Steam Tech : Transmitting Radio Without Tubes

One thing hard to reconcile in Steampunk is either a lack of wireless communication. Of course Babbage is served by Radio Riel.

Now no one believes that Marconi invented radio. Thats pretty much disproven, but he did demonstrate a very workable long distance wireless telegraphy setup, and it would be a few more years before the first vacuum tubes,( Audions, valves, what have you) led to the modern circuits we now use for, well, everything.

I have a fascination with very early radio, so I thought I’d show some of the methods that WERE used, and what also might have been used with the technology of the times, if it had been chanced upon.

Of course most early radio involved spark-gap. This is a really simple method. Antenna, coil, DC source, ground. It’s an extremely sloppy way to transmit, of course, but it worked. It must be remembered that the telegraph keys used were actually keying the full voltage. One can imagine you had to be careful.

this is the spark gap transmitter at the ARRL museum in Connecticut. I took one of my daughters there. This one actually employed a rotary spark, gap, I believe.

Attempts were made with various success to modulate the spark gap with a carbon microphone as well. This couldn’t have been easily to discern, and the idea of talking close to that much current in a live (probably water-cooled) cabon microphone is disconcerting. But we’re not done yet, because things are about to get stranger:

 

Whereas the spark gap was basically puting out a wide pattern of static slightly louder than the background noise, a true carrier wave would be needed for efficient long distance and voice. Enter the Poulsen Arc. The more you read about a Poulsen Arc (invented by a man who invented magnetic recording at the turn of the last century!) there just seems to be something vaguely mad-science about it.

The arc still remained, but now this same electrical arc was continuous, and it oscillated. Oscillated? Oh yes, by dripping something flammable into it (usually alcohol, but sometimes Kerosene, if radio operators found their supply of alcohol wandering out of the radio room), and then modulating this flaming arc with magnetic fields. This gives you the ability to produce true AM transmissions, or Continuous Wave (CW) telegraphy. Even though it was invented in 1906 or so, there’s something VERY steampunk-ish about the Poulsen Arc, and I suspect that if it we did have a fantastical 19th century filled with calulating engines and mad scientists in airships, the device would have been invented sooner. Sadly, it is all but forgotten now, and very few examples remain.

 

But for fans of Tesla, well I have no Tesla. Someone was bound to bring up Tesla, but I won’t, damnit. They ALWAYS bring up Tesla. Anyway, if you like Tesla, you’ll love the Alexanderson Alternator. This is radio’s “Big Honking Machine.” This is what you operate when you want a nice Longwave signal that will ride the earth and each your target audience, in whatever continent they happen to be in. Without getting into the theory of it too much, it used two rotating coils and an amplified magnetic field. Two REALLY BIG HONKING coils. As a longwave transmitter, it required great power, and antenna farms reaching for miles, and stations of this sort were few.

Unlike the Poulson Arc, there is still one Alexanderson Alternator which is operable, out of Gremeton, Sweden (image below). Every decade or so, they appear to turn it on for special events and broadcast. While I know of no currently made commercial radios that will actually receive at the low frequences of the Grimeton station, your computer’s sound card will naturally receive the audio, and I believe there is at least one free program to turn your computer into a VLF receiver for the purpose. It’s also fun to listen to echos of lightening around the world. I digress.

(drool).

 

But imagine a past-that-never-was, where dashing personages in their small boats, homes, and airships needed a more compact method of close communication, and yet, dash it all, no one had yet invented the Audion tube. Help is on the way.

While a few people have probably accidentally encountered the Zinc Negative resistance oscillator over time, it’s a pity that no one found it at the “right time.” For by the time anyone thought to try working with it as a solid state semiconductor, better devices already existed. A piece of zinc treated steel would have done the trick. Now, it’s more of a curiosity, but its interesting to see what can/could have been done:

http://home.earthlink.net/~lenyr/zincosc.htm

http://www.youtube.com/watch?v=uLYQgrFPB3k

 

Hope this was of some interest.