FM bug using salvaged SMD parts

If you’re a soldering ninja this FM transmitter bug is for you. It’s quite similar to the one we looked at yesterday, but this uses 100% salvaged parts. Two phones donated components; a Nokia 3210 for its voltage-controlled oscillator and a Nokia 1611 for the rest of the parts. The bad news is that mobile technology like cellphones use some of the smallest surface mount packages known to man. That’s where the soldering skill come into play. The good news is that if you’ve been scavenging for discarded phones in order to reuse their LCD screens you already have these parts on hand.

[Thanks George]


  1. biozz says:

    is it just me or is this smd one bigger than the threw hole one? XD

  2. Spork says:

    Prepaid Nokia phones from AT&T have been $8-10 recently. I bought a few for the LCD’s.. might be fun to make an FM bug inside the phone case.

    Hah, it does seem that way, huh?

  3. M4CGYV3R says:

    This looks about the same size as the one yesterday – at least H x W wise. It is certainly a slimmer profile vertically.

    With some work you could probably get the thing down to the size of a dime instead of the larger CR2032 button cell size like this.

  4. RadBrad says:

    Nice work!


  5. Leif-KC8RWR says:

    1km range at 420-480Mhz?
    I wouldn’t do that w/o a license.

    If you are receivable at 1km with a TV card you are probably receivable considerably farther by a ham with a decent base antenna from 430-450Mhz or worse yet by Police/Fire/Military/etc which use the rest of that band.

  6. xorpunk says:

    People are getting competitive over who has more knowledge of PCB and FM modulation..sad

    Sam size PCB..SMD components..better modulation method in comparison. You can still lose some of the filter bus and put a capacitor for more stable power. less money more field operation.

  7. AbirdToldMe says:

    fm transmitter, does that mean i could use a normal fm radio to tune in? thx – radio newb

  8. Chajtek says:

    This one is nicer. But still huge. This microphone will surely identify it’s purpose. There are smd microphones on market with even have energy saving mode like this:

    What range can you get without antena or with a tiny one like on bluetooth?

  9. xorpunk says:

    @AbirdToldMe:no its 430Mhz, and it drops as power lessens. FM modulation can be used on any broadcast bandwidth, even microwave.

    This is one place a PIC is actually needed, for a DSP based light encryption. You can also settle for modulation obfuscation, but that is too easy to figure out.

    Something like a IR laser or inductor tap going over digital shortwave is as good as it gets unless you have access to a reliable satellite link via packet radio :p

    Ive seen a project that could filter human voice off metal plumbing in a building or window frames and broadcast it too.

  10. bilbao bob says:

    xorpunk, I like the cut of your jib.

    Easy enough to modulate a mic and pump out visible or IR light next to the window. We used the plumbing in a tall building to pump a 56k data link from floor to floor (five floors away) without much trouble. Waste pipes and water supply were grounded, but not well enough.

    The world has come a very long way.

    It’s like Cellphones + Spectrum Analyzers.
    The 21st century – it’s magic, complete with rainbows, and it’s all elementary magic at that.

  11. strider_mt2k says:

    Super nice!
    -and definitely a plus using recycled parts.

    Chock full o’ win

  12. qwerty says:

    This sounds interesting though I’m not sure this is the right way of using that VCO, it should contain some circuitry to regulate the voltage that drives the VCO frequency.
    All searches for this part datasheets returned no useful results therefore I cannot tell what pin should be used for that purpose (pin 4 maybe).
    If anyone has a datasheet or a working link please post it somewhere, thanks.

  13. xorpunk says:

    @qwerty: not surprising as it all was pulled from cell phones. Especially the VCO.

    With this type of stuff, even the passive components, it usually takes probing and reverse engineering.

    @bilbao bob: If I was going RF itd definitely be digital over shortwave, because of the efficiency, and have a checksum and encryption protocol in a SMD DSP with PCB antenna.

    Id have it moduler with a wide-response mic, IR laser, and EMT configuration. Use firmware and software for cleaning up, and focus on battery life with a bus for a lipo cell.

  14. Tachikoma says:

    This is way cool. The 1km range is impressive as well. And I just happen to have and old Nokia phone lying around in pieces.

  15. bilbao bob says:

    Another cool invention that people long before me invented – well, who cares.

    In 1984, I thought that the wide-band burst bug was a unique invention. You record at low quality for days or weeks – when there’s actually something to hear – and then spit it out at huge data rates with time stamps – equivalent to wifi at 50Mbs – in a single burst, which is repeated later just in case.

    Sadly, german uboats had prior art.

    Later, I thought I had again done something special – use a vox switch to record when something could be heard, buffer the data, and just keep up a quiet little low bandwidth stream of encrypted data that could be turned back into speech… running all the time. If there was no data to decode, you just sent random data until something new popped up. It doesn’t take much to bury the signal into the background noise.

    Sadly, and inevitably, there was french prior art, and it turned out to be a common technique of the ELF submarine crowd, including american subs.

    Technology has moved on, and now there are serial interface low power ram chips far advanced over our little 8 MB storage. And 8 pin processors that can do a/d, d/a, compression and power management with time to spare.

    “It’s so easy an arduino user could do it!”

    If you want to see these techniques in action, complete with remote api built into the hardware, just look at any smart phone built after 2009.
    It’s nothing short of amazing! :)

  16. uzerzero says:

    Amazing… after I build a couple of these, I can start my own private detective agency in Miami so I can get back into the CIA and beat Michael Westen to the punch.

  17. bilbao bob says:

    I can see it now, uzerzero posts two ads:

    “Wanted: Wise-cracking overweight black detective with two weeks until retirement and overly attractive tattooed female crop-duster pilot.
    Mission: Replace Fidel Castro with Dick Cheney’s half-cousin Raoul and turn Cuba into the west coast version of Kauai, but with better hotels and casinos.”

    “Wanted: stock footage of a seaplane, three trained dobermans and several high mileage late model police cars with current collision insurance.”

  18. Tachikoma says:

    bilbao bob, you come across as one of the old folks who’s seen the world go to hell and back.

  19. Circuitgram says:

    We can try this circuit as a simple FM bug

  20. Nice.
    But it will be very hard to solder this circuit.

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