Mad Science: Tesla's Radio

They said I was mad! Mad, I tell you! But soon I shall show them all, bwahahahaha!
The weird looking contraption in the picture above? I built it, and it works, and you can listen to it a few paragraphs down. But first, some backstory!

There's a good chance you were taught that a man named Marconi invented the device we call the radio, and that his patent was issued in 1904, ushering in the age of the wireless and kicking off the gadget-happy 20th century in grand style.

It's a good story, but it's also a big fat lie. The truth is this -- Marconi's financial backers, Thomas Edison and Andrew Carnegie, slipped the American Patent Office an undisclosed sum of cash, and the owners of the original radio patent found their patent revoked. I can only assume these unfortunate fellows were notified via mail, in a letter which stated 'Sorry, but wow that was a LOT of money.'

But if you dig a little deeper, you'll find that a Serbian genius named Nikola Tesla had the whole lot of radio experimenters beat, because he was sitting up late nights in his laboratory near Pike's Peak and freaking himself out with the radio he built before the rest of the gang ever gazed longingly at a chunk of germanium and wondered if they could drag voices from  it.

Rocking that 'stache like a boss.
Let's set the scene in Tesla's laboratory, which did indeed look like the set from the original Frankenstein movie. The place was littered with massive Tesla coils, some of which could throw sparks over a hundred feet. There were electric motors spinning and sparking, AC transformers humming, gears and pulleys turning away. If you think I'm exaggerating, consider this -- residents of the nearby town knew when Tesla was at work when sparks reached from the soles of their shoes down to the street every time they took a step. The blue glow that surrounded Tesla's tower was visible from town.

Nikola Tesla wasn't screwing around. He invented the electric motors still in use today. AC power? That's his. So are a dozen other commonplace bits of technical wizardry. The man would build machines in his head, watch them fail, make mental improvements until he'd worked the bugs out. Only then would be set about constructing the actual device. He was that good.

So, late one night in 1893, he fired up the radio set he casually conceived and listened, curious as to what he might hear.

What he heard astounded him. Frightened him, even. He became convinced that he was picking up some form of communication between entities unknown.

You can read his own recounting of his first exposure to radio in this 1901 article Tesla wrote for Collier's Magazine.

Talking With the Planets by Nikola Tesla

In the article, Tesla (correctly) decides radio is the best way to communicate over long distances. I doubt he foresaw radio's use as a way to sell laundry detergent, but nobody's perfect.

Of his first experiences with radio, Tesla says this:

"I can never forget the first sensations I experienced when it dawned upon me that I had observed something possibly of incalculable consequences to mankind. I felt as though I were present at the birth of a new knowledge or the revelation of a great truth. Even now, at times, I can vividly recall the incident, and see my apparatus as though it were actually before me. My first observations positively terrified me, as there was present in them something mysterious, not to say supernatural, and I was alone in my laboratory at night; but at that time the idea of these disturbances being intelligently controlled signals did not yet present itself to me."

--Collier's Weekly, February 19, 1901

All of which begs the question -- what did Nikola Tesla hear, that night so long ago?

He couldn't have heard commercial radio signals, because there weren't any. Distant lightning, sure, as a burst of static. The usual hissing of the cosmos, which extends all the way down to the AM band.

But nothing I could think of would present itself as voices, or attempts at communication.

Given the materials Tesla had on hand at the time, his radio set was almost certainly a chunk of germanium (or a similar crystalline mineral) and a crude arrangements of inductors, resistors, and capacitors.

Luckily, all those things are easily obtained today. What Tesla was listening to was what we call, with a hint of nostalgia, a crystal radio set. It uses no power, save for the tiny amount collected by the antenna itself. At the heart of the radio set is a tiny hunk of germanium, which is found in the center of a thing called a 'germanium diode' which runs you a whopping 49 cents from most electronic suppliers.

I built my Tesla radio based on the set found at the end of this link:

Spooky Telsa Radio on Instructables

As you can see, his radio set is prettier than mine, but mine is a better card player, so there.

If you listen to the audio samples from the Instructables page, you'll find that lightning strikes sound just like thunder. Keep in mind the output of the Instructables set is being modified with audio processing software before you hear it -- reverb and other effects are being added to make it sound cool. Which is fine, but I prefer to record nothing but the raw audio.


Well, listen to the very brief audio sample below.


Scary, right? Sounded like something out of Satan's own closet of nightmares, didn't it?

That was me, reciting 'Mary Had a Little Lamb.' It took me six mouse clicks in Audacity to render the harmless nursery rhyme into something sinister.

Since Tesla didn't have access to my computer, I won't be adding sound effects to the recordings.

Building the Radio

If you have a mind to build your own crystal radio set, I'll include my own drawings and parts suppliers here. It's really not hard. Or you can buy pre-wired sets from various places around the web.

The Instructables site includes a complete parts list and schematic. I'm including mine because I made a few changes. Also, I didn't draw it out in schematic form, but depicted each component and where the leads should actually connect, in case anyone without electronics experience wants to give this a try.

I got a 1/8 inch mono plug to act as the output. I chose 1/8 inch because I have an old-school high-impedance earpiece with an 1/8 inch plug; I can use that listen to the radio, and a 1/8 inch mono cable to plug the radio into my PC's mic input so I can record the sounds. More about that later.

You can build your rig any way you want to, as long as the proper connections are made. Soldering is involved, but that's easy to learn and soldering irons are cheap. The only thing you need to be careful about is soldering the diode; they're fragile, and heat can quickly destroy them, so don't leave the iron on the leads too long.

I got D1, VC1, L1, R1, and C1 pictured above from the nice people at Scott's Electronic Parts. Below are the parts numbers from Scott's:

D1 - #1N34A-1
VC1 - #Var141-1
L1 - #FAC
C1 - #Cap.001uf-4
R1 - I had a 47K ohm resistor already. The Radio Shack part number is 271-1342
Earpiece - #CerEar-1
Mono plug for 1/8 inch mono cable: Radio Shack part number  274-251
The small amplifier shown in the photos is a Radio Shack part number 277-1008, cost $14.

I had a scrap of oak to use for the base. I got a five by six inch piece of 1/8 clear plexiglass to use as a component mounting board. Four bolts hold the whole thing together.

I wound my hilariously un-circular spiral antennas from 14 gauge copper wire. I would up attaching each spiral to a small sheet of clear plexi because the coils kept flopping around and shorting out. 

Why spiral antennas? Because Tesla's drawing and notes are littered with spirals. The man loved a spiral or two. That's a bit of homage to him, it was a shape I could easily create with six feet of copper wire, and since this project is as much about fun and art as it is about anything else, why not a spiral?

The antennas plug into banana jacks, easily gotten from Radio Shack, and the whole works cost around 30 bucks.

So, the radio was finished. I could hear sounds and voices in my earpiece. It was time to plug one end of the mono cable into the radio, and the other end into my PC's mic input. Which I did. I then fired up Audacity, selected the mic input, and hit record.

Nothing happened. Nothing at all. I was monitoring the input levels, and they were stuck at zero.

I plugged my earpiece in, and heard voices. 

What did that mean?

It meant the radio's output was far to weak to reach mic-level ranges, which start around 0.3 volts. I made a sad face, cranked the gain up within Audacity to ludicrous and stupid levels, and still got nothing.

I asked myself 'What would Tesla do?' and rummaged through my ghost-hunting gear until I found a small portable audio amplifier. I hooked it up to the radio, and it started mumbling in loud angry Spanish, so I knew I was onto something. The little amp has an auxiliary output, so I plugged that into my PC, and like magic, the voices began to speak.

Now, Frank, shut up and tell us how it sounds!

Listening to the Spooky Voices of the Planets

The little radio fired right up, filling my earpiece with a mixture of static, faint voices, and the ever-present 60-cycle hum of modern house wiring. 

By gently turning the knob on the variable capacitor, you can (sort of) tune in on different signals. Now, keep in mind this isn't a commercial radio set. It doesn't actually have what even the cheapest Wal-Mart radio would call a 'tuner section.' Stations come and go, fade in and fade out, pretty much at random. One minute you're getting the local NPR station, the next it's an agitated gentleman speaking in rapid-fire Spanish, and then that gives way to garbled music and what sounds very much like goats bleating.

And that's just during the day. At night, when the ionosphere bounces AM radio signals around like so many meth-crazed tennis balls, things do get weird.

But hey, you've read this long, here's a sample, torn right off the late-night airwaves!

Gotta love that whole Children of the Corn vibe the preacher was giving off. The late-night airwaves of today are a static-flooded wasteland of AM sermonizers, each stranger than the last. I heard one such worthy exhorting the many miraculous blessings of the Magic Hand, which was quick to bestow upon its owners good fortune, improved health, and a joyous love life, Mastercard and VISA gladly accepted for orders, quantities limited, get yours today!

All of which is amusing enough, but what about the sounds that caused a genius such as Nikola Tesla to determine, well before anyone else, that radio would one day be the link between Mars and Earth?

Well, in that regard, I must report my brief explorations have thus far returned nothing. Attempts to 'tune' between active stations are almost impossible -- there are a LOT more AM stations broadcasting than I thought. Too, the range of such stations can vary wildly. I routinely pick up brief transmissions from South America and Mexico, even on this little rig.

The 60-cycle hum is truly annoying. My next recording session will be held outdoors, far from the house, recorded on my ancient Dell netbook. I hope doing so will make any faint signals easier to detect.

So What Did Tesla Hear?

To put my conclusions in esoteric scientific terms, man, I have no idea.

Aside from static in one form or another, I can't image the radio environment of 1893 being very rich in anything but white noise and brief loud cracks of lightning. Was Tesla hearing the workings of his own machines? Was his radio set somehow creating weird sounds as part of a technical malfunction? Was Tesla just pulling our legs because articles about boring old static don't sell many stories to Collier's Magazine?

We may never know. I will keep playing with this radio, though, and if I manage to get Mars on the horn, you'll be the first to hear it!

Writing News

The big event, naturally, the new Markhat release! The new book THE FIVE FACES goes on sale June 17. 

I can tell more than a few people have already put in pre-orders, and for that I thank you!