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Is it possible to make a 20 MHz radio with this

enter image description here

by creating a circuit consisting of a battery, that crystal oscillator and an antenna?

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You already accepted an answer, but I think you should wait a little so your question gets more attention of others too. Also I think you should elaborate a bit on what the goal is you want to achieve. Is there modulation? AM? FM? PM? Is it a analog signal you want to receive? digital? ... – jippie Jul 13 '12 at 7:27
@jippie - He can accept a different answer at any time. Happened to me several times, in both directions. – stevenvh Jul 13 '12 at 7:34
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@stevenvh I know, but you can only go up to 65535 rep and then it resets to 0. I want to protect you from that ;o) The main reason for my comment is I think accepted-answer questions get less attention. – jippie Jul 13 '12 at 7:39
@jippie - damn, I was going for 4 294 967 295 :-). Just as long as it doesn't go down to -32768. But you're right, though I often answer questions with an accepted answer (and sometimes these answers get votes too). Oli also answered this one. – stevenvh Jul 13 '12 at 10:05

2 Answers

up vote 3 down vote

No. It's not an oscillator, it's just a crystal. You'll have to build an oscillator with it yourself, which only requires a few components, for instance like this one with a FET:

enter image description here

If you don't want to build the oscillator yourself you can also buy them for a few dollars. Then you don't have to worry about stability and such.

enter image description here

The oscillator won't give you enough power to drive a 50 Ω antenna, but an HF amplifier following the oscillator will do the job.

edit
That gives you a "radio", but it just transmits a fixed sine wave(*), your 20 MHz carrier, no signal. For FM or PM you'll have to modulate the oscillator's frequency. AM can be done at the amplifier stage. CW (Continuous Wave) for instance just switches the carrier on and off.

(*) The encased oscillator shown outputs a digital square wave, so you'll have to filter that, otherwise you'll transmit 20 MHz, 60 MHz, 100 MHz, etc.

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Oh, it was under the "oscillator" tab, my mistake then I guess. – Harry Svensson Jul 13 '12 at 6:21
@Harry - They mention the use with a microcontroller, and that's indeed where it's often used. The microcontroller has an oscillator on board, which has two pins to the outer world where you connect the crystal, and a few capacitors. – stevenvh Jul 13 '12 at 6:32
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These oscillators are brilliant to produce a given static frequency, but they are hard/imposible to modulate or to use in a demodulator. – jippie Jul 13 '12 at 7:24
@Harry - On this otherwise excellent site they also seem to call the crystal oscillator. As a matter of fact it is the oscillating part in an oscillator, but you also need the amplifier. – stevenvh Jul 13 '12 at 14:16
up vote 0 down vote

If you really mean just an oscillator (the crystal is only part of one as Steven says), a battery and an antenna, then the answer is no, not a radio that will be of much use anyway.

All this would do is create a 20MHz carrier frequency which you will need to modulate somehow in order to transmit information. This could be as simple as a on/off switch (e.g. morse code) or some more complex form of modulation.

Knowing a bit more about what you actually want to transmit would help provide a better answer.

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