1. posterid:244139
  2. Farraday cage time for equipment?

Re: Farraday cage time for equipment?

Paul Butzi (W7PFB)
 

What about the gap thru which the magnetron injects microwave radiation into the cavity? 

Either the magnetron is outside the shielded cage and there’s a window it injects thru, or the magnetron is inside the cage and there’s a power feed thru the wall of the cage. Either one defeats the cage in the event of an EMP. 

-p

On Feb 25, 2022, at 6:05 PM, Rowland <rowland.brasch@...> wrote:


Read an article several years ago about using a non working microwave as it is completely shielded so microwaves cannot leak out during use. So the RF cage will shield equipment inside from bad things on the outside.


Thanks,

Rowland



On Fri, Feb 25, 2022 at 1:20 PM Lou Giliberto (KD7HCW) via groups.io <louis.giliberto=protonmail.com@groups.io> wrote:
Here's the nerd answer:  https://physics.stackexchange.com/questions/230728/would-a-faraday-cage-protect-something-from-an-emp

Having used them for telcoms stuff, you really do need to make sure they are "completely sealed".  Any kind of wire running out from them (e.g., power) will cause signal and such to leak in.  

They also make "faraday bags" which are what they sound like - a bag you put an object into and it provides some measure of protection.  We used that and a metal garbage can with a ground strap when we wanted to test loss of signal stuff for telecoms.  Cell phone signals are designed to be very aggressive so that our phones work.  If the EMP burst is purposeful, it, too, will be aggressive. There are also "faraday tents" but they often leak like a sieve.

Step one is the EMP burst on the equipment.  Step two will be the EMP burst effects on your power source (e.g., the grid, generators, batteries) and anything along the antenna path that is susceptible (e.g., rotor, loop amplifier, etc.).

+1 for tube amps which are more resistant to the effects.  Sometimes the old ways are the best ways. I should build a spark gap transmitter ;-)


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------- Original Message -------
On Friday, February 25th, 2022 at 7:12 AM, Robin WA7CPA <wa7cpa@...> wrote:
Someone on 100 Watts and a Wire suggested it may be Farraday cage time. Only asking for suggestions on creating them.  Not trying to start a geopolitical discussion. Seems easier for the handhelds.  My biggest concern is HF equipment. Pointless to try? Metal roof overhead. Basement windows could be covered with what effective material? What about the concrete walls? Anyone delved into this theoretically? 

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