Tactical Technology for TEOTWAWKI – Part 6, by J.M.

(Continued from Part 5. This concludes the article series.)

Pilot of the Airwaves

Another area where mobile electronics can provide some useful tactical functionality is communications, even if cellular networks and the Internet aren’t available. There are a lot of good articles here on SurvivalBlog.com about radios, so I’m going to focus on other areas.

One very useful option for communications is a goTenna Mesh paired with each mobile device on your team. They’re around $180 a pair, but goTenna frequently has them on sale for 20% or more off. It’s a small device that you clip to the outside of your gear and pair with your mobile device using Bluetooth that allows you to send text messages to other goTenna users. It uses MURS frequencies (151/154MHz) to communicate between goTennas, and all communications are strongly encrypted. They advertise up to a 4 mile range between devices in the open, and I’ve been able to exchange messages with another user over two miles away through broken terrain; there are even stories of people being able to connect over a distance of 25 miles in perfect conditions.

Being able to exchange information via text messaging can be a huge advantage if you need quiet communications in tactical situations, and there’s a lot less chance of your communications being intercepted than with radio. There are also instructions available on how to make your own solar-powered goTenna repeaters, which you could deploy on some high points around your AO to extend your range – the goTennas will ‘hop’ a signal between devices to get it to its intended recipient. Once the goTenna app is installed on your device, no Internet access of any kind is required to communicate with other users. Note that goTenna provides an optional subscription service called goTenna Plus, which allows you to do things like download and use topographic maps to share your location, have messages relayed via cellular service when one user in the mesh has cell service, automatically send your location to someone at a regular interval, etc. These options are pretty nice, but since they require Internet access and GPS so I wouldn’t recommend counting on them in a post-SHTF scenario.

One of the limitations of goTenna is that the MURS frequencies it uses restricts the amount of data that can be transmitted. This is why the app is limited to only sending text messages. There are other app-only options for communicating between mobile devices when the Internet is not present that provide a less expensive solution than goTenna, but most of these utilize Bluetooth and/or WiFi on the device itself, which is going to limit the effective range. The upside is that WiFi and Bluetooth provide much higher data bandwidths, which means you can send things like photos, and files, and even make voice calls. Here are some options:

Some of these apps support WiFi Direct, which involves directly connecting two mobile devices point-to-point via WiFi. Others require a WiFi infrastructure network be present, which you could create using the field WiFi network I mentioned earlier. I’ve played around with several of these and they all have their strengths and weaknesses. If goTenna isn’t a viable option for you or you want the ability to send things like pictures back and forth between mobile devices, I recommend trying out some of these other apps to find one that meets your needs.

Another function that a mobile solution can help out with is the ability to intercept and record radio communications when you’re out in the field. For example, say you’re monitoring an area and you notice some suspicious-looking characters talking to each other on what look like cheap Wally World FRS radios and you’d like to listen in, but you’re carrying Motorola MURS radios for your team, which don’t get FRS frequencies. You can plug a RTL-SDR ($25) dongle into your mobile device using an OTG adapter, hook up an antenna, start the SDR Touch app and start scanning. For those of you that aren’t familiar with it, SDR is Software Defined Radio, and it’s a small device that plugs into a USB port and uses software to perform most of the functions performed by hardware on traditional radios.

With the appropriate antenna it’s capable of receiving radio communications on frequencies between 500 KHz and 1.2 GHz. While originally used on PCs, Macs and Linux computers, some enterprising folks have created an Android app called SDR Touch that allows you to perform most of the same functions that you can on a PC. You will need an OTG adapter to plug it into a mobile device, and I recommend using one that allows you to supply external power so the RTL-SDR isn’t draining your mobile device’s battery.

The antenna you use is going to play a big role in how well you will receive the desired radio signals on your RTL-SDR, and the one I recommend is a Multipurpose Dipole Antenna Kit ($15), made by the same folks that make the RTL-SDR. It’s lightweight and breaks down for easy transport, you can adjust the length of the antennas to optimize for frequencies between 70MHz and 1030MHz, and the base has a standard ¼” screw hole, so you can mount it on the tripod selfie stick I mentioned earlier (hint: bring a small tape measure to get the antenna lengths right). Other portable scanning antenna options include:

If you’re not familiar with the RTL-SDR I highly recommend reading the book ‘The Hobbyist’s Guide to the RTL-SDR: Really Cheap Software Defined Radio’ – it provides a wealth of information on how to use and optimize the device. There are also some other useful apps that can help when you’re scanning – Antenna Tool can help you figure how long your adjustable antennas need to be for a specific frequency, and US Amateur Radio Band Plan which can help you remember what the various radio frequency bands are.

You could also use mobile radio systems like the RTL-SDR for radio direction finding to locate someone transmitting with a radio, but it requires additional equipment and expertise – check out this and this.

Sound Off!

While humans rely heavily on visual cues, sounds can also play an important role in awareness and information gathering when in the field, and there are some electronic technologies that can improve your ability to collect and manage sounds. The first and most obvious are hearing amplifiers like the Walker’s Game Ear and Walker’s Silencer. Both of them amplify available sound, and both provide some protection from loud noises like gunfire. You could also use standard electronic ear muffs, most of which also amplify sound, but they’re kind of big and bulky for regular use. A regular hearing amplifier works to amplify ambient sounds, but most won’t provide very good protection from loud gunshots. The ‘As seen on TV’ SuperEar Personal Sound Amplifiers works surprisingly well, but the downside is that you have to hold it and point it at the sound source you want to amplify, so it’s better suited for listening when you’re staying in one place as opposed to being on the move. An advantage of the SuperEar is that it provides an audio-output jack, so you could pipe the sound into your mobile device or voice recorder and record what you’re listening to. If you want to both listen and record at the same time, you can use an audio splitter to plug in both headphones and a cable for your recorder.

If you want to be able to pick up sounds from a long distance away you’ll need something like a parabolic microphone, which uses a dish to collect and focus sounds. Unfortunately, decent parabolic microphones are bulky and expensive, so they’re not very practical for normal field use. Keep in mind that with parabolic microphones, larger dishes tend to pull in sounds from further away, so bigger is better. A company called Telinga makes a parabolic dish that rolls up for easier transport, but the disk alone costs $200 with shipping. Of course you could always go with one of those kid’s spy microphones, which I’ve never tried, but it’s gotten some surprisingly good reviews on Amazon. If you want to roll your own just search the web for ‘DIY parabolic microphone’ – there are tons of examples available.

Another possible use case for audio equipment would be recording when you’re not present – say for example there’s an abandoned house that looks like it’s being used by squatters, but there’s no one around and you don’t want to set up an observation post to watch it overnight. You can plant one or more tiny voice-activated recorders around the rooms being used, then come back the next day and access what was recorded using your mobile device. Alternatively, you could plant some FM or FRS/GMRS frequency wireless microphones and set up nearby to listen in on what’s being said. I realize that some of this sounds like it’s straight out of a spy novel, but depending on your circumstances and AO it could prove to be useful.

Dammit Jim, I’m a Doctor!

Another area where electronic technology can be leveraged is for medical care – in addition to the medical-related reference apps I mentioned previously, there are several options that can help you diagnose and monitor medical problems in the field. The simplest one is a magnifying app on your mobile device, which provides some limited macro zoom capabilities for your device’s camera. This can be useful for finding splinters, ticks, etc., particularly for those of us with more ‘mature’ vision.

The new generation of inexpensive ‘smart watch’ devices provide the ability to monitor a person’s blood pressure, heart rate, body temperature and blood oxygen level with a single device, and many of them provide a Bluetooth interface which would allow your medic to monitor a person’s vital signs without having to stop and take readings or remove their clothing in cold weather. I’ve used one of these for a couple of months, and most of the readings it provides are surprisingly accurate; the one that always seems to be a few points off is blood pressure, but it’s consistently off so I can easily adjust. One recommendation is to put it on so the sensor is facing the inside of the wrist near where you normally check for a pulse, as this seems to provide the most accurate readings. They also have to be worn for a while (10-15 minutes or so) before they start providing accurate readings for temperature.

An otoscope is a potentially useful medical device – it’s basically a shorter version of an endoscope with a stiff handle on the camera end that plugs into your mobile device. This can be used for looking inside the mouth, ears, etc. to check out problems or wounds. This is probably more useful in your home medical clinic, but it might have some value on longer trips out in the field.

You may also want to consider a portable ultrasound machine. Note that these are expensive (anywhere from $1,300 to $10,000 and up) and require some training and experience to use effectively, but they’re great for checking for broken bones, finding foreign objects in soft tissue, etc. The US military started deploying portable ultrasound machines to their SpecOps medical teams many years ago, with extremely positive results. There are a number of good books and videos on YouTube on how to use ultrasound machines, and yes, I realize that watching some YouTube videos won’t make you a doctor, but you have to start somewhere.

Odds ’n Ends

There are a lot of other miscellaneous technology solutions that can be useful for field situations. One of these is motion detection, which allows you to check for people coming down a trail, or allow a single watch stander to monitor multiple possible approach paths. One motion sensor I’ve used for monitoring possible approach paths during paintball games is battery powered, connects to a WiFi network and sends alerts to your mobile device, so you’ll need to set up a field WiFi network in order to use these. A company called Olymbros makes a very cool outdoor wireless motion detection solution that doesn’t require WiFi – the sensors send alerts directly to a watch you wear. I don’t have any experience with the Olymbros product, but it’s on my wish list. Note that the sensors use 9V batteries, so you’ll need to include a couple of rechargeable ones in your preps.

One thing I’ve done that works well is to stick one of the wireless cameras I discussed earlier on the bottom of a motion sensor, and connect to the camera when I get a motion alert to see what triggered it. A note about motion sensors – since they detect changes in temperature moving across their field of view, one of their biggest issues is that you tend to get false alarms from moving shadows, blowing branches, etc. One thing I’ve done with the ones on my house is to glue a short piece of plastic tube over the round sensors or flat plastic ‘blinders’ to the side of the horizontal ones to limit their field of view, which significantly cuts down on false alarms.

Technology can also help you locate things like hidden caches. I have a couple of the Tile Mate Pros that I attach to various pieces of equipment that tend to walk off around our house, and I’ve got a couple more in my prep kit. Note that the Tiles have a feature called Community Find that allows you to locate things if someone else with the Tile app has passed near it recently, along with the ability to locate something using directional finding with Bluetooth from up to 400’ away (for the Pro). Having other folks potentially know where your caches are located probably isn’t a great idea, so I have a couple of these that I’ve paired with my phone and store in a Faraday Box. I figured they’ll be good for marking caches post-SHTF when cell service and the Internet are gone, using the Bluetooth find feature to precisely locate them. They use 2032 batteries that are supposed to last up to 1 year in the device.

Remotely triggering things is another possible application for technology. I’ve played with both WiFi and Bluetooth controlled relays, and by hooking up an electric match and battery to some fireworks I’ve created a remote fireworks controller. Note that the WiFi one needs to be connected to a WiFi network, and the Bluetooth one is limited to about 30’, so neither is a great solution if you need to be further away. In that case I recommend you consider some standalone wireless remote relays, which use a lower frequency and have a much greater range, even through obstacles.

There are lots of other possible applications for technology that can help if you’re out in the field, making your way in a TEOTWAWKI world. A few more ideas are:

  • Range finder – For some reason I’m lousy at estimating ranges.
  • Handheld weather station – For keeping track of changing weather conditions.
  • Air quality monitor – This would be useful if you’ll be operating near any potential sources of dangerous chemicals.
  • Casio sensor watch – Besides being a great solar-rechargeable watch that’ll last for years, it includes a compass, barometer and thermometer.
  • Portable Lightning Detector – If you live somewhere that gets frequent severe thunderstorms, this could save your life.
  • Electronic lighter – These can be recharged via USB, and some even come with a flashlight.
  • Geiger counter – If you live within a hundred miles or so of a nuclear facility, or you’re concerned about nuclear war.

And finally, the electronic gift for the prepper that has everything when money’s no object – a Boston Dynamics Spot Robot to help carry the load – only $74,500!


I’ve covered a lot of different technology options, so some of you are probably thinking that there’s no way you could afford, carry or use all of these things, and I’m not suggesting that you do so. My goal for this article was to provide some information on various technical options that could increase your effectiveness when you’re mobile in a post-TEOTWAWKI world, and as always you should start with understanding what scenarios you’re concerned about, what your area of operations looks like, what you plan on doing and how you plan on moving around. Once you’ve got a handle on those you can begin to understand how you may be able to apply the appropriate technologies to improve your effectiveness in the areas that are most critical to you. At a minimum, I’d recommend that you start by looking at what you may already have (like a cell phone) and how you could use it in a post-disaster scenario, then expanding from there. I’ve only scratched the surface of some of the technologies you could use, so if you have any other ideas or suggestions please share them in the comments.

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