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Picture of 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

Picture of 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.
 
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Phil B (author)  abadfart6 years ago
Back in the 1920s and 1930s there were plans for AM and SW radios you could build at home. Most of them had coils you could remove to plug in a different coil for receiving a different range of frequencies. There might be a coil you could remove or alter, but I would have no idea about specs for making the coil to replace it. Some radios, like scanners, use different crystals to select different frequencies.
could i possibly add a switch to the 7 turn coil to turn the SW off and go back to AM? the radio i have is an AM/FM is there a way to tell which side to connect to?
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Phil B (author)  mikemmcmeans6 years ago
To switch back to AM from SW you need to remove the seven turns of wire you added. Just disconnecting one of the leads did not eliminate SW reception and restore AM reception for me. Unfortunately, there is no way I can tell you to which tabs you will need to connect the ends of the wire for the extra coil. You can try to guess it out, but finally, it will be a matter of trial and error. And, there is the possibility it will not work on your radio.
jcomtois Phil B6 years ago
Tuning circuits are touchy, but if you disconnect BOTH lines from the 7-turn coil with a double-pole switch you might get back to the original AM tuning. I have some old hand-built radios and that seems to be how they handle switching some of the frequency ranges, and sometimes they did it just plugging in different coils like Phil B says. You may have to adjust those trim caps (the screw settings) to get exactly back to the original "AM" broadcast range. Make small adjustments at a time.
static jcomtois6 years ago
As you said tuning/ tuned circuits are touchy. Even with switching the added coils out of the circuit, their mere physical presence, may affect the original operation, May not either, can't know until you try. BTW all, most of the signals in the short wave bands are AM, anyway until they go to digital.
could he gut another radio an add switch to both on being AM the other being SW an just have one of them taped with eletrical tape protecting the wires on the outside od the radio ?
Phil B (author)  riverreaper6 years ago
It might work if he canabalizes an identical radio. Any change in circuit design or specifications might change the outcome entirely.
Very interesting Instructable! How does the addition of a seven-turn winding on top of the existing antenna enable shortwave reception?
Phil B (author)  Infinitevortex6 years ago
Reading about tuning circuits, also known as tank circuits, answers the question. A tank circuit is a variable capacitor in parallel with an inductance (coil of wire). At a specific frequency an inductance has a unique amount of resistance, also known as reactance, to a signal current traveling through it. Reactance from a capacitor works to cancel the reactance from an inductor. Turning the shaft on a tuning capacitor changes the capacitive reactance presented to the signal current until the point is found at which the capacitive reactance cancels the inductive reactance for that frequency. At that point all frequencies above or below this signal current frequency are attenuated, or blocked. Only the desired frequency passes to the rest of the radio circuit. Adding a few turns to the coil on the ferrite rod changes the inductance so that a different frequency passes when the tuning capacitor is in a particular position. In this case, seven turns was about the right amount to throw the range of frequencies that can be tuned into the 4 MHz to 9 MHz shorwave range. I like to think of the front wheels on an automobile. Let us say both have a serious amount of toe in. The left wheel wants to push the car to the right. The right wheel wants to push the car to the left. At some position the steering wheel is able to make the car go straight down the road. Change the toe in on either wheel, and a new position on the steering wheel needs to be found for the car to travel straight.
Thanks, thats fascinating! I'll have to investigate those tank circuits further. In this example, the added coil is in parallel with the existing one. Would it make any difference if the seven turns were in series with the coil?
Phil B (author)  Infinitevortex6 years ago
I am glad my feeble explanation made sense to you. Watch out, though. Soon you will be stealing time from your other responsibilities to read tattered electronics books you found in dark corners at libraries and bookstores. On garbage day you will sneak around your neighborhood looking for discarded electronic devices that you will carry home under your coat so you can hide them in your room until you think you are alone and have time to coax out their secrets. Adding a coil in series would change the inductance, but perhaps not as much or in the same way. I do not know.
Phil B (author)  Phil B6 years ago
If you "rescue" any old TVs from the curb for parts or experimentation, be very careful. The tube acts like a large capacitor and holds a deadly charge for a very long time. Get some good instruction on how to discharge it safely. On the bright side, many TVs have a small fuse on the circuit board. There are folks who discard a TV without checking to see if the problem was only an inexpensive fuse.
That's good advice. Be careful with CRT computer monitors, too, as they also contain large capacitors. Thanks for the fuse tip. It just might come in handy some time!
Phil B (author)  Infinitevortex6 years ago
If you liked the way tank circuits work, have you ever read about superheterodyne radio circuits and why they are superior to tuned radio frequency or regenerative radio circuits? I really enjoyed learning about superheterodyne circuits.
I believe I did ,once, but I didn't really understand what the book was talking about. Recently, I was given a large quantity of old electronics books which I hope to go through when I get the time.
Phil B (author)  Infinitevortex6 years ago
At the risk of boring you with unsolicited commentary, a tuned radio frequency set tunes in a station, strips audio away from the radio frequency and amplifies it to make sound. A TRF circuit is fairly easy to build, but it works pretty well at some radio frequencies while not working very well at others you may want to tune in. A guy named Armstrong solved the problem when he came up with the superheterodyne radio. It adds something called a beat frequency oscillator. Imagine you hear a musical note. It has a frequency. Suppose a second note is played at the same time. One beats against the other and the two blend together to make a sound at a frequency different from either of the original two. Suppose you could manufacture and manipulate a frequency to beat against the frequency of the radio station you want to hear so that the combination of the two frequencies always resulted in the same final output frequency, regardless of what station you want to hear. You could then build all of the detection and amplifying stages of the radio to handle this one frequency very efficiently. You could do this because you are changing the beat frequency as you tune the radio so that the combination of it and the station's broadcast frequency is always the same. That is why modern radios have two sections in the tuning condenser. One section tunes the tank circuit and the other tunes the beat frequency oscillator.
static Phil B6 years ago
Actually the second capacitor section tunes the local oscillator. While the local oscillator output frequency beats against the frequency of the desired signal to create the intermediate frequency, the Beat Frequency Oscillator, serves another function. While every superhet receiver has a least one local oscillator very few have the BFO. Only receivers that are constructed with CW (Morse code) and simple (poor) Single Side Band reception in mind, have the BFO. While these simple tricks do allow a medium frequency broadcast band receiver receive broad cast signals in the short wave bands, it's a trial and error process, where what works on radio may not work on another.
Very interesting, and it wasn't boring. Thankyou!
Thanks. I already have an old Beta VCR under my bed, (in addition to a lot of assorted computer and electronic junk)!
inductance is the same as resistance in terms of straight adding in series and inverse law adding in parallel. In series just add the inductance total = I1 + I2 + I3.... In parallel, 1/total inductance = 1/I1 + 1/I2 + 1/I3 ...
Wow, this is a really good project, and a good story, too, well done.
Phil B (author)  Gamernotnerd6 years ago
Thank you for your comment. I meant to make it clearer that I heard the Australian radioman interview on the little travel alarm/radio pictured in the Introduction after I had converted it for SW listening. I was asked to make a presentation to a group of gifted 6th graders at a school, and did this. A father came home that day and found his son with the radio the father had given the son's mother as a wedding present. It was in pieces on the dining room table. When the son explained the father got interested and they were able to listen to SW programs on the radio. Another student came home and told her parents about my presentation. They had escaped from mainland China and showed their daughter the SW radio they had used in a refugee camp before they were resettled.
Wow, this conversion sounds pretty sueful, I might just have to try it, would you, by any chance know where to get a cheapy radio in the US?
Phil B (author)  Gamernotnerd6 years ago
I would think you might find some cheap radios at yard sales and such. Shortwave (SW) broadcasts are not as plentiful as a couple of decades ago. I used to get the Moscow, Austria, Germany, Australia, the BBC, Canada, Voice of America, Switzerland, Finland, Ecuador, Prague, Cuba, Taiwan, China, Japan, and probably some others. Now I can get China, Cuba, a variety of Spanish language stations, and some religous stations in English. Their is also WWV, the time standards station from Fort Collins, CO. It was a lot more fun back in the 1980s and before.
mistic Phil B6 years ago
I boughta junk Hallicrafters that was of 1975 vintage, multiband to 28MHz.It worked perfectly when I cleaned the band switch contacts. I still get Moscow, Germany etc.. .
Phil B (author)  mistic6 years ago
Hallicrafters was a good name. I got more SW broadcasts when we lived in East Tennessee than I get in Idaho. I noticed a lot of broadcasts were being eliminated about ten years ago due to budget cuts, a move to digital broadcasting, and Podcasts on the Internet. I have downloaded schedules for Deutsche Welle and North American broadcasts are non-existent in German. I did not check for English broadcasts. But, I do notice scanning the bands during the evening turns up very little.
Thanks a lot, I'll be looking for a nice little radio!
kostya6 years ago
Nice project! Congratulations! Can I replace the winding (7 turns) with a small inductance (looks like a .25W resistor) to pick up SW stations? What sort of antenna would you recommend to listen to DX stations?
Phil B (author)  kostya6 years ago
I doubt that you can tell the effect of an inductance by looking at it, just as all 1/4 watt resistors may be the same physical size, but vary considerably according to the actual resistance of each. You can always make an addition or substitution and see what happens. Just be careful not to do something you cannot reverse. People have all sorts of antennae. Do some reading on long wire dipole antennae tuned by length to the frequencies you want to receive by 1/4 wave or full wave. A lot depends on whether you have physical space to stretch out a long antenna.
idrawupay6 years ago
This a great project. To get back to AM could you add another AM tuning coil thats unmodified. Then switch between the 2 coils?
Phil B (author)  idrawupay6 years ago
I do not know. It would probably depend on the exact circuit design on the radio you have. It might be less of a bother just to have a second small radio for AM listening. The basic idea in this Instructable is a novelty that is fun to do as an experiment. If someone is genuinely interested in listening to SW broadcasts regularly and has any normal resources available, a small commercially produced AM/FM/SW radio would be more practical. Some cheap models are often available. Better SW radios do not have some many hisses and howls caused by a lack of refinements in the circuitry. SW broadcasts are more prevalent in parts of the world outside the USA.
Just add a switch in series with the new coil. Just keep in mind that this will affect the inductance of the circuit. You may only need 6 turns. Or 5.5. You will have to experiment. The exact change will depend on the specifics of how the wire is run, length, etc. Try it at home.
Good project, Phil. For CADDBOY: short wave is AM, too. The difference is only the wave length (or frequency, that is inversely proportional).
Phil B (author)  rimar20006 years ago
Thanks, Rimar.
bustedit6 years ago
Neato, and very easy looking. 7 turns is the key? if even spacing is ideal, would it be detrimental to use tiny drops of hot glue to secure the wrap?
Phil B (author)  bustedit6 years ago
Droplets of hot glue or even parafin could hold the turns of wire in place. A strip of masking tape would probably work, too. I converted three or four radios over the years and never worried much about equal spacing of the turns, nor about fixing them in place. You might be interested in the second paragraph of my response to gnomedriver in answer to your question about seven turns of wire being the key. It was all a happy accident.
gnomedriver6 years ago
Great instructions and stories. I would never have thought it would have been so simple. I suppose by experimenting with the number of windings and spacing of loops other bands could be received. I wouldnt travel without a small SW radio. I setup long length of wire as an antenna around the hotel room and hunt down the BBC, Radio Netherlands or Deutsche Welle. I got into SW radio when I was travelling. I liked the challenge of trying to pull in a clearer signal. Often the challenge is more enjoyable when simple equipment or something like your adapted radio is used. I get more enjoyment using my small radio than the Sony ICF-SW7600GR for have for home use.
Phil B (author)  gnomedriver6 years ago
Thanks for your comment. You must be traveling in Europe to receive those stations these days. People who like SW radio concoct all sorts of things for antennae. One guy hung a pleated piece of aluminum foil on the hotel room curtain and it worked for him. I discovered I could get SW with seven turns of wire around the ferrite rod antenna entirely by accident while I was trying to make something else do another task. That failed, but all of a sudden I heard the interval signal for Radio Canada. I started listening to SW because I had taken a couple of years of German in college (mostly for reading) and wanted to learn to understand spoken German. I bought an SW radio and began listening to Deutsche Welle. Your comments about getting by with minimal equipment reminds me of amateur radio operators who like flea power. They use simple homemade sets they run off of a car battery with a long wire antenna and often log contacts on the other side of the world.
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