Hey can anyone give me a summary on FCC's rules on unlicensed intentional radiators? What frequencies can I legally transmit at, and what are the power levels? Thanks for any help, I just don't want to have a cop at my door if you know what I mean..

 

Check out Citizens Band--while they 'license' operators, it is so far out of control that few do this anymore--also while the 5W power limit is often severely violated, prosecutions are rare, I think--main thing is to make sure that your harmonics are low so they are not causing interference

 

Ahhh, citizens band is only for non-continuous voice transmission, and you are supposed to use your station identifier (or at least you were supposed to a number of years ago).

It's your responsibility to know the FCC rules, and you need to know that the FCC has absolutely no sense of humor - they can seize your equipment, throw you in jail and assess heavy fines ($10k for each infraction); so it's nothing to take lightly.

You really need to clearly state your requirements; what are you planning on doing via RF, and what is it that you really need to do?

Can you use pre-built radio modules; transmitters in particular?

Receivers aren't much of a problem; you can listen to just about any frequency without getting into trouble. It's transmitting on unauthorized frequencies and/or at unauthorized power levels that will get you in trouble in a big hurry.

If you are dead set on building a transmitter, you really need help from someone who has an FCC license AND suitable test equipment. In this case, I suggest that your best resource will be the ARRL:
http://www.arrl.org/

I suggest that one of the first things you'll want to do is find an ARRL affiliated club. Here is the search page for finding clubs:
http://www.arrl.org/find-a-club
Seek a mentor at a nearby club. You really need someone to closely look at your design, and test your transmitter to ensure that it is within FCC regulations. This can't be done economically via the WWW; you need hands-on local help - or else you will spend a LOT of money on test equipment, and then have a steep learning curve on how to use them.

After becoming an ARRL member, you should buy an ARRL handbook, available on this page: http://www.arrl.org/shop/What-s-New/

If you need something relatively quickly, you need to consider transmitter/receivers that are already assembled and meet FCC regulations.

 

Really want to keep the cops away - don't do it or abide by FCC part 73. Read it, do it, be legit! http://transition.fcc.gov/mb/audio/bickel/amfmrule.html

 

Your transmitter fundamental frequency or any of its harmonics must not cause interference to police, ambulance, fire department or airplane radios. If it does then they will find you with their truck with the rotating antenna on top then they will chop off your head (or shoot you or both).

It must not cause interference to radio or TV.

If you don't get caught then you will be lucky.

I got caught when I was 18 years old, but here in Canada the RF cops are nice guys. They let me go with only a warning.

 

This might be of some use to you: http://www.hobbybroadcaster.net/

 

If you want to have a radio station then you should have a good circuit:
1) Many simple circuits have radio frequencies that drift all over the place which causes interference. Modern radios cannot receive the varying frequency. The frequency should be set with a crystal controlled synthesizer.
2) Many simple circuits sound awfully muffled because they are missing the treble boost (pre-emphasis) used by all FM radio stations. All FM radios cut the treble (and therefore cut hiss) so that the sound is normal. But then all radios cut the treble from a simple transmitter that makes it sound muffled. Even AM radios stations boost the treble because most AM radios cut frequencies above only 2kHz.
3) Most simple FM transmitters are mono, not stereo.

In about 1962 I made a stereo adapter for my kit FM tuner then the stereo sounded fantastic! That was 50 years ago.

 

Thanks for all the replies. I'm not going to be doing anything high power, a range of 15 meters would be great. I'm also wanting to transmit digital data, not analog. While on google I came across this: http://louise.hallikainen.org/FCC/FccRules/2011/15/209/ "
(a) Except as provided elsewhere in this subpart, the emissions from an intentional radiator shall not exceed the field strength levels specified in the following table: Frequency (MHz) Field strength (microvolts/meter) Measurement distance (meters) 0.009-0.490 2400/F(kHz) 300 0.490-1.705 24000/F(kHz) 30 1.705-30.0 30 30 30-88 100** 3 88-216 150** 3 216-960 200** 3 Above 960 500 3"

So in theory, I could legally transmit at say 40Mhz with a field strength of 100uV/m at 3 meters?

 

Here u can blast away...

 

If you only want a few meters, then you may not have to worry about the FCC with simple one transistor, low power transmitters.

http://www.cappels.org/dproj/FMdist/fmdis.htm
http://electronics-diy.com/electronic_schematic.php?id=812

 

You could just buy a couple of cheap low-power digital transceiver modules which are already approved for use in your country. They used to be about $10 each but the price is closer to $5 each these days if you look on ebay.