Dust Off Those AM Radios, There’s Something Good On!

If you are into vintage electronics or restoring antique radio equipment you may be very disappointed with the content offerings on AM broadcast radio these days. Fortunately there is a way to get around this: build your own short-range AM broadcast station and transmit curated content to your radios (and possibly your neighbors). There are several options for creating your own short-range AM broadcast station, and this gives you something fun to tune into with your vintage radio gear.

Antique Radios See Daily Use Once More

We see a ton of antique radios turned into Internet radios. Perhaps this is fine if the internals are beyond saving, but what about great old AM radios which still work? Pull them out and try your hand at vintage repair because you’re about to start your own broadcasts that make them relevant once more.

 

The Hard (But Fun) Way: Build Your Own Tube Transmitter

For many audiophiles, you can do no better than a tube amp, so why not take the same stand on your AM transmitter build. You can build your own from scratch using some go-to home AM transmitter designs that have been around for the last 60 or 70 years.

We like Evan’s AM transmitter design which traces its lineage all the way back to a 1939 Zenith model S-7000 Wireless Record Player transmitter. After building the circuit as recommended, he began tweaking the design and ended up with the project box seen above that works with three different tubes.

Phil’s transmitter design, called the Li’l 7, is one you should consider as well. It has extensive documentation, including Bill of Materials (and where to source them!) and assembly instructions. The image we included above is particularly fun; it’s not one of Phil’s but a breadboard version built by a fan of the design.

For a more advanced single-tube AM transmitter you have to check out Robert Weaver’s design which uses a compactron. The compactron is basically 3 tubes crammed into one envelope. These were popularly used as cost-saving devices in later-model vacuum tube television sets.

The Easy Way: Buy an AM Transmitter.

As for me, I have two young children, a demanding job, and not as much time as I used to. I wanted something that would work straight out of the box. I also wanted decent quality modulation so I didn’t want to use a grid modulated AM transmitter. Given these requirements I settled on the Spitfire.

Spitfire’s output is only 100mW into a very short inefficient antenna. I’ve found that by adding more wire you can significantly increase the range. I’m sure that if a really long wire were used you could cover your entire block, but not much further.

You need not be limited to my suggestion, other AM transmitter options include the SSTRAN, and the ‘talking house‘. Grab an old phone, iPod, or even a reel to reel as your music source; anything with a headphone jack that plays audio will do. I looked around and found this inexpensive bare-board MP3 player on eBay and simply glued it to the top of the box.

Be the DJ

Most of the fun in this is actually locating and loading up unique content, putting it in the right sequence — you know, being an AM radio DJ!

My preference is for pre-1950’s jazz and swing music, so I loaded my playlist accordingly. But this wasn’t enough, after some digging I found numerous WW2 news bulletins from the front as well as recordings of music programs.  I also found these vintage commercials which can be fun to sprinkle into your playlist.

There are also some excellent recordings of pirate AM broadcasts available online. One called ‘Grosse Pointe Gardens’ is my favorite. It is basically an entire quasi-live jazz concert broadcast by someone out of his basement from a suburb of Detroit. The quality and creativity are absolutely amazing. It sounds as if a pre-war radio program bounced off a large cloud of interstellar dust back to earth many light years later. You can have a listen here and even download the file to add to your short-range AM radio station’s playlist.

Dust Off Those AM Radios, There’s Something Good On!

Below is a demo of my short-range AM transmitter operating a pre-war battery set, a mid-century Telefunken tabletop radio, and two WW2 military radios. I didn’t build my own transmitter, but I’m having a lot of fun and I may take on one of those transmitter designs as a future project. For now, I’m happy to tune into something that I want to hear on myAM dial!

50 thoughts on “Dust Off Those AM Radios, There’s Something Good On!

  1. The Lil’7 works, but just barely :) I’ve built two of them for folks with old AM radios, the performance is not great. Replacing the coil with a hand-wound coil on about a 1″ form helped a lot (from memory, it was a 25T:75T air transformer, I may be remembering that incorrectly).

    There was a design out there known simply as “Syl’s transmitter,” as the person who designed it went by Syl. I can’t seem to find the original writeup (in French and English). It used a single tube containing a high-mu triode and a power element — I don’t remember if it was a pentode or triode.

    1. That’s only partially true, Michael. If operating under FCC Part 15.209 the only limitation is the allowed field strength emitted from the transmitter in accordance to the formula contained within that particular regulation. Under FCC Part 15.219(b) there is the limit of 3 meters (approx 9.84 feet) for a combined length of antenna lead AND ground lead, if used.

      1. As I am sure Bill already knows, the field strength allowed under 15.209 is not only hard to measure for the hobbyist, it doesn’t give you as much transmit range as operating under 15.219 does. BTW, I’ve passed muster with an FCC agent while operating under 15.219 several years ago.

      1. [audio src="https://archive.org/details/OrsonWelles-MercuryTheater-1938Recordings/MercuryTheater38-10-30WarOfTheWorlds.mp3" /]

        I believe that there must have been only one surviving transcription disk recording of this famous broadcast, as every copy that I have ever heard has the exact same noise at the beginning.

        Now, if I could only find recordings of the radio shows that Fats Waller stared in. Sadly, I believe that none survived, as was the fate of many radio programs.

  2. Am I totally missing the point here? What’s the point? Why make your own radio station? Is it just to show off the vintage radio you inherited or bought from flea market? Instead of using high quality $10 bluetooth speaker? While we are it, why AM when FM transmitters can be found for $10 or less?

    BTW, what’s the Stereo sign about on the AM radio?

    1. Did you forget you’re on Hack-a-Day?

      Why NOT make your own radio station? Fun experiment for someone who hasn’t made an AM transmitter, and who might have a vintage AM receiver lying around.

    2. That’s “AM radio” you are referring to a multi band radio and includes the FM broadcast band. So that’s likely what the Stereo label refers to. That radio isn not old enough to have included C-QUAM AM stereo support.

    3. The point is to be able to use vintage radios, a large proportion of which only have AM. As the selection of AM programming has deteriorated over the years, the only way to listen to decent content is to transmit your own. As to why anyone, including myself, would want to listen to an old radio, it is just one of those things. Same reason as people drive antique cars, it is nostalgia. We fix them and use them.
      As for the stereo sign on the radio, the FM on that radio might be stereo. In any case, the radio will have an input for a turntable that could have a stereo cartridge.

    4. I suppose the same could be said for cooking. Why bother when you can bring home takeout? Or why wash clothes when you can just buy new ones? There’s a distinctive sound and charm in an old tube radio that you don’t get out of a Chinese plastic $10 Bluetooth speaker.

      Unless I’m mistaken, that radio at the end of the video is a 1962 Telefunken that had FM Stereo as one of its modes. It was quite the cat’s pajamas in the day. The AM is clearly not stereo, although there were some attempts at AM stereo a decade or two later.

      1. Well said Sir. I think that Telefunken radio looks a lot like the Grundig Majestic set I grew up with listening in the early 1960’s as a kid. I believe our set also had short wave capability as well. I loved the sound of that thing.

    5. Some people collect old radios. And there’s a lot less to hear, with music mostly gone from the AM band, and so much syndicated programming. At night, the AM band comes alive, endless stations, but not much diversity in programming.

      The collectors like to show off their radios, but for some or many, the programming is lacking. The radios are real radios, so you want to show that, hence the transmitter. If you just feed into the audio system, you aren’t really showing off the radio.

      There are people who collect old tv sets. Generally older sets, or at least ones that have something o make them stand out. But once analog tv was phased out, thy no longer had signals to show off the sets. Some were certainly talking about building low power tv transmitters so they’d have something to watch on the old sets.

      I have a windup radio that tunes the analog tv frequencies. So I could hear the audio local tv stations. But once analog tv was gone, that tv band was completely useless.

      Michael

    6. The point is, “because you can”. My own journey started with collecting OTR (Old Time Radio) programs by mailing CD’s full of MP3’s around (now it is all done via downloads). Later, I thought, “wouldn’t it be cool to listen to these old radio programs on an actual old tube radio”? So, I bought a 1932 Philco cathedral radio and restored it (which led to many more radios later). Now, I needed an AM transmitter. After researching what was available at the time, I bought a SSTRAN kit. Now that I was enjoying broadcasting my OTR collection to myself, I thought, “why not share the fun”? That’s when I bought a second SSTRAN kit, built an antenna, and setup a radio automation system to broadcast 24/7. Yeah, sometimes one hobby gets out of hand and leads to another hobby, and another :-)

  3. Build? Buy a CATV modulator, analogue of course. I picked up a Blonder-Tongue AM-550 for peanuts on eBay. Visions of an amateur TV station vanished because I’m too close to an air Base. Still, fun to play with with a bad antenna to limit my range.

  4. Quickest way to transmit analogue tv signals short range is simply to connect a regular antena amplifier to the rf out of say an old vcr, perhaps having a cctv camera attached via s-video for example. Most will even allow you to set the rf channel. It will be able to be received by an analogue tv in the vicinity with reasonable picture quality.

    1. good stuff .. thnx … ( in regards the radios ..i guess it is easier to get xiaomi roidmi for 10 bucks and with that you can transmit on fm via bluetooth and control the frequency too )

  5. Plenty of radio enthusiasts use legal, license-free Part 15 radio broadcasting to transmit programming to their restored antique radio collections. A growing number of broadcast hobbyists also use unlicensed but legal Part 15 radio to entertain their local neighbors with hyperlocal radio. Colleges, universities and K-12 schools have been using this technology to teach broadcasting and related subjects such as media production and journalism. Many of these same educational stations serve as an extracurricular activity for the student population. Those versed in electronics can build their own transmitters though there are a variety of manufactured, FCC certified transmitters available for purchase.

  6. FYI, SSTRAN is not accepting new orders.

    As for why one would want to transmit to a tube radio rather than use a modern Bluetooth speaker, some prefer the sound of a tube radio.

  7. The modulation ad-on that made AM into stereo was better than what made FM into stereo. Until we lost WBAA AM920 as a HiFi radio mono station it hardly mattered that we didn’t have an FM source for NPR. Virtually no static in town during T-storms. Years later they finally got a LPFM replacement, though it is stereo it’s noisy and raspy.

    Anyone that that is not aware of the degradation of the blurtooth scheme need not comment on weather an old Zenith can sound better. Blurtooth sounds like bad AM not tuned in right. It is unfortunate that volume crushers have taken over even our local high school oldies station. I had to delete the preset.

    For years I had a one tube AM transmitter that a friend built from one of the hobby zines in the mid “60”s, it was fun. But I never messed with it much after then. I have had micropower FM going for years. Which brings us to the convenience of listening to anything on a kitchen, basement, garage, or headphone radio. AM or FM the choice is yours.

    1. Yes, that sort of project was common in “the old days”. About 1971 I’d take a Rufus P. Turner book from the late fifties out of the library, loads of projects, mostly tubes but some transistors. I never built anything from it, but it was exciting at the time. Decades later I found the book at a used book sale.

      A variant was “wired wireless”. It used low radio frequencies, but coupled to the AC line rather than a transmitter. So you had to couple the receiver to the AC line, so less chance of the signal getting away. It was used by university “broadcast stations” among others, there was a “Carl & Jerry” story about it.

      Michael

  8. I wonder if there is text to speech yet that can sound like a real person, and more specifically like a 50’s newsreader.
    If so you could make it read out trump tweets or something.

  9. It is a shame that the excellent SSTRAN AM kit is no longer available. I had purchased two of them some years ago, when I was into restoring old tube radios. I had the circuit board from a SSTRAN transmitter mounted into a weatherproof box, along with a homemade base-loaded antenna. I used to get up to one mile transmit radius. I used a spare PC and the free version of ZaraRadio https://www.zarastudio.es/ to play from my OTR collection 24/7. I wasn’t into playing DJ myself, so automating things with ZaraRadio was the way to go. It was lots of fun. I had more than one AM tube radio to listen on, but my favorite was a 1947 Delco table radio that had exceptionally good sound.

  10. Another comment, related to AM broadcasting (in the US): if you read FCC Part 15, there is a section that covers carrier current broadcasting. The wording is confusing, because it starts out talking about campus operation. However, a closer reading of the rules indicates that carrier current operation is not restricted to college campuses and the like. In fact, any individual can operate a carrier current station. There are a few individually operated carrier current stations across the US. I thought about setting up a station myself, but at the time, it was not feasable. Depending on how your electric grid is setup, you might cover a small town, or only down the street. The only way to find out is to try it. With carrier current, you are using the AC line to carry your signal. The receiver needs to be either be plugged into the AC line, or very close to it to pickup your broadcast signal. Final thoughts: Don’t electrocute yourself. Read up on carrier current and especially line couplers.

    1. Carrier current is interesting.
      I have a 27MHz carrier current line coupler in my junk box. It’s made for 27MHz paging.
      Paid whole 2euros for it at a hamfest.
      It is likely going to find a new life rebuilt as a QRP HF antenna tuner.

  11. Interesting video. Love the scenes from Metropolis, one of my all time favorite movies. Probably explains why fondness for old time radio. I have never owned an MP3 or other player-on-a-chip device, never bought a music CD, 8-track or vinyl disc, and to this day have never downloaded an iTunes song. My smartphones and computers are capable of playing digital tunes but I don’t even bother with that. Somehow I just don’t miss them. I do, however, love that old tube radio sound and the songs of the Jazz Era through the 1960s – not the raucous “stuff” or “talk radio” passing for AM programming these days. Been searching for a good tube based AM transmitter design for some time that I could build to transmit to the antique tube radios that I like to restore as a hobby. It would have to be one capable of transmitting enough bandwidth to accurately test those radios as well as reproduce the true Hi-Fi mono AM sound people used to receive on the high-end and very expensive radios of the 1930s and 40s. FM was around back then but it didn’t become a broadcast medium until the mid 1950s. A transistor based TX, even a good one, therefore just doesn’t cut it. So, I thank you for this post! Hopefully one of the above tube designs will serve my needs nicely. Might even buy my first MP3 player to serve as input for the TX. Then I could be my own old time network broadcaster and listener at the same time…

  12. Anyone know of any similarly priced pre-built models available, similar to the Spitfire and Talking House models referenced in the article? I want to set up a transmitter, and just wondering if anyone has any experience with any other models.

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