About shielded pouches.

Shielded pouches come in a wide variety of shapes, sizes, and prices. Some gourmet potato chips, for example, come in metallized bags that preserve freshness. If these bags are sealed tightly and carefully, some of them will, quite unintentionally, provide a modest amount of electromagnetic shielding.

For under $5, some paint stores will sell you a clean, shiny, unused, 1 gallon paint can. Sometimes a paint can will also disable wireless devices, replacing a more expensive shielded pouch. Copyright 2007 by the Herndon Company. All rights reserved.

Ground coffee comes in heavy metallized bags that, in a pinch, might also work as shielded pouches.

How can you tell if a home-made shielded pouch actually works? A quick way is to place a call to your cell phone, verify that it rings, then hang up. Now put the cell phone in your home-made shielded pouch. Place the call again. If your cell phone does not ring, your home-made shielded pouch has temporarily disabled THAT ONE PHONE. It may or may not disable other wireless devices. You would have to try it with every single one.

Several manufacturers offer shielded pouches, ranging in price from under $20 to over $1,000.

With such a wide variety of shielded pouches available, an intelligent consumer might ask: "Why spend a lot of money for a shielded pouch, when I might make do with a paint can or a potato chip bag?

The answer lies in terms of the shielded pouch's ruggedness, its reliability, its useful lifetime, its ease of use ( which is critical in security applications,) and a technical term known as SHIELDING EFFECTIVENESS.

The SHIELDING EFFECTIVENESS of a shielded pouch is a measure of its ability to keep radio signals from getting in or out. Shielding effectiveness is measured in decibels (dB.) A shielded pouch having a shielding effectiveness of 20 dB will reduce the field strength of an incoming or outgoing radio signal by a factor of 10:1. One with 40 dB will reduce it by 100:1. One with 60 dB will reduce it by 1,000:1 and so on.

A well-designed, well-built shielded pouch may provide a shielding effectiveness of 80 dB or more. A potato chip bag may only provide 20 dB. A paint can might provide up to 80 dB, but it is difficult to open and close, it is easily damaged when dropped, and its lid can wear out, be deformed, or rust. Copyright 2007 by the Herndon Company. All rights reserved.

Shielding effectiveness also varies with frequency. A shielded pouch that provides 80 dB at one frequency may only provide 20 dB at another. This is why a critical part of the shielded pouch manufacturing process is TESTING. Shielding effectiveness testing requires specialzed equipment and trained people, all of which adds to the cost of the shielded pouch.

The Herndon Company's "Cartersville" and "Ayr Hill" shielded pouches were designed by electronics engineers under a U.S. Government contract, specifically for the purpose of temporarily disabling cellular telephones, personal digital assistants (PDA's), and other wireless devices.

Our shielded pouches are designed to provide a robust level of shielding effectiveness over many years of trouble-free service.

Our shielded pouches are assembled using proprietary, state-of-the-art techniques that are unique in the industry.

Every one of our shielded pouches is made and tested in Virginia, exclusively by United States citizens with security clearances.

Our shielded pouches are neither the cheapest nor the most expensive shielded pouches available. We have good reasons to believe that they are currently the best ones in the world. Copyright 2007 by the Herndon Company. All rights reserved.

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