where can i find a FM crystal oscilator for use in a small science project?

Question

needs to block fm signal from close range, i know its illegal but its in the name of science.

i have a crystal oscillator (i think) out of a CB radio. the markings say: STL 4.500 MHz 9844

its a little square thing with rounded edges with 2 wires coming out of one side and the entire opposite side is soldered to a circuit board.

Answer 1

Ramsey electronics has some decent kits. If you have $$, you can buy one.

Other than that, I'd recommend going to your library and borrowing the ARRL handbook. There's not many references so commonly available as that one which fill the need for knowledge so well.

Look for back issues of EDN magazine as well!

Answer 2

Yaktur is right. Ramsey Electronics is a good source for kits. If you have the skill, you can build your own from parts. Past issues of Nuts and Volts magazine is another source for such information. A large stack of "Hands on Electronics" magazines would yield some help as well. This magazine is no longer in print, but a library might have some.
Crystals in the broadcast FM frequency range do not exist. You need a third over tone crystal to reach such a frequency, but they are available. The transmitted signal, by the way, doesn't have to be modulated. If it is on frequency, and close to the receiver, the carrier wave will over power the radio signal and block reception. If you can't find what you need, get a frequency generator, that would also do the job. One other source would be an operating computer with the case removed.

Answer 3

According to the FCC regulation, (rough translation) purposefully interfering with another signal for the purpose of jaming or otherwise cause harm to the reception of the signal by the intended audience, is against the law.

In another words, if you jamm the FM broadcaster's signal, it is against the law, no matter how small your signal is.

BUT, if you are setting both of the transmitter, interfering with your own signal is not against the law.

With that said, you can NOT create a crystal element for frequencies higher than roughly 20MHz in the fundamental mode. Above that, you will need what is called an over-tone crystal, and even those will limit you to frequencies well below 50MHz or so. (below FM broadcast band) Beyond it, you will need to use technique as mixing and/or multiplying to get to your intended frequency. Long story short, you can not do it easily.

You could; however, purchase those transmitters intended to send signal for a very short distance, often used to send signals to your car's FM radio, as those are small transmitters, and you can legally use it for your purpose. They are often available from places such as Walmart, BestBuy, Circuit City, and many many online outlets.

Answer 4

You mean, how to get an FM transmitter for a small project. They are not illegal and are available everywhere! We use them on our XM radios. Radio Shack probably has them for TV.