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    #41
    Re: FM Jammer project

    Most modern day tuners are PLL locked, even with an analog tuning dial they lock onto frequency very well. It's only the older AFC type tuners that will drift slightly.

    So if the guy will retune to anywhere along 88-108 that means it will rule out a lot of fixed and small band frequency transmitters.

    IIRC my bluetooth transmitter was like $25 or something, don't remember. Getting a kit that frequency lock for that much would be hard unless you're using a RPi0 as a transmitter...

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      #42
      Re: FM Jammer project

      The Pi is not exactly cheap if I'm going to use it for this sole purpose...I'll probably still get one because it's got a lot of potential to be turned into something else once I get tired of my pirate radio. He actually got the point and turned it off for today !
      Wattevah...

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        #43
        Re: FM Jammer project

        Originally posted by Dannyx View Post
        I wonder how much the price point plays a role...I'm guessing not too much, because they all have to comply with certain limitations, so the price may only add features and not overall power, so I guess for this purpose cheaper is better...
        Pretty much - at least when it comes to the eBay/Amazon "cigarette plug" ones. I got mine for... $5 shipped to me? Or was it $8? - I can't remember, but either way it was below $10. A big computer chain here (MicroCenter) was selling similar ones in their (brick-n-mortar) store for $13. They all work, but build quality is pretty crap, of course. And their range sucks, as I mentioned. If you get one, just plan to open it and add an antenna. And while at it, also check all wires and solder joints. Mine came barely working, with one of its power wires hanging on just by a few threads. I still need to do more mods to it, too. Main problem(s) I have with it right now is that it has no input capacitor before its internal 7805 regulator. So every time I bump the transmitter a bit harder and if it looses power for even a pico-second, it resets. A big input cap could really help that. Not to mention I probably should put a large external resistor before the 7805 to help dissipate some of the heat so that the 7805 doesn't have to as much. The thing only draws about 0.1 Amps, but multiply that by the 8.odd Volts it dropps, and you have almost 1W of power dissipated on a 7805 regulator with a tiny PCB heatsink. It gets quite hot after some use. The resistor will not only help with the power dissipation, but putting a big electrolytic cap after will make a nice LC low-pass filter that should clear a lot of the noisy power from the engine.

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