You might have already seen this headline today, but I thought it worth posting here in case anyone missed it.
http://watchdog.org/138940/solar-flare-emp/ (http://watchdog.org/138940/solar-flare-emp/)
The article mentions that an EMP or severe solar flare "can disturb the space weather around the Earth and affect communications signals traveling through the upper atmosphere."
Assuming one has taken precautions and has a protected mode of generating power and transmitting shortwave, how long would it take after such an event for HF propagation to resume to a workable state?
I wonder just what is a reliable means of protecting electronics such as ours from an EMP?
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Quote from: NWARadio on April 21, 2014, 04:06:50 PM
I wonder just what is a reliable means of protecting electronics such as ours from an EMP?
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Dirt simple solution............. Faraday cage. RF current passing being conducted in a conductor flows on the surface of the conductor, AKA; skin effect. If the electronic device is enclosed inside of a conductor (metal box), the electromagnetic energy will simply conduct on the surface of the box and never reach the device. By all rights the Faraday cage should be grounded but chances are just tossing a radio into a .50 cal. ammo can will protect it just fine. For a little more protection place the ammo can inside a metal file cabinet for an extra layer of protection. Of course this does nothing for the rig sitting in your shack with an antenna connected to it, if it's exposed to the massive dose of RF it's toast.
That's why I built my station-in-a-box inside an Army surplus medical instrument case. Everything in it will be protected.
Years ago I was taking a training course at Los Alamos National Labs. The course was on lightning and bonding/grounding. I brought this topic up to the phd EE that was teaching the class. He told me to place a shorting connector on the antenna jack and wrap the radio in a ESDS plastic bag, then store the radio in a metal enclosure, like an ammo can. This instructor wrote the book on lightning and bonding/grounding and he was a ham. I am pretty sure he knew what he was talking about.
I am too busy playing with different radios to sideline one and take it out of action. I have some duplicate radios and maybe that is what I should do with one of these spair radios. Right now I can spair one Tentec Corsair and a Tentec Argosy(after I make a few needed repairs). Since mo0st of the repeaters would be knocked off the air, not real sure if one HT would do any good. Maybe a set of HT's would be the best option. Heck, three or four FRS HT or some CB's would work great since the airwaves would be silent. 73'S KA5SIW
ARRL members can download a 4 part series of articles published in QST during 1986 called "Electromagnetic Pulse and the Radio Amateur". Part two is available to anyone but I think you have to be logged in to download 1, 3 and 4. Part 4 gets to the meat of things with specific recommendations and diagrams on protecting a station.
The articles document tests run by the Federal government in testing amateur radio equipment because of the importance of MARS back then. Direct testing with EMP test devices showed radios with no external wiring connections - no antenna, mic or key cables, tuner connections, etc did very well with no protection. Significant additional protection could be gained with transient voltage suppression devices like Polyphasor.
One key finding in the series is that most of the energy in an EMP is below 10 MHz, with 99% below 100 MHz. This gives you a feel for how long a wire needs to be to serve as an effective antenna to introduce EMP into a piece of equipment.
Wally
I'll download these today when I get off work. Sounds very interesting.
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Thanks Wally for pointing out those old ARRL articles. I've reviewed them briefly last night and here are my take-aways:
- A high altitude EMP will damage the nation's power grid and could damage unprotected electronics across most of the continental USA. It might not destroy all electronics, but their function could be diminished.
- Some lightning suppression devices can help isolate your station from your antenna and from commercial AC power, if the suppression devices are properly installed and other common grounding techniques are employed.
- For extra protection, spare electronic equipment should be placed in a metal box/faraday cage with any antenna or external mic unplugged from radio. Electronic equipment needed to generate electricity and properly recharge batteries would also need to be stored in a faraday cage for maximum protection.
- EMP hits the HF frequencies hard and will disrupt HF propagation for hours, but should be useable again within a day. Line of sight and ground wave propagation should be unaffected.
- Repeaters would probably be toast; although line of sight use of handheld radios could be useful within your community.
- CW on HF would be the most reliable means of long range communication immediately after an EMP event.
QuoteCW on HF would be the most reliable means of long range communication immediately after an EMP event.
Isn't that a surprise ;)
I've been promoting Morse code heavily here for good reasons.. It's not just ramblings.. CW will cut through when other modes fail. Radios are smaller, cheaper, simpler and draw less current.
- "Yeah but it's a pain in the ass to learn..."
- "Just get off yours and learn it!" ;D
Gil.
Quote from: gil on April 24, 2014, 11:28:06 AM
QuoteCW on HF would be the most reliable means of long range communication immediately after an EMP event.
Isn't that a surprise ;)
I've been promoting Morse code heavily here for good reasons.. It's not just ramblings.. CW will cut through when other modes fail. Radios are smaller, cheaper, simpler and draw less current.
- "Yeah but it's a pain in the ass to learn..."
- "Just get off yours and learn it!" ;D
Gil.
What he said 8)