable Network Graphics (PNG) - 33.86 kB - 02/18/2018 at 10:45
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.
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The potentiometer acts as a voltage divider to change the voltage coming into the VCO and adjust the frequency.
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 :)
I'll get around to it in the coming days, currently in maths test panic mode
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?)
Probably, will check when I get home
Edit: Yep, its the MAX2606EUT+T
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?
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.
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...
That´s very interesting !! It´s very clean with this low part count..:! Did you made some range estimations ?
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.
Hey that´s awesome !! Very neat spy bug.. :-))
is it open source? Would love to see the schematics :)
I'll get around to adding them
Nice project! Is there a Git Hub repo for the project?
Not at the moment, should probably set one up though.
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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.