Instructables

Listen to Shortwave Broadcasts on an AM Radio

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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.
 
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Step 1: Not as popular as before

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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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dmagryta1241 month ago

I did this project, with very rushed and very sloppy craftsmanship, and much to my surprise it works! I'm able to pick up only a few overlapping channels; a morse channel or CW beacon of some sort, and a very distant foreign channel. I just clipped the antenna wire to a wire basket, and the reception is just fine that way. Great instructable! Thanks!

Phil B (author)  dmagryta1241 month ago
I am glad it works for you. On the one hand, I miss the wide variety of things that were available on shortwave bands twenty years ago. But, on the other hand, I really like the crisp clear audio I can now download from the Internet and play anywhere, even in my car. Thank you for trying it.
sconner16 months ago

Do the new wraps need to be in the same direction around the ferrite as the original factory coil?

Do the new wraps extend the coil in a serial connection or parallel it?

Phil B (author)  sconner16 months ago
I paid no conscious attention to the direction of the windings relative to those already on the ferrite coil. The windings are in parallel.
Cambenora9 months ago

Cool project. I'm going to try this one. Thanks!

Phil B (author)  Cambenora9 months ago
I hope it works well for you.
oh ok thanks
what if your ferrite rod antenna is farther away from the variable capacitor and the 6 inches of wire wont reach it, can i just cut the magnet wire longer?
Six inches was only an approximate length for most radios. Go ahead and use a longer piece according to your needs.
This is brilliant. I have dug out my old Realistic DX-350 and started listening to SW. It is fascinating. If I did this to a AM radio for my kids to play with, would there be a way to make it switchable to preserve AM functionality or does the loose coil adversly effect the AM signal?
Phil B (author)  BigBadgers20012 years ago
I expect you could put a switch on the coil windings you add. Try disconnecting one leg to see if that works. If it does not, try disconnecting the other end of the coil and see if that works. Add a single pole or a double pole switch according to what you find.

You will need to help your kids understand tuning an SW station on a modified radio like this requires a lot of patience because a signal is just a blip on the dial.

I do not listen to much SW radio now because broadcasts I would want to hear are available now as Podcasts I can hear on my schedule in much better quality than I got with SW radio.

Thank you for your comment and for looking. I hope you and your kids find enjoyment and success in your efforts.
Chakazuluu2 years ago
Wow you brought back some memories. When I was in elementary school (I am 70 now) my father had an old stand up Philco Am and shortwave radio. I sandwiched a piece of aluminum foil between two pieces of card board with two screws connecting the two antennae wires and put it under the dial phone we had. It brought in some amazing frequencies.

I think I will do this with an old AM radio I have. Thanks for the memory.
Phil B (author)  Chakazuluu2 years ago
You are four years older than I am. We had a similar radio, but ours was a Zenith. For whatever reason, I do not remember ever getting a shortwave broadcast on ours. At the time I do not think I knew to attach an external antenna. I am guessing that what you did coupled with the telephone lines by capacitance to make use of them as an antenna.

Thank you for looking. I hope you are able to make your old AM radio receive some shortwave broadcasts. I think I may have mentioned it worked pretty easily on one radio, but not so easily on another radio I still have.

Shortwave has been a lot of fun. Regrettably, the band is not nearly as full in recent years, although at night I still hear a number of things in Spanish. Radio Havana broadcasts in English and there are some Christian broadcasters. I miss things like Radio Canada, Radio Austria, Radio Australia, etc. Thank you for looking.
Now that you mention it ours was a Zenith also I thought it was a Philco but when you mentioned Zenith suddenly the memory came back. I got the aluminum foil antennae idea from a short blurb in Science and Mechanics.
Phil B (author)  Chakazuluu2 years ago
If you go to this link, I think the radio shown is very close to the one we had, if not identical to it. Several details I remember correspond. I am not sure of other details.
Oh my goodness I can't believe this it is precisely the same radio we had. It is like you took me back in time and opened up a flood of memories that was seemingly forgotten. It is like a door to the past has been opened and I can see situations and occurrences clearly that was fuzzy and inconclusive. I need to ponder on this for a bit.
Miketan3233 years ago
Its weird, I'm picking up stations in the 10-15 kHz range. Hmmmmm...
Phil B (author)  Miketan3233 years ago
Good for you. It is working. You have shifted your radio's frequency range to the 10 to 15 MHz range. My experience with my radio was the 4 to 9 MHz range, as best I could tell. Perhaps it is a difference in radio circuitry.
Johenix3 years ago
Recognizing CW operators by 'FIST' dates back to the American Civil War (War of Northren Agression) when a Confederate telegrapher spotted the strange sending of a Union intercept tap operator and sent: "Get off the line you damn yankee!"
I have a huge digital Aiwa stereo on my living room, it can tune Am, FM and SW but I've never been interested on SW. Gonna attach its antenna and try to listen to it sometime. :)
charlieb0004 years ago
i have a car radio i bought ages ago but never installed. it is not PLL, but very simple. it has little coils soldered into the board near the tuning cap but no ferrite. it also has a few (maybe six) metal boxes with painted ferrite inside. how can i convert this? it would make an excellent reciever as the tuning knob is really geared down and takes 16-20 turns to go accross the band. i guess i can do it as instructed with some ferrite, but the tuning cap has six pins and i dont know which to join to it.
Phil B (author)  charlieb0004 years ago
I do not know enough about car radios to say if it is possible.  You can, however, order a shortwave converter for your car radio.  Here is one link.  But, it is not cheap--about $165. 
I found this i'ble just in time. I have an on-going project on pause so I think I'm gonna turn it into a shortwave radio to pick up my friend's Morse code.
Phil B (author)  nutsandbolts_644 years ago
It should do that for you.  This makes an interesting receiver.  But, it is not always a great receiver.  I hope it does what you need.
 If I can find it that is. 
I used to get SW stations back in 1991 with a cheap $20 radio, but the radio fell apart, but I have kept in touch with the world.   The radio was a portable Windsor TV/AM/FM/Weather radio.   I also had a friend that was picking up shortwave broadcasts on his AM/FM clock radio until I told him to put the ferrite rod back in place.   It was a new come back experience.    Now I feel I might experiment again.
Phil B (author)  gccradioscience4 years ago
Thank you for trying this modification and reporting back that it worked for you.  It makes a crude shortwave receiver without some of the circuit refinements in modern receivers, like spurious signal rejection and phase locked loop (PLL) controlled tuners.  Your friend's experience with the presence or absence of the ferrite rod on his clock radio is interesting.  The early 1990s was the height of my shortwave listening experiences.  The number of stations I am able to receive currently is only a shadow of what was available 20 years ago.  But, I now download Podcasts from some of those same stations and convert them to CDs I can play in my car.  My aim was to improve at understanding spoken German.  Although I miss the shortwave broadcasts, the audio quality on the Podcasts is far superior to anything I ever heard on shortwave.   (During the first Gulf War I once heard a news item on shortwave that did not make the news reports in the USA until two days later!)   
I tried it,  it works very good, except it drifts alot, it takes patience to tune and experimentation.  I also used one of my indoor shortwave radio antennas.    What a great way to get access to world band on a radio you do not use.  Great Job!  
static5 years ago
For whatever reason I was lead back to this instructable, so I thought I would search out and post some links for the noobs. I did find a schematic for the typical transistor radio here http://my.integritynet.com.au/purdic/am_rec.htm . Go here to find the link to part 2 it's in the left column as you scroll down the page. You can read the USN electricity and electronics train publications here http://www.tpub.com/content/neets/http://www.tpub.com/content/neets/ The documents can be downloaded free as well, but I can't find my bookmark for doing so. OK here it is, this will keep nerds busy for awhile.
static static5 years ago
Came back to get an url I failed to bookmark, and notice errors in my post, Exclamation deleted.

Read the USN training docs here http://www.tpub.com/neets/
Download them here http://www.tech-systems-labs.com/navy.htm
Very interesting Instructable! How does the addition of a seven-turn winding on top of the existing antenna enable shortwave reception?
Phil B (author)  Infinitevortex5 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.
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Repost to correct a typo. What they had you construct was a common mode choke. To choke any RF on the outside of the coax braid, so it wouldn't act as a radiator. Sometimes it helps with RFI problems, sometime it doesn't. Yes inductors(coils) do many things, our modern world wouldn't exist without them. so it would act corrected to so it wouldn't act.
Phil B (author)  riverreaper5 years ago
Radio experimenters sometimes add coils to antennae to preselect the desired frequency and attenuate undesired frequencies. This is supposed to be a helper for the tank circuit and may make it possible for weak stations to be received. It does not change the range of frequencies the radio can receive. The inductance I added to the tuning or tank circuit had the effect of changing the range of frequencies the radio could receive. So, it is not quite the same as what you did.
66411 Phil B5 years ago
Another good way to learn about tank circuits is to build a spark gap Tesla coil, by changing the length of the primary coil, you change the frequency that it generates. For maximum efficiency, you want the capacitor and coil to resonate at the same frequency. I find that this website offers a good explanation on the operation of a Tesla coil.

static 664115 years ago
Then again the coil diameter. wire size and spacing/pitch as well as the capacitor values all effect the resonant frequency of tank circuits. No doubt some where on the web are good tech training videos that illustrate well what's going on in a tank circuit, and component value ply into the whole thing. The old black and white army/navy films help out a lot.
Phil B (author)  664115 years ago
Thanks for the comment and the information. Tesla coils have always seemed interesting, but I never pursued them.
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)  Infinitevortex5 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.
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