Radio Hijacking / Batteries to 12v cigarette jack

[neolemacheon]

I'm working on a radio hijacking project (basicly you broadcast over the frequency that someone is listening to their radio on) and have come up with the Griffin iTrip Auto Universal + ( http://www.griffintechnology.com/products/itripautouniversalplus ) upto 30ft range (and can be extended with a little hardware hacking) the only downside is that it requires a 12 volt powersource (the cigarette jack) while the advantages are that it can be used with anything with a 1/8" jack (laptops, mp3 players) to replace ambient (and usually bad) radio wherever it is found.

I was thinking 8 AA batteries wired in series and then attached to the positive/negative points on the car plug or two 9 volt batteries with some sort of stepdown.

So, the question is:

Does anyone know where a guide or vidcast for converting batteries to a 12 volt cigarette jack is? (or just tips or advice, as if I don't find anything decent I'll probably just go into the project feet first)

(I'm guesing it would be too like the USB power supply ep http://revision3.com/systm/solo/ to warrant another appearance, but it would make a nice episode)

Thanks for any help, tips, advice or links in advance

[tehboris]

Might want to use D batteries, will last longer.

[dosbomber]

I'd be highly surprised if the device you list in your post will have the power output to "hijack" an existing broadcast station. Generally you have to live deep in the sticks with very few local radio stations (read: a big gap between existing frequencies) to get these to work. In bigger cities it's almost impossible to find a frequency that isn't being used or "leaked" into by a big station. It's not the range that's the problem, your device will act like someone trying to whisper in your ear and be louder than someone across the room with a rock concert speaker at full blast.

Give it a try, though. Good luck with the project.

[melta]

Im getting in a similar project, I used this FM transmitter article (http://hem.passagen.se/communication/ipod.html) for inspiration as i have the exact same transmitter. It's a very good and detailed article i think. And you would be surprised how effective it is!

[kd7lxl]

Fun project. When I lived in the dorms we got our janitor's boombox with one of these. He thought our porn audio was the DJ of his favorite station having sex in the studio. "Oh, he's so fired" "That dude won't have a job tomorrow, I can't believe it." Just for the lulz.

Get something like this that will hook 8 1.5v AAs in series (12v total): http://www.radioshack.com/sm-8-aa-battery-holder--pi-2062251.html

Alternatively, try harder: open the transmitter. It may just convert to 5v or something interally. Look for a voltage regulator chip and find the output with a volt meter. In this case you may want to build a 5v battery pack, or whatever is necessary, and power the circuit directly. If you screw up you'll likely have to buy a new transmitter.