Make a radio using simple supplies

Tuesday, December 18th, 2018

I’m a bit shocked that I hadn’t stumbled across How to Invent Everything: A Survival Guide for the Stranded Time Traveler until just now, while reading about how building a radio transmitter is easier than building a clock:

Historically, humans were able to navigate with two instruments: a sextant and a clock. A sextant is used to measure the altitude of the celestial north pole so you can determine your latitude. The clock is needed to measure the difference between local noon and Greenwich Mean Time so you can get your longitude. Yes, that’s really how it works — here are the details if you are interested.

But how would you build these on your own? The sextant is pretty simple — it’s just a tool for measuring angles. The clock on the other hand, that’s not so easy. I don’t think I could build an accurate clock from scratch even if I knew exactly how it works (it’s not that difficult conceptually).

If the clock is so difficult to make, then don’t make it — that is the idea from Ryan North, and it’s brilliant. Instead he suggests that it would be easier to make a radio and use that for navigation. If you can build a radio transmitter, you won’t need a clock. The key part of using a clock for navigation is to know the difference between local noon (when the Sun is at its highest point) and noon in Greenwich (or any other reference location). If you have a radio, you can just broadcast the time from Greenwich and compare that to your local time. Boom. You just found out where you are. You didn’t even need to wind up a pocket watch.

Now you are thinking — but isn’t a radio even more complicated than a clock? Nope. The clock needs precision and accuracy in the building process. If you understand physics, you can make a crude radio, no problem. That’s exactly what I’m going to do. I’m going to make a radio using just the simplest supplies I can find.

Of course there are some prerequisites. If you are stuck in the past, you are going to need to “invent” some other things first. Here’s what you need (none of these are terribly difficult).

  • Copper wire. I guess it doesn’t have to be copper, but you will need some metal wire. This shouldn’t be too difficult once you get a good forge going.
  • A battery. If you have two different types of metals and an acid, you can make a battery. It’s that easy. In fact, you can even make a battery from several pennies—here’s how.
  • A ferromagnetic material like iron.
  • A radio receiver. I know this seems like cheating, but it’s not that difficult to build. Here is how you can make one. There are other ways to do this that might be easier, but the bottom line is it’s possible to make one.

That’s pretty much all you need. Even a stranded time traveler could eventually figure out these things.


  1. Buckethead says:

    I’ve been aware of that book for some time, but haven’t read it yet. North is the writer/creator of Dinosaur Comics, which is often amusing.

    Apparently he created choose your own adventure versions of Hamlet and Romeo and Juliet.

    I’ll have to add this one to my list.

  2. Buckethead says:

    Actually, I was mistaken. The book is recent, what I’ve been aware of is the Time Traveller Essentials print/tshirt. This has been around since 2010.

  3. Wan Wei Lin says:

    Easy to do is easy to say.

  4. Adar says:

    The use of a spark gap transmitter is illegal.

  5. Isegoria says:

    He doesn’t literally say that using a spark gap transmitter is illegal, but it does say you shouldn’t do it:

    But be careful. It’s fine for a time traveler stuck in the past to build and use a spark gap transmitter, but they aren’t a good idea anymore. Because of the nature of the spark, this produces radio waves on a broad spectrum of frequencies. That makes it easier to pick up the signal, but it also means that only one person can use this radio at a time. If there were two spark gap transmitters in the same area, you could only hear the more powerful one. Still, it’s better and easier than making a clock.

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