The Prepper Journal

Hardening Prepper Communications Against EMP

As Preppers, we all continue to observe the world around us and update our threat assessment profile; at least that’s the plan, right? Recent events on the Korean peninsula have many Preppers considering the increased potential for a high-altitude electromagnetic pulse strike (‘HEMP’) against America. The same threat also stems from rhetoric that has already been issued by Iran.

Should a HEMP strike occur, it will most likely take down most if not all of the national electrical grid, in which case we would enter into a worst-case grid-down survival scenario. In this event, having some communications post-event is critical for many reasons.

Preppers who have two working radios after an event will have a significant tactical advantage in executing their survival strategies.  And coordinating groups of Preppers using radio communications will enhance organizing any recovery efforts that may be undertaken at some point after such an event.

How can you offset the effects of EMP

The first step, if you don’t already own a complement of radio gear is to acquire some quality two-way communications equipment. There are lots of companies that make ‘consumer-grade’ equipment (AM-FM-CB walkie-talkies), which do work well on a limited basis. However, in a dire situation that may last for months or possibly even a year or beyond, having high-quality military-grade equipment is a good investment in survival.

An EMP attack could render all electronics inoperable.

There are many companies who compete in the commercial-military radio communications sector, so choosing a company and its products are usually made by experience or second-hand referrals. In the interest of full disclosure, I must first tell my readers that ICOM America is one of my sponsors.

The reason I chose ICOM America is that prior to their becoming one of my sponsors, I used their equipment for more than 20 years at sea in tough unforgiving conditions (heat, cold, seawater, etc.) and never had a single failure with one of their products. As a professional mariner, I cannot (and could not) afford to have any equipment failures at sea. Such a failure could be a death sentence. So, well before ICOM America became my sponsor, I was literally betting my life on their radios.

Faraday Cage made from a stainless steel trash can.

With that said, I highly recommend that readers who are interested in affordable high-quality, robust radio gear visit ICOM’s website, where you can find a local dealer to help you with your individual needs. They handle all types of radio gear, including VHF, HF & HAM radios, which you can buy without any license.

I recommend buying ‘Marine’ radio gear since it is built to withstand the unforgiving marine (ocean-going) environment. For instance, their marine-grade VHF radio transceivers are sealed so well that they are waterproof (submersible) and meet stringent Mil-Spec ratings for many adverse conditions.

Many of their radios have built-in scramblers, which makes overhearing communications between you and your team members virtually impossible (an important feature in some scenarios).

In order to have a communications capacity post-event (HEMP), Preppers need to implement EMP countermeasures for most if not all of their communications devices. This sounds like a daunting task, which is probably why many Preppers have failed to employ any EMP countermeasures on their communications equipment.

No products found.

Generally speaking, the risks that are posed from a high-altitude electromagnetic pulse weapon to your radios are from;

  • a. Direct exposure of the radio and its circuitry to the electromagnetic pulse; and
  • b. Pulse energy enters the radio equipment through its antenna’s coax or other cables connected to the radio.

With regard to the first instance (‘a’); Shielding (Faraday Caging) is the key principle in protecting the radio chassis and its circuitry. This can be accomplished by various means, which are outlined in the document that is associated with this article. With regard to small portable and handheld radios, this can be as simple as putting your radios into a Styrofoam package (ice chest) and then placing that into an all-steel garbage can with a tight fitting lid.

With regard to the second instance (‘b’) there are various types of coax, cables, and filters that can be used that will either stop or attenuate the damaging pulse energy. Due to the size and installation considerations coupled with the fact that you may be using your radio(s) on occasion, fixed-radios, such as base-stations are more difficult to store in Faraday Cages than small hand-held radios. So one option is to protect them ‘in-place’, such that a surprise attack does not catch your radio without some protection. EMP filters on all cables and coax will also help protect against lightning damage to fixed radios.

First, with the recent advancements in EMP filter technologies, many in-line (coax and control cable) filters have become mainstream and are easily within reach (cost and availability) of all Preppers. I have included a link to one of many vendors (not affiliated to me) herein below.

Second, there is an abundance of information on ‘how-to’ harden your radio systems, which can be implemented with relative ease now that we can access filters and cables that work. There are many excellent papers by various HAM radio groups and others on ‘how-to’ harden your gear, and I have provided one such document as a download herein below, as well the link to an online vendor for EMP filters.

I hope that this brief article helps you to get started, or if you’re already radio-prepped, get your EMP countermeasures dialed-in.


Capt. Bill

EMP Filters (Online)

Catalog of EMP filters, connectors and cables (PDF)

Paper on hardening your radio system by Dennis Bodson, W4PWF Acting Assistant Manager, Technology and Standards National Communications System – Washington, DC 20305-2010

Capt. William E. Simpson II is a U.S. Merchant Marine Officer with decades of boating and expedition sailing experience, who has successfully survived long-term off the grid at remote uninhabited desert islands with his family using sailboats that he equipped for that purpose. Capt. Bill holds a U.S.C.G. 500-ton captain’s license for commercial inspected passenger vessels, including, power, sail and assistance towing vessels. He is also the author of many articles on sailing and the book ‘The Nautical Prepper’ (Ulysses Press) You can read more from the Nautical Prepper on Capt. Bill’s personal site at

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