Shortwave Receiver

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The following material has been taken from the 'Engineer's Mini-Notebook (Communication Project) pamphlet that can be found at your local or nearby Radio Shack store. (Catalog No. 276-5015A)

Radio Shack offers a series of pamphlets ranging from Communications to Digital Electronics. I have collected all 9 pamphlets. If you are ever in the store, do take a look at all the wonderful projects these pamphlets have to offer! The projects are very diversified, useful and simple to make.

I made this shortwave receiver a couple of years ago and it worked very well for me...being a novice at that time in the world of RF. It was from this project, that my fascination grew into the wonderful world of RF (radio frequency). Yes, if you are new to the field of RF or perhaps a veteran with many years accrued under your belt...this simple unit would still be a joy to make. So, if you are ready to bring in stations from half way around the world right into your living room...then begin your journey in making this unique little shortwave unit. Shall we begin?

Few hobbies are as rewarding or intellectually stimulating as shortwave listening. Yet many people have never listened to a shortwave radio. Even a very inexpensive shortwave radio can receive boradcasts from hundreds of stations around the world. Many of them are in English!

1) International Broadcasts - These originate from both private and government stations and are intended for a wide audience. Programming, often in English, includes news, weather, interviews, drama and listener mail.

2) Personal Communications - This category includes amateur and citizens band radio.

3) Utilities - Virtually all broadcasts not listed above can be considered utilities. These include time signals, computer transmissions, weather reports, satellite signals and many kinds of industrial and government transmissions. Included are tele-communications to and from ships, aircraft, taxis and commercial vehicles. Also included are transmissions from spy, radio control, tracking, surveillance, telemetry, weather balloon and ocean buoy transmitters.

Many of these transmissions are broadcast at frequencies between the broadcast band (that is, from 87 to 107 MHz) and 30 MHz. This simple receiver (located in the USA) received signals from Asia, Europe, South America and North America. The antenna was a 14 foot indoor wire.

Below is the schematic layout of the shortwave receiver. This receiver can be assembled on a solderless breadboard or a single-sided PCB. Continue with the construction below the schematic.

The form onto which the wire will be wrapped is a typical plastic film can. Wrap the can with 1-1/2" 2-sided tape. Then wrap the form with 30 gauge magnet wire at a width of 1-1/2", leaving both ends extend a couple of inches (later to be soldered directly to circuitry). Then take a piece of uninsulated 12 gauge solid copper wire and secure one end to the wooden platform and then bend it slightly to cover the whole width of the plastic film can. Where-ever the 12 gauge wire touches the width of the can, lightly sand off the enamel-coating on the 30 gauge magnet wire. This will ensure a continuity between the 12 gauge wire (called the slider) and the 30 gauge wire.

Most op-amp circuits, including the 741, require a dual polarity power supply. Below is a schematic drawing of how two 9-volt batteries should be arranged in relation to one another.

The antenna be be any gauge wire that is around 14 feet in length. Try and bring it up as high as you can inside the house. Through the ceiling and into the attic would be ideal!

Tuning is done by setting L1's slider (the bent 12 gauge wire) to any position and adjust C1. Change L1's slider position for broader frequency ranges.

CAUTION!!! Volume can be VERY loud, especially when L1's slider is moved AWAY from L1 and local stations can BOOM in loud! DO NOT USE EARPHONES!

This concludes the project of the shortwave receiver. I do hope you have many years of listening to stations througout the world! And should you need advice or help along the way, I am as close to you as your computer. I surrender this project to all and...