Justin McAllister’s Simple, Post-Apocalypse-Friendly Antennas

Watch Justin McAllister’s presentation on simple antennas suitable for a zombie apocalypse and two things will happen: you’ll be reminded that everything antennas do is amazing, and their reputation for being a black magic art will fade dramatically. Justin really knows his stuff; there is no dangle-a-wire-and-hope-for-the-best in his examples. He demonstrates that it’s possible to communicate over remarkable distances with nothing more than an off-the-shelf radio, battery pack, and an antenna of simple design.

A Hacker-Friendly Presentation

What’s great is that his talk presents information in a hacker-friendly way. Justin knows perfectly well that hackers will go out and dig up information on whatever interests them all on their own, so he focuses on showing what’s possible, what’s out there, and what stuff is called so the audience understands what to look for when they seek out more detail. After all, it can be hard to research something when one doesn’t know the right terms, or lacks an overall understanding.

DIY magnetic loop antenna picked up stations all the way out to Japan, “[…] and this wasn’t on a tower outside my house or anything, this was sitting on my kitchen table.”
The “surviving a zombie apocalypse” angle provides a useful context for the kind of antennas and wireless communications Justin dives into. Post-disaster survival depends in part on knowing one’s environment and communicating with (and watching out for) other humans. It will be important to hear news and be able to communicate with other people. Even if talking with other humans isn’t a factor, he reminds us that things like weather satellites will still be transmitting useful data regardless of what has happened on the ground.

Radio communications can operate without a wider infrastructure to support them, but using it effectively requires antennas, and antennas require their own kind of knowledge. Justin covers the basics of radios, cabling, and connectors in a concise way but focuses mostly on DIY antenna designs, all of which he has personally built and tested. Most of them are perfectly accessible to hobbyists with hardware store parts.

Simple, Effective Designs

Examples begin with simple wire dipole antennas (easily capable of cross-country communications with the right setup) and progress to more complex designs like a magnetic loop antenna, which was able to pick up stations all the way out in Japan from Justin’s kitchen table. Other examples include a dual-band VHF/UHF antenna that can be built with simple hardware, and a three-element Hex Beam antenna made with about $20 of hardware store parts. The last antenna shown is a multiband Vivaldi antenna on a PCB, which can’t really be done with basic hardware, but is nevertheless of simple design.

Wrapping up the talk (at 22:58), Justin shares useful resources for further learning, and warns that “[there are] a lot of opinions about antennas in the world, and a lot of them are wrong.” He suggests sticking to sites and resources that focus on hard data and experimentation.

If you’ve ever wondered what makes antennas work, or how the cable connecting a radio to the antenna (the feedline) doesn’t become part of the antenna, take twenty or so minutes to watch Justin’s presentation and come away with a much clearer idea of how even a self-contained, battery-operated radio can communicate cross-country with the right antenna.

10 thoughts on “Justin McAllister’s Simple, Post-Apocalypse-Friendly Antennas

  1. “Even if talking with other humans isn’t a factor, he reminds us that things like weather satellites will still be transmitting useful data regardless of what has happened on the ground.”

    WWIII. Then after that, sticks and stones.

  2. The problems with the infamous $20 simple antennas are usually (1) feedline and (2) connectors. You can make antennas out of all kinds of clever and re-purposed materials but you normally need feedline and connectors to put them into use. And sadly this gets worse as the frequency goes up and the physical size of the antenna goes down.

    You can make all kinds of really cool wifi antennas for next to nothing, as they are physically small and do not use a lot of materials. The fly in the ointment is low loss feedline for wifi frequencies is expensive as are the “dongles”, adapters that go from the (r)sma or whatever you have on your device, to a larger, lower cost connector you are likely to terminate your antenna into,

    Bigger antennas the feedline and connectors are not as bad cost wise, but you need a lot more materials to make the antenna.

    You are not going to be building a 15 element 160 meter yagi for $20. (smile)

    1. “You are not going to be building a 15 element 160 meter yagi for $20. (smile)”

      Technically peaking Reg…. IN a Z Apoc Money isnt going to be an issue so as that technical aspect bub, 20 turns into 0. So yeh I will be making it, for free no cost tome other than time and little effort in scavenging items to make it.
      If I survive the bandits and the dead… and dont get robbed in the process. ;P

  3. A vivaldi can be made with basic hardware. Just copper or alu tape and a bit of coax. For bigger antennas you can use a tapered gap between 2 wires(instead of metal sheets). Like all antennas it really helps to have good test gear to optimise it, but the Vivaldi is fairly tolerant. Much more tolerant than a yagi for instance that needs to be constructed with some precision.

  4. Even simpler: old modified DVDs can be used to make a primitive dish antenna eg for SETI. You don’t even need to have a rigid dish as simple woodwork can be enough.
    All you need to do is loosely interconnect the edges in at least 2 places and this will work.
    You lose a bit of signal but its minor, especially at >100 MHz.
    You can also make a Yagi clone in this way using offsets and suchlike simply by adjusting the relative angle of each disk and a cantenna-like arrangement is also feasible with a large cardboard tube covered in tinfoil with indium/tin solder from dead laptop heatsink assemblies.

    Note that a good workaround for corrosion is to Epoxy dot the thing once its all tested and working.

    1. But that doesn’t seem to be how it works in the “real” world. There, the more enlightened people are, the MORE they seem to believe in the ZA. Or at least, claim that they do. It might be like Christianity, that way.

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