Is this schematic legal in the U.S.?

**broken link removed** Is this schematic legal in the U.S. Please tell me it is, because I have already bought some of the parts. If it isn't is there a way to make it legal? I know the frequency is legal, I just need to know the wattage. Also tell me how far you think it will broadcast. It sucks when you have to go through this much trouble to build a tiny little radio because of the FCC.

The 2n2222 says the power is in milliwatts. This radio is definitely in the commercial range (illegal) but the tiny watts might be permissable.

I hope someone else knows the limitations and will post the answer here.

Dx3

I would also suggest that other people have gone through the incredibly expensive and time consuming FCC process, and they sell modules that transmit and receive, legally. I saw an ad in Nuts&Volts magazine for these modules. I have no idea if that would serve your purpose.

The FCC limit is 100 milliwatts. I also saw a kit on electronics goldmine and it looked exactly like the circuit hear. two tramsistors,condenser mic,9v batery, etc. I dont want to buy a kit I would like to build it myself. I am at a low skill in soldering and what not, but practice makes perfect.

For a full run down on those limitation for unlicensed AM & FM transmissions, see 47 CFR Sections 15.207, 15.209, 15.219, and 15.221. You can read a synopsis here:

OET -- Bulletins On-line

I know the rules(the important ones anyway) I just need to know the wattage, and preferbaly your opinion on the distance it will transmit.

Hi,


The 100mw specification used to be based on a peak current measurement in the output stage (to determine max power output) but they changed that to allow for the advancement of spice models in doing simulations that are very close to real world measurements. Probably for many people though the current measurement would be good enough.

theruss007 said:

I know the rules(the important ones anyway) I just need to know the wattage, and preferbaly your opinion on the distance it will transmit.

Click to expand...

The FCC limitation is a specified field strength at 200' (61m). The maximum power out allowable for unlicensed transmitters in the AM band is likely in the 1 milliwatt area dependent upon the antenna gain, which establishes the effective radiated power (ERP) which is the basis of field strength at a given distance.

If you don't want to take the time to read the FCC information provided, at least read the disclaimer at the site you posted. NOTE that the provider did not claim FCC compliance for the transmitter and that the provider disavows responsibility.

I did read the disclaimer and it says that is ilegal in the U.K. As for the 1 milliwatt power rating you may be right. I will read into it know. As for the link you posted, I don't like downloading stuff because I have slow internet and a download limit.

After deciding to look at the link, it gave me no real info on the limits of a AM transmiter other than the operating freqency. I have been able to find out tthat the field strength is more important than wattage. I believe that the field strength can noot exceed 250 millivolts at 3 meters/10 feet. You would think it would be quite easy to find the limits of a unlicensed radio, but it isnt. I think I will build it any way. Im not going to use it as a mini broadcast station. I will build it make sure it works and put it on a shelve thats about it.

theruss007 said:

After deciding to look at the link, it gave me no real info on the limits of a AM transmiter other than the operating freqency. I have been able to find out tthat the field strength is more important than wattage. I believe that the field strength can noot exceed 250 millivolts at 3 meters/10 feet. You would think it would be quite easy to find the limits of a unlicensed radio, but it isnt. I think I will build it any way. Im not going to use it as a mini broadcast station. I will build it make sure it works and put it on a shelve thats about it.

Click to expand...

The info was there on page 13. I thought I mentioned the bit about field strength...guess you missed it, but found the info elsewhere...good on ya!. If you look at page 13 of the link I posted, you'll see the emission limit of (24,000/f in khz) uV/m at 30 meters. That would put that point at a max level of 24uV quasi-peak at 1Mhz. At the 61m limit for unlicensed transmitters that would place the max limit at less than 17uV at 1Mhz. Working backwards to 3 meters, that would place the limit at that distance at ~13db below the 250 mv/m level you found or whatever.

It wasn't that hard to find the information, I think, but then I'm may have been around a tad longer. Yes, by all means go ahead and build it...good experience and learning tool.

Yeah, I am goning to build regardless. Even if I did test the signal strenght etc., I would have to buy a meter for it. Who knows how much that would cost. I think I may have clicked on the wrong link after clicking the one you posted, so thats why I didn't find anything. But, what I meant by easier to find I mean google once find what you need and be done with that. Not have to start a forum and read 20 pages of FCC regulations.