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Old 17-03-2014, 15:36   #1
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Faraday cage for hand held GPS

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Originally Posted by DoubleWhisky View Post
And... Do not know, what is Boatie's custom, but I always have on board old fashioned, hand held GPS (no maps, simplest functions, low consumption) and a boatload of spare betteries...
By the way, I want to order metal box, isolated inside, as a Faraday box, to store hand held inside (in case of lightning).
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Use your oven for the hand held
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It is what I'm doing now, but my Dearest and Beloved Supreme Authority is somewhat opposing to this custom
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Originally Posted by Seaworthy Lass View Post
The alternative is to get an aluminium boat. The whole interior acts as a Faraday cage .
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Originally Posted by DoubleWhisky View Post
Alu boats have a lot of advantages...
Biggest disanvantage for me is simple... PRICE ! ! !
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In general, this won't help you with the magnetic part of the pulse.
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My oven is a bit heavy for that, and according to the instructions, does not have that feature built in.

Coops.
I have unwillingly created this drift on Boatmans delivery thread...

So, to put the topic in the proper place...

Do You think it is possible to create a box, being Faraday cage, for safely storing the handheld GPS and protecting it effectively against lightning?
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Old 17-03-2014, 15:43   #2
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Re: Faraday cage for hand held GPS

Hi, there, DW,

Sure, use the pressure cooker. All metal box. Works okay, I guess. Haven't been struck by lightening to test it. Do use a dissipator at the masthead.

A steel toolbox would work, too.

Ann
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Old 17-03-2014, 15:45   #3
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Re: Faraday cage for hand held GPS

nothin steve austin can't handle
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Old 17-03-2014, 15:46   #4
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Re: Faraday cage for hand held GPS

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Originally Posted by Ann T. Cate View Post
Hi, there, DW,

Sure, use the pressure cooker. All metal box. Works okay, I guess. Haven't been struck by lightening to test it. Do use a dissipator at the masthead.

A steel toolbox would work, too.

Ann
Hi, Ann

What disturb me now is this magnetic impulse mentioned by LakeSuperior.
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Old 17-03-2014, 15:48   #5
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Re: Faraday cage for hand held GPS

Absolutely, or do like eveyone else and put the GPS in the Microwave or oven with a sign on the door. DO NOT USE
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Old 17-03-2014, 15:55   #6
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Re: Faraday cage for hand held GPS

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Absolutely, or do like eveyone else and put the GPS in the Microwave or oven with a sign on the door. DO NOT USE
My Dearest gets angry, when I'm trying to use the appliances and utensils "unproper way"
As I prefer to see Her smiling all the time, I'm seriously looking at other solution
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Old 17-03-2014, 16:03   #7
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Re: Faraday cage for hand held GPS

Get a steel ammo box from a military surplus store - they're waterproof and you don't have to worry about accidentally cooking your GPS.
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Old 17-03-2014, 16:15   #8
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Re: Faraday cage for hand held GPS

How would a small (hotel room size) safe work for this? I have one my mother used to use, and was thinking of installing it on the boat anyway. I never put anything in the oven that can't handle being cooked.
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Old 17-03-2014, 16:18   #9
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Re: Faraday cage for hand held GPS

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How would a small (hotel room size) safe work for this? I have one my mother used to use, and was thinking of installing it on the boat anyway. I never put anything in the oven that can't handle being cooked.
Great idea, I think - thank You
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Old 17-03-2014, 16:35   #10
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Re: Faraday cage for hand held GPS

Hmm - maybe it's just me, but I seem to see a lot of reassurance happening here, but not much information.

Are people dismissing the magnetic pulse issue because they know it's not a problem, or because they don't know it's a problem?
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Old 17-03-2014, 16:47   #11
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Re: Faraday cage for hand held GPS

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Hmm - maybe it's just me, but I seem to see a lot of reassurance happening here, but not much information.

Are people dismissing the magnetic pulse issue because they know it's not a problem, or because they don't know it's a problem?

I'm asking, not dismissing anything. I'd like to know what would work, if anything. I heard a guy the other day on an NPR radio show, who demonstrated (at a TED conference, maybe?) some uses for small drones his company can make. One thing he mentioned was the possibility of a drone delivering a small EMP to, in his example, other drones with paparazzi cameras which were following a famous person. Yikes. I thought, great, the other drone is disabled, but what about someone's car close by? Or boat -- those pesky famous people seem to like the water.
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Old 17-03-2014, 17:31   #12
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Re: Faraday cage for hand held GPS

Hi there. Just wanted to shed some light on this topic, as there seems to be a bit of misinformation on what a faraday cage does, and how they basically work.

First off, lightning strikes and EMP's are not the same thing. EMP's can generate lightning, but lightning does not. First of all, they are made up of completely different fields. Lightning is electrostatic, and EMPs are...well...you know what they are. Magnetic fields.

Faraday cages do two things. They create a medium for charge to pass through that has a much lower resistance than an air gap so that charge can accumulate within the conductive material of a cage, and they use some sort of connected symmetry in order to associate positive and negative charge around the cage so that they cancel each other out, thereby creating a zero field effect in the area within the cage (provided that the cage is not tied to ground). The only useful way to use a faraday cage in your situation would be if you do not have a lightning diffusor or some other system to manage a strike, and want to isolate critical systems from the rest of the electronics of the vessel, or protect against lightning tendrils.

Protecting against a lightning strike directly to the cage is not really feasible, or really what is meant by a faraday cage. If there is enough potential (voltage) to spark an air gap that size...all you can do is try and route the discharge to a ground plane (the sea). Any conductive material within grasp will not hold up to 30,000 amps very well. If the lightning bolt can create enough ESD to turn O2 into plasma, then its going to melt some wires that have a way lower resistance than air. What it does is protect from electrostatic fields generated in the vicinity of the strike, which will have a very low current. A mast diffuser is a must. However for the cage for sensitive electronics would involve something like several layers of electrically commonly wired mesh (like a fine chicken wire) organized in a cube shape, with some insulation on the inside to isolate your valuables. Better than this would be perforated sheet metal. Just remember that all 6 sides should be equal in material, and all have the same resistance, or conductance really between them, and have the same amount of space on all sides to the products you are wanting to protect. (same air gaps on all sides). I am saying 6 sides because especially when under way, you won't predict the direction and thereby strength of magnitude of incoming electrical fields.

I would avoid using things like appliances (microwaves, safes) because they are covered in a lot of material inside and out that really don't give two fingers about conductances but will easily catch fire, and if ignited by electrical shorts due to wires melting and arcing at WAY above tolerance currents, then a gps quesadilla is just as bad as a fried one.

This assumes that you are going to put your GPS in the cage (completely disconnected) before lighting strikes. If your goal is to have it run and live inside the shield, then something more complex is required.

There are many retail systems to deal with a mast strike, and they will be sufficient to guard your electronics. And unless you are worried about a storm about the size of the eye of jupiter, being above nuclear test sites, massive unprecedented solar flares, global magnetic field reversal or the end of times...you really don't need a faraday cage on a boat for your GPS. Even if you did, you should be more worried about replacing GPS satellites rather than protecting the garmin unit.
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Old 17-03-2014, 17:54   #13
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Re: Faraday cage for hand held GPS

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Originally Posted by ionic View Post
Hi there. Just wanted to shed some light on this topic, as there seems to be a bit of misinformation on what a faraday cage does, and how they basically work.

First off, lightning strikes and EMP's are not the same thing. EMP's can generate lightning, but lightning does not. First of all, they are made up of completely different fields. Lightning is electrostatic, and EMPs are...well...you know what they are. Magnetic fields.
You speak with authority...below is an excerpt from the first hit on a Google search. Seems to contradict your statement here.

More to the facts, it is basic physics that accelerating charged particles radiate away energy in the form of electromagnetic waves.

From:
Lightning - Wikipedia, the free encyclopedia

"The rapidly changing currents also create electromagnetic pulses (EMPs) that radiate outward from the ionic channel. This is a characteristic of all electrical sparks. The radiated pulses rapidly weaken as their distance from the origin increases. However if they pass over conductive elements; i.e., electrical wires, communication lines or metallic pipes, they may induce a current which travels outward to its termination."
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Old 17-03-2014, 17:56   #14
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Re: Faraday cage for hand held GPS

Greetings and welcome aboard the CF, Ionic.

I'm not certain I find your opinion entirely convincing.
Notwithstanding, thanks for contributing a technical reply.
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Old 17-03-2014, 18:00   #15
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Re: Faraday cage for hand held GPS

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There are many retail systems to deal with a mast strike, and they will be sufficient to guard your electronics. And unless you are worried about a storm about the size of the eye of jupiter, being above nuclear test sites, massive unprecedented solar flares, global magnetic field reversal or the end of times...you really don't need a faraday cage on a boat for your GPS. Even if you did, you should be more worried about replacing GPS satellites rather than protecting the garmin unit.
This is statement is complete misinformation. Lightning strikes are not one size fits all. A seriously big hit will overwhelm just about every countermeasure known to man. The consequences of a strike are unpredictable and potentially catastrophic. Nothing is assured.

The electronics are usually the first to go in any strike as they are normally unprotected from the accompanying EMP.
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