Intro: Listen to Shortwave Broadcasts on an AM Radio
The larger radio is my Sangean ATS-803A shortwave receiver. The smaller radio in the foreground is a travel alarm/AM-FM radio from the late 1980s. I converted it to receive shortwave frequencies between 4 and 9 MHz and used it that way for a while. You can make a like conversion on an AM radio you own.
For those with a deeper interest: Once while vacationing in Oregon I heard a broadcast from Radio Australia about a radio operator on a naval ship who learned to recognize the "fist" or touch of wireless operators from other ships before he heard their call signs. When WW II was about to break out the German radiomen ceased using their call signs to hide the identity of their ships and their location, but he knew each one from his distinctive "fist" on the Morse code key. The radio signals also modulated in a distinctive way when a ship was transmitting from one particular area. Not only could he identify the German ships from the way the radiomen tapped out their Morse code, but he also knew exactly where some of the ships were located at the time. This is just an example of things you can hear on shortwave broadcasts.
Step 1: Not As Popular As Before
Shortwave frequencies bounce off of the ionosphere and return to earth halfway around the world. It is easy to receive broadcasts from another continent; depending on conditions, time of day, signal strength, and target area for the broadcast.
Pictured is the Passport to World Band Radio. A new edition is published each year. It is a yellow pages guide to international broadcasts.
Unfortunately, shortwave broadcasts are not as available as a couple of decades ago. This is due to budget cuts and the Internet. Now you can download Podcasts from many national broadcasters. These Podcasts are in FM quality and without the static interferences associated with shortwave broadcasts. Still, there is a certain romance from listening to a radio signal from the other side of the globe.
Step 2: Open Your Radio
Select a radio with analog, not digital, tuning. Open the back of the radio. Look for the ferrite rod antenna and the condenser or capacitor tuning block. The ferrite rod is the black rod with flesh colored wire wrapped around it. (See the top of the photo.) The tuning block is the translucent plastic block you see with trimmer screws on the back surface of it. There are solder tabs around the tuning block. A boom box works better for this project than a small radio because the much larger ferrite rod pulls in a better signal.
Step 3: Magnet Wire
Get some magnet wire from an old motor, ballast, or transformer. Or, you can buy a set of small spools from Radio Shack. #26 is about the right size. The pencil included in the photo is for scale better to perceive the size of the wire. Cut a piece about six inches long and scrape about 1/8 inch or more bare on each end.
Step 4: Loosely Wrap Seven Turns of Wire
Wrap seven turns of magnet wire around the flesh-colored coil on the ferrite rod antenna. The turns can be a little loose. Spread the turns out as evenly as possible over the length of the flesh-colored coil.
Step 5: The Circuit
Below is an electrical diagram of what you are trying to accomplish. The easiest radio for this conversion has only an AM band. Then you can solder the ends of the wire you wrapped to the tuning block terminals where the very fine wires from the flesh-colored antenna coil attach to the tuning block. It is a little more complicated when the radio also has an FM band with additional connections to the tuning block. The trick is to find the two tabs on the tuning block for the AM band. A good clue is when local AM stations are no longer heard as you tune across the radio dial. Attach ten to twenty feet of wire to one end of the small coil you added. This will lay across the floor as an antenna. Close the back of the radio.
It is possible that a radio you have will not work with this conversion. I have just such a radio, but have also successfully converted several other radios.
Reception is generally limited to hours of darkness. Evening will be the best time. Tuning can be difficult. Stations may be no more than a blip on the dial, requiring a constant gentle pressure from one side or the other on the knob or wheel to hear the broadcast. A smaller radio may require earphones in order to hear. A boom box will be easier to tune and to hear without an earphone.
I knew a Chinese couple and offered to convert their boom box's AM band for shortwave. I finished the project and gave it back to them four days before the massacre at Tiannamen Square happened. Every evening after they closed their business they were glued to their radio. Radio Taiwan gave accurate reporting. Radio Bejing glossed over the story and played classical music. Both had relatives in Bejing (Peking). Not only had I experienced a success with the conversion, but I helped out this couple and they were very appreciative.