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 Post subject: EMP radio
PostPosted: 14 Feb 2018, 12:32 
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This is just a fun post,

I was talking to someone the other day and a discussion came up about EMP from nuclear weapons.
So this thread is a general talk about circuits for a hand held radio that could be built/used to listen for radio transmissions after an EMP strike.
All a bit nuts I know but the conversation went from shielding to tubes to low power tubes etc. :confused: :nuke:
Any thoughts.

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M. Gregg

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 Post subject: Re: EMP radio
PostPosted: 14 Feb 2018, 13:47 
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Interesting ideas,

http://www.futurescience.com/emp/emp-protection.html

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M. Gregg

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 Post subject: Re: EMP radio
PostPosted: 14 Feb 2018, 21:52 
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Hi, Back to the crystal radio. A paper tube wound with magnet wire, crystal phones and a 1N34. Keep all the parts in the tube and stuff it in a metal can. You can get fancy with a second coil coupling and air core tuning capacitor. Some designs are quite excellent. Of course if you use tubes and it is powered off at the time it will be fine, peanut tubes and a solar power supply (or wind) and you will be good to go. Use mechanical componets where posible to avoid possible EMP damage. I believe if the solar cells are off line they should be fine. A car battery for power storage (also off line).

Good listening
Bruce

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 Post subject: Re: EMP radio
PostPosted: 16 Feb 2018, 17:17 
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Car battery s are not good for this. They will die! They are for high current for short periods of time not long low current aps. What you need is a AG M battery. AKA deep cycle. I Have soloa r for back up and I use for lift batterys. I also have some agm. Please note these are rated in amp hours not cca. Also you can only use 50% of your total amp hours of your battery bank of you will kill your batterys. So if you need 250 amp hours of use you will need 500 amp hours of battery. I have 2000 watt hours of back up for my home and 1KW in mono crystal solor pannels. Mono are better than Polly pannels. All of my radio gear is di y tube crystal controle d transmitters and a cathode modulated TNT transmitter and all tube recivers.

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 Post subject: Re: EMP radio
PostPosted: 16 Feb 2018, 20:53 
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True, I was thinking of deep cycle or gel cells.

Good listening
Bruce

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 Post subject: Re: EMP radio
PostPosted: 18 Feb 2018, 04:57 
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Some interesting replies,

I thought this EMP idea was interesting because of the number of times you try to shield a power Tx from output transformers or to stop circuit interference.
Its obvious from the Article now that the frequency of the pulse has a marked effect on the ability to shield from it.
I never thought about the way a microwave is shielded.

Its quite interesting in the article,
Quote:
Items like surge suppressors and ferrite suppression cores are only going to be effective against relatively small pulses that come in through the power line. A large EMP will totally and completely fry your large screen television by directly inducing currents in the equipment itself that are far too large for it to handle. The same is true for much of the other electronics in your home. There is no reason to assume, though, that any EMP attack will be maximally effective -- or that you will never be right at the edge of the affected area. Also, even if an EMP attack never happens, an endless barrage of small voltage spikes is eating away at your electronics equipment every day unless you are doing something to protect against it.

I was also wondering if amo bead suppression could help on rectifiers, or if perhaps amo bead (zero crossing current) on one side of a diode and ferrite bead on the other leg. I have never tried it.
http://toshiba.semicon-storage.com/us/p ... beads.html
and
http://toshiba.semicon-storage.com/cont ... s_Work.pdf

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M. Gregg

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 Post subject: Re: EMP radio
PostPosted: 18 Feb 2018, 07:15 
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OK a moment of stupidity,

This is just fun please don't put your cell phone in a micro-wave :D
I watched a youtube video about microwaves:
https://www.youtube.com/watch?v=ot4_jVFXxUU

Which also led me to look at this:
https://www.google.co.uk/search?q=Micro ... 00&bih=750
Question, does anyone know is the mica wave guide cover sprayed with conductive paint or is it just a Mica insulator board?
Reason for question: Mica capacitors sound quite good, could you use this as a turret circuit board?
Daft question but I have never seen a Mica cover sheet. If its conductive then obviously its no good as a circuit board.

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M. Gregg

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 Post subject: Re: EMP radio
PostPosted: 18 Feb 2018, 09:17 
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Interestingly,

The EMP shield or Faraday cage seemed to be dependant on grounding or not.
This brings up the question about drain wires and if the shielding is EMP or signal shielding.
Could a drain wire benefit from a ferrite bead? Never though about really.
Scopes tended to use Mu-metal around the CRT.
LMAO OK I've just seen a Faraday cage for car keys (theft/solar pulse).

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M. Gregg

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 Post subject: Re: EMP radio
PostPosted: 18 Feb 2018, 13:28 
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About the mics cover in an microwave oven they are well we're solid mica. That being said it has been over 25 years since I serviced one. I still have some new old stock left.

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 Post subject: Re: EMP radio
PostPosted: 19 Feb 2018, 13:50 
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Alpha Wolf wrote:
About the mics cover in an microwave oven they are well we're solid mica. That being said it has been over 25 years since I serviced one. I still have some new old stock left.


I know that when working with Mica cutting /drilling you must wear a mask. (dust is a problem)
But its another idea as long as there is no conductive layer/deposit on the board.
https://en.wikipedia.org/wiki/Mica

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M. Gregg

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