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.
Listening to shortwave radio is one of many reasons I got my amateur radio license. sounds like you would enjoy it
Thank you. I thought seriously about it a couple of times. A college roommate had his Heathkit rig set up on his desk with a dipole antenna strung above on the roof. It was chilly in the room when he connected the dangling antenna coax through the cracked sliding window during a Minnesota winter. I really liked the electronic theory, but never got very far learning code. I know there is a no-code license now. At this point in life I have too many other things happening.
<p>Very informative instructable. My uncle showed me something very similar many years ago that I then tried myself. His method instead of winding wire over the coil on the ferrite rod, he would use a lighter to heat up the rod and burn off some of the insulation on the wire wrapped around the rod and then he would separate the wire so there was spaces in it.</p><p>This got me interested in listening to Shortwave radio and I spent quite a bit of my teenaged years listening and sending QSL radio reports in to the stations I heard on a Radio Shack Shortwave radio I got one year for Christmas that had a great digital frequency display. I got more than a few QSL cards back from the stations and some would send cool stickers, pennants,etc. I think before I finally got bored with it I had over 100 different cards. I'll have to check the closets at my Mom's house and see if she still has my photo album that I put my QSL cards into.</p>
very cool . i must try this , thank you for sharing
As you can see from the other comments, several others tried it and found it to work. Thank you for looking and for commenting.
<p>This is such an excited find! I cant wait to try this at home! </p>
<p>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!</p>
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.
<p>Do the new wraps need to be in the same direction around the ferrite as the original factory coil?</p><p>Do the new wraps extend the coil in a serial connection or parallel it?</p>
I paid no conscious attention to the direction of the windings relative to those already on the ferrite coil. The windings are in parallel.
<p>Cool project. I'm going to try this one. Thanks!</p>
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?
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. <br><br>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. <br><br>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.<br><br>Thank you for your comment and for looking. I hope you and your kids find enjoyment and success in your efforts.
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. <br><br>I think I will do this with an old AM radio I have. Thanks for the memory.
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.<br><br>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. <br><br>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.
If you go to this <a href="http://www.bing.com/images/search?q=zenith+floor+radio&view=detail&id=426FBE95EFC7C948772ADA9FDA4F89DFBFFB601D&first=0" rel="nofollow">link</a>, 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.
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: &quot;Get off the line you damn yankee!&quot;
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. :)
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.<br />
I do not know enough about car radios to say if it is possible.&nbsp; You can, however, order a shortwave converter for your car radio.&nbsp; Here is <a href="http://www.angelfire.com/ia/lfb/" rel="nofollow">one link.</a>&nbsp; But, it is not cheap--about $165.&nbsp; <br />
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&nbsp;Morse&nbsp;code.
It should do that for you.&nbsp; This makes an interesting receiver.&nbsp; But, it is not always a great receiver.&nbsp; I hope it does what you need.<br />
&nbsp;If I can find it that is.&nbsp;
I used to get SW&nbsp;stations back in 1991 with a cheap $20 radio, but the radio fell apart, but I have kept in touch with the world. &nbsp; The radio was a portable Windsor TV/AM/FM/Weather radio.&nbsp;&nbsp; I&nbsp;also had a friend that was picking up shortwave broadcasts on his AM/FM&nbsp;clock radio until I&nbsp;told him to put the ferrite rod back in place. &nbsp; It was a new come back experience. &nbsp;&nbsp; Now I&nbsp;feel I&nbsp;might experiment again. <br />
Thank you for trying this modification and reporting back that it worked for you.&nbsp; 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.&nbsp; Your friend's experience with the presence or absence of the ferrite rod on his clock radio is interesting.&nbsp; The early 1990s was the height of my shortwave listening experiences.&nbsp; The number of stations I am able to receive currently is only a shadow of what was available 20 years ago.&nbsp; But, I now download Podcasts from some of those same stations and convert them to CDs I can play in my car.&nbsp; My aim was to improve at understanding spoken German.&nbsp; Although I miss the shortwave broadcasts, the audio quality on the Podcasts is far superior to anything I ever heard on shortwave. &nbsp; (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!)&nbsp; &nbsp; <br />
I tried it,&nbsp; it works very good, except it drifts alot, it takes patience to tune and experimentation.&nbsp; I also used one of my indoor shortwave radio antennas.&nbsp;&nbsp;&nbsp; What a great way to get access to world band on a radio you do not use.&nbsp; Great Job!&nbsp;&nbsp;<br />
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 <a rel="nofollow" href="http://my.integritynet.com.au/purdic/am_rec.htm">http://my.integritynet.com.au/purdic/am_rec.htm</a> . 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 <a rel="nofollow" href="http://www.tpub.com/content/neets/http://www.tpub.com/content/neets/">http://www.tpub.com/content/neets/http://www.tpub.com/content/neets/</a> 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.<br/>
Came back to get an url I failed to bookmark, and notice errors in my post, Exclamation deleted.<br/><br/>Read the USN training docs here <a rel="nofollow" href="http://www.tpub.com/neets/">http://www.tpub.com/neets/</a><br/>Download them here <a rel="nofollow" href="http://www.tech-systems-labs.com/navy.htm">http://www.tech-systems-labs.com/navy.htm</a><br/>
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?
Perhaps some of those with a background in engineering or amateur radio can tell you. Shifting the FM background is way beyond my knowledge.
Essentially, you can't. Frequency Modulation (FM) radios pick up signals which carry the data (audio) by shifting the frequency (number of cycles per second) of a carrier wave. Amplitude Modulation (AM) radios work by shifting the amplitude (amount of power) being pushed in to a carrier wave. Shortwave radios are just AM radios that operate on a different frequency range; however, FM radios work on an entirely different technology (If you were to graph it, AM radios measure vertical change and FM radios measure horizontal changes in the periodicity of a carrier wave (which, unmodulated, is a sin wave). /nerd mode off
Quite right, thank you for that well thought out response. I can't help thinking, however, that the only difference between an American FM receiver and a Japanese one is a 10 to 20 MHz shift in carrier frequency. Is there a way to add, say, 10 MHz to an incoming Japanese FM signal and thus fake out the front end of an American FM receiver into thinking that it was getting a carrier within its designed range? You'd, in effect, fit the Japanese band inside the American band which is twice as wide. I imagine a kind of frequency adder circuit or "pre-tuner" would be necessary. There are easier ways to do this, not the least of which is to simply buy a Japanese tuner and use the AUX port, but why waste the chance to take apart a $2,000 stereo and with a handful of parts, make it work better than before? (This is the price of nerddom.....;-)
Sorry, I misread your original post -- I thought you were talking about changing an AM radio to receive FM signals, or vice versa.<br/><br/>If your FM reciever circuit is relatively simple (a one-transistor type), you could probably achieve the result you want by swapping out two capacitors -- essentially, one determines the low end of the signal range and the other determines the &quot;band spread&quot; (i.e. sensitive range). Here's an article with diagrams showing what I mean:<br/><br/><a rel="nofollow" href="http://www.vk2zay.net/article/129">http://www.vk2zay.net/article/129</a><br/><br/>I wouldn't want to recommend screwing around with it too much though -- if you swap the wrong caps, you run the risk of completely frying your (apparently very expensive) radio. I'd also like to add a caveat: Although I'm an amateur radio enthusiast (as of yet just theory, although I hope to get licensed soon), I have never built a radio more complicated than a simple crystal receiver, so I could be completely off base.<br/>
do you know how to convert from a 49 MHz radio to a 27-MHz radio?
Actually there is no "ideal" with these kind of modifications. That means securing the mods is really advised, unless operating conditions warrant it. you may need to go back to adjusts the turn spacing ot even use another coil with more, maybe less turns
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?
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.
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.
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 ?
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?
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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Bio: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying ... More »
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