NEW FACTS ABOUT EMP

BY R. KENNETH MITCHELL, KA6FRD

The National Communications System (NCS), a governmental entity made up from 22 different Federal agencies, wants ham radio operators and their gear to survive an EMP (Electro-Magnetic Pulse) generated "nuclear event."

NCS engineers have simulated the EMP phenomenon in the laboratory and have subjected various pieces of current amateur radio gear to its effect.

The people at NCS came to some rather surprising conclusions.

In their report they say, "It was concluded that modern solid-state amateur radio equipment was more survivable in an EMP transient environment than had been previously anticipated."

What makes those sophisticated and delicate transistors and ICs so survivable?

The secret is in having two EMP surge protection devices. One is needed on the end where the power comes into the radio and the other on the antenna end where the RF signal goes out.

The NCS tested various commercially available suppression devices designed for both lightning and EMP and, in a move surprising for any governmental agency, issued a report telling which ones worked and which ones didn't.

Their findings and recommendations are outline in a 105-page publication entitled "Electromagnetic Pulse/Transient Threat Testing of Protection Devices for Amateur/Military Affiliate Radio System Equipment"--otherwise known as NCS Technical Information Bulletin 85-10.

When considering EMP protection for transient voltage spikes coming in through commercial power lines, the folks at NCS
recommend the TII model 428 plug-in power line protector, an item which costs only $45. But for those a little strapped for cash (and what survivalist isn't), the report shows how you can make one yourself for an estimated cost of only $11.

For EMP protection on the antenna side of a rig, NCS recommends the Fisher series of spikeguard suppressors. They come in a variety of different clamping voltages, depending on the characteristics of a specific station.

The bulletin provides a mathematical formula to determine which fisher model is correct for your radio.

The Fisher devices cost $55, thus giving hams total effective EMP protection for their radios with off-the-shelf items for only $100.

If your radio has a power output of 100 watts or less, a second coax protector was recommended, the PolyPhaser products. They proved to be just as effective as the fisher products but cost somewhat more--$82.95 each. Because of their lower clamping voltages, they are recommended only for lower wattage transmitters.

But again, for those handy with electronics, NCS shows you how to make a simple home-made protection device for your antenna system for only $9.

It was interesting to note that two relatively inexpensive devices simply did not work. The Archer (Radio Shack brand) AC
line protector was NOT recommended. Nor was the Alpha Delta brand "Transi Trap" coax protector, commonly advertised in ham radio magazines.

Other interesting findings made by NCS engineers were that portable generators, such as Honda types, were not likely to be adversely effected by EMP at all. Neither were hand-held walkie-talkie type portable radios, particularly those with short stubby "rubber duck" antennas.

The importance of a proper grounding system for amateur radio stations was discussed in the report with specific recommendations for maximum effectiveness.

Here is response from Brian - AB1JU:
Interesting...
But, are you aware that the publication that is mentioned is from 1985?

I found it and attached it if you'd like to check it out.

I'm sure most of it still applies, but technology has gotten much better since then. So, I would not be sure that their recommendations for surge / emp protection would still be accurate today.