Build a very simple AM Transmitter.

If a crystal radio is the distilled essence of a radio, this transmitter is the matching distilled essence of transmitters.

The transmitter goes together in about 10 minutes, and is small enough to fit in the palm of your hand.


Depending on the antenna, the transmitter can send voice and music across the room, or across the street.


This is the transmitter off of http://scitoys.com .

Step 1: Stuff you need

Our transmitter will need these parts:

A one megahertz crystal oscillator
This is a crystal clock oscillator such as those used in computers. There are many suppliers, such as

An audio transformer

This is a 1000 ohm to 8 ohm audio transformer, such as Radio Shack #273-1380. 


A generic printed circuit board
I used Radio Shack's #276-159A, but any general purpose printed circuit board will do.


A phone plug
This should match the jack in your sound source. I use a 1/8 inch (Radio Shack #274-286A) plug to match standard earphone jacks of transistor radios and Radio Shack's Archer mini-amplifier speaker.


A 9 volt battery clip
I like the Radio Shack heavy duty type, part number 270-324.


A 9 volt battery

A set of alligator jumpers.
Radio Shack part number 278-1156, or you can find them anywhere electronics parts are sold.


Some insulated wire for an antenna.

Comments

[simonyu]

where does the audio-in plug into?

[rocketman221]

I tried it with a 50MHz crystal. It works surprisingly well for something so simple. I can pick it up on my police scanner set to 50MHz.

[Josehf Murchison]

What are the conections?

[mrmerino]

My crystal has two leads (and one ground). What do I do with it?

[electfire]

This is the exact same AM transmitter I built in 7th grade for science fair... If I remember right I was trying to test if high humidity effected how well the signal traveled... It was horribly not thought out well.... Basically I used a humidifier to create the humidity and a decibel meter to measure the volume from the receiving radio....

[skycarl]

Digi-Key has 1mh osc ic's. Here is one stock number CTX775-ND.
They cost about 4 bucks.

[Kiteman]

Why do you call yourself "SciToys"?

[Cameron657]

It's the name of the original website this guide was posted on.

[Kiteman]

I knew that - I was trying to check whether he had permission to re-post Simon's projects.

[gccradioscience]

I don't know how to create a instruct-able, but I did this using a LM-386 audio amplifer hooked up to the crystal oscillator, and the audio sounds great.

[silencekilla]

please post step by step instructions for the layout of the ciruit board and a shematic. also Spell Check is a very useful tool.. thank-you

[Cameron657]

Original page: http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html
Schematic: http://sci-toys.com/scitoys/scitoys/radio/xmitter_schematic.gif

[iPodGuy]

For such an interesting gadget, I really wish this instructable had step-by-step photos and links where to purchase parts. I am considering building a couple of either AM or FM transmitters, but I want to make sure I have a total understanding of what I'm doing before I begin.

I might have missed this info in the instructable, but can you give me the idea of the range that this transmitter has? I'd like to be able to make something that will cover around 150 feet or so.

[Cameron657]

Hmm, 1mhz crystals are extremely hard to find. The best bet is eBay, or the Scitoys website.

[jeff2967]

Can someone answer this question?

I could only find a 2 MHz Crystal, yet the 1 MHz crystal has 4 wires that are used in this project. What other components can i add/ or need to make this work with my 2 MHz crystal?

Thanks.

[Cameron657]

Won't work with a 2mhz crystal. We use 1mhz crystalls because 1mhz (or 1000khz) is right in the middle of the AM band. The AM only goes up to about 1.6mhz (1600khz) so you won't be able to find your transmitter on a standard radio. If you have a shortwave radio with a very wide coverage (i.e tuning staring at 1.6mhz/1600khz and up, you can pick it up on that. Otherwise there is nothing that you can do to make your 2mhz crystal work.

Also by the sounds of it, you have a CRYSTAL, not a CRYSTAL OSCILLATOR. An oscillator contains many other components other than just the crystal. That's why it has four legs, not two like yours probably is. Hope this helps.

[robot1398]

same pic on all steps................

[dungeon runner]

Nice toy. I wonder if this could fit inside of one of those altoids "smalls" tins?

[DarkStarPDX]

Five images, all exactly the same... I would recommend removing the duplicates! :-)