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.

Comments

[Chakazuluu]

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]

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.

[Chakazuluu]

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]

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.

[Chakazuluu]

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.

[Miketan323]

Its weird, I'm picking up stations in the 10-15 kHz range. Hmmmmm...

[Phil B]

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.

[onlinemastering]

I have to admit being a bit of a "anorak" myself and still like to tune round the SW bands at night. I especially like it as you do not know what new ethnic music you might discover next, very entertaining.cheers

online mastering

[Johenix]

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!"

[elias.alberto]

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. :)

[charlieb000]

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]

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. 

[nutsandbolts_64]

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]

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.

[nutsandbolts_64]

 If I can find it that is. 

[gccradioscience]

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]

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!)   

[gccradioscience]

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!  

[static]

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]

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

[Infinitevortex]

Very interesting Instructable! How does the addition of a seven-turn winding on top of the existing antenna enable shortwave reception?

[Phil B]

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.

[riverreaper]

(removed by author or community request)

[static]

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]

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]

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]

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]

Thanks for the comment and the information. Tesla coils have always seemed interesting, but I never pursued them.

[Infinitevortex]

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]

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.

[Infinitevortex]

Thanks. I already have an old Beta VCR under my bed, (in addition to a lot of assorted computer and electronic junk)!

[Phil B]

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.

[Infinitevortex]

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]

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.

[Infinitevortex]

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]

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]

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.

[Infinitevortex]

Very interesting, and it wasn't boring. Thankyou!

[professorred]

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 ...

[kmpres]

Very interesting indeed! I wonder if you can tell me how to do this with an FM radio. I live in Tokyo and would like to hear Tokyo FM broadcasts on my Bose Lifestyle 30 stereo(American band) but can't because the Japanese FM band is from 80 to 88 MHz and the American FM band is from 88 to 108 MHz.. Is there a way to adjust the band down in my stereo?