I found this and am wondering if it would work to jam a tv's reception. Its an ascii circuit diagram so it has to be viewed with a fixed width font.

Only a lowlife would jam TV reception. It is clearly illegal. If you do it for real, I hope they catch you and subject to severe criminal and civil penalties.

well i dont think it weould affect anything except the tv in the room your in. its just a prank.

Originally Posted by Papabravo

Only a lowlife would jam TV reception. It is clearly illegal. If you do it for real, I hope they catch you and subject to severe criminal and civil penalties.

That's a good one... Back in high school (25 or so years ago...), the basic TV jammer was a popular project. We spent a lot of time trying to make the smallest PCB. The output was well within legal limits, basically same room. Since cable and satelite TV pretty much dominates most households (not mine), doubt many people build these things anymore.

I think this circuit is garbage. Uses a 7404 off a 9 volt battery. There is no inductor, no antenna.

If you don't know what it would or would not affect, why give it a second thought. If your intent is to cause distress to a nearby TV watcher, then it does not matter what power level you are using or how effective the device is. It is still wrong. Even if you don't get caught, you can be certain of my opinion of your actions. Just so we are clear.

Do you know a better way to make one?

Originally Posted by HarveyH42

That's a good one... Back in high school (25 or so years ago...), the basic TV jammer was a popular project. We spent a lot of time trying to make the smallest PCB. The output was well within legal limits, basically same room. Since cable and satelite TV pretty much dominates most households (not mine), doubt many people build these things anymore.

I think this circuit is garbage. Uses a 7404 off a 9 volt battery. There is no inductor, no antenna.

Exactly which legal limits are you talking about for the creation of harmful interference, to use the FCC's term. How would you feel if your little prank stopped a pacemaker, or interfered with a public safety response. Little pranks often have unintended consequences. Think about it. Find another outlet for your energy and creativity.

Originally Posted by Papabravo

Exactly which legal limits are you talking about for the creation of harmful interference, to use the FCC's term. How would you feel if your little prank stopped a pacemaker, or interfered with a public safety response. Little pranks often have unintended consequences. Think about it. Find another outlet for your energy and creativity.

I will try not to kill anyone with my 9v battery and 7404 chip.

Just like how I try not to kill someone when I choose to drive drunk. What you think it might do is irrelevent to what it will actually do.

Originally Posted by dknguyen

Just like how I try not to kill someone when I choose to drive drunk. What you think it might do is irrelevent to what it will actually do.

Well I suppose it is lucky I have been sober for 15 years and have never made a TV jammer.

Yes it is, so why smear a spotless record?

The trasmitter's output was below 1/10th watt. So, pacemakers are that sensitive to low power transmitters? Must be hell for you around all those cell phone users in public.

My high school electronics teach was ex-navy (career man), very by the rules, strict as hell on safety issues in his shop. I doubt very seriously he would have allowed anything remotely dangerous or illegal.

The same circuit is availiable as a kit, from many online sourses, which would lend me to believe its legal and safe to use.

Back to the origional post...
Don't think it could work. 7404 is TTL, wouldn't 9 volts kill it? I'm guess it's wired as an oscillator, but seems like its a little light on parts. Every transmitter circuit I've seen (not a field of huge interest to me), has an inductor, usually a small hand-wound coil, just a few turns.

I don't know about pacemakers, but I can't imagine they are so sensitive to interference. There is a lot of strong electro-magnetic energy about, much more common and powerful than what could be produced by a 9 volt battery.
Must be a huge 'avoid a all cost...' list for pacemaker recipients, not to mention all the exercise, diet, and lifestyle do's and don'ts. Trying to avoid everything bad, and remembering to follow all those recomondations, remebering which medication at which time, with/without food... Wouldn't all that stress kill you anyway?

http://www.thinkgeek.com/gadgets/electronic/755e/ or try this ready made