Patrick,
1980 I had just finished installing shielding and rewiring a 66,000 square feet
research building in order to minimize the EMI/RFI problems that existed in the
building when it was just finished. Not that is has much to do with EMP effects
on digital watches.
I do know that the radio spectrum from the EMP is much wider (contains higher
frequencies) than the spectrum from a lightning strike. It is hard for me to
understand that a digital watch can be destroyed without the wearer being
severely medically affected such as external and/or internal burn damages.
Well, I wasn't there to see it myself so ...
Hans - N2JFS
-----Original Message-----
From: Patrick Greenlee <patrick_g@windstream.net>
To: towertalk <towertalk@contesting.com>
Sent: Sun, Apr 19, 2015 10:11 pm
Subject: Re: [TowerTalk] Fwd: Near Field Lightning Damage
Well Hans, I was there when the vessel made port (about 1980.) Where
were you?
I took a sabbatical from my usual employ and worked for a
short while in field
service engineering for two San Diego based firms,
Marine Electric and Honor
Marine. I held a commercial radiotelephone
lisc with ship's RADAR
endorsement.
Being suspicious and skeptical of an anecdotal retelling of a
once upon
a time tale is a trait we share but I personally would avoid calling
a
witness to the fried equipment a liar by any means, however indirect.
Oh,
and these digital watches were not metal encapsulated on the side
where the
wearer was intended to view the readout.
Admittedly this was a one off
occurrence in the collective experience of
the waterfront electronics types I
talked with about the event. Much
more common was to lose goniometers in RDF
equipment due to antenna
position (highest point aboard but usually not much
else.
Patrick NJ5G
On 4/19/2015 2:44 PM, Hans Hammarquist via TowerTalk
wrote:
> This sounds very anecdotal. Yes, a near strike lightning may take out
CB radios etc but that it took out digital watches make me suspicious. The are
usually metal encapsulated and very immune to external field. I believe a EMP
strong enough to take out a watch also will take out the person carrying that
watch.
>
>
> Depending on the grid size, a Faraday cage is useful for the EM
from a lightning as the "M" will introduce back EMF in the cage which will
neutralize the "M".
>
>
> I hope the "falme" will not be too long,
>
>
>
Hans - N2JFS
>
>
>
> -----Original Message-----
> From: Patrick Greenlee
<patrick_g@windstream.net>
> To: towertalk <towertalk@contesting.com>
> Sent:
Sat, Apr 18, 2015 10:18 pm
> Subject: Re: [TowerTalk] Near Field Lightning
Damage
>
>
> Back in the 80's a tuna boat pulled into San Diego with every
device on
> board
> containing a semi-conductor inoperative. CB radio, Marine
VHF,
> SSB, SONAR,
> RADAR, VHS tape player, SatNav LORAN, and on and on...
All
> the crew members
> wore digital watches which were all totally
dead.
>
> One near miss by a large
> lightning stroke took out everything
with solid
> state semiconductor junctions.
> The good news was they didn't
have a
> spotter chopper aloft at the time
> dependent on the aircraft beacon
band
> transmitter on board to find the boat
> (helipad is the roof of the
pilot
> house.) We theorized it was the EMP that
> ate everything as there
was no
> evidence that the bolt hit the boat.
>
> Later
> when asked what
could be done to provide an immune backup comm
> radio we told
> them a mu
metal box. A Faraday cage wouldn't stop the
> magnetic pulse.
>
> Just
> a
thought in case there are any serious preppers in our midst.
>
> Patrick
>
NJ5G
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