There was a story on ABC Television "Nightly News" a few
months ago about cars being hit by lightning. When they do get
hit, they don't do so well. The damage ranges from ruining all
the electronics to catching fire and the vaporization of tires
and parts of the car body.
Whether or not the car is negative or positive ground
probably makes no difference when you subtract 12 volts from
100-million volts. I read somewhere where the energy level in
your average lightning strike is one times ten to the
twenty-third jules. Yup, that's 23 zeroes.
In all seriousness, a metal car body probably does
provide some degree of protection for you in that the charge may
travel around those in the car through the body rather than
through the people but when you're dealing with these kinds of
voltage and energy levels, all bets are off.
O yes, be sure to set your clock to some date you think
you can handle as you listen to Hewy Lewis sing "The power of love."
Martin
Frank Ventura writes:
> Are you kidding me? Lets think a minute about what lightning is. It is
> an =
> electrical arc, in this case between a cloud and the ground. The arc is
> neg=
> atively charged particles looking for a positive ground, as opposites
> attra=
> ct. Some lightning strikes contain as much as one billion volts (remember
> t=
> he first Back to the Future movie?). If that awesome charge is strong
> enoug=
> h to arc several miles through open air can you imagine how easily it can
> a=
> rc through a rubber or glass insulator. It is amazing how many people
> belie=
> ve that the rubber tires of a car keep it from being hit by lightning.
> Ther=
> e are two basic reasons why cars don't get hit by lightning with the
> latter=
> being more important, they are:
> a. Cars are relatively low to the ground and are rarely in a position to
> be=
> the path of least resistance.
> b. Almost all cars have negative ground electrical systems. Remember from
> a=
> bove that lightning is a negatively charge partical arc looking for a
> *posi=
> tive* ground to strike. A negatively charged arc is not attracted to a
> nega=
> tive ground. Rubber tires have nothing to do with it. With all that
> voltage=
> if lightning did hit the car body it would arc the gap from the body to
> gr=
> ound below and probably turn the tires into a molten blob of fake rubber
> in=
> the process. It is the negative ground electrical system that makes the
> ch=
> arges repell not attract. Now with that said there are a few (mostly
> Britis=
> h) cars from the period following WWII that actually have positive ground
> e=
> lectrical systems. Electrically speaking they could attract a negatively
> ch=
> arged arc but I doubt it has happened much due to the reason given in a
> abo=
> ve.
> So in short if you merely disconnect the coax from the connector on your
> ho=
> use and leave it a few inches or even a few feet away from your house you
> c=
> an seal it in glass, wrap it in rubber or shove it in a ham sandwhich for
> t=
> hat matter and lightning can still arc from the cable to your humble
> abode.=
> =20
> Frank
> PS see:
> http://www.google.com/imgres?imgurl=3Dhttp://images.nationalgeographic.com/=
> wpf/media-live/photos/000/002/cache/lightning-over-water_270_600x450.jpg&im=
> grefurl=3Dhttp://environment.nationalgeographic.com/environment/natural-dis=
> asters/lightning-profile/&h=3D450&w=3D600&tbnid=3DzOwdXoP47bq-8M:&zoom=3D1&=
> tbnh=3D160&tbnw=3D213&usg=3D__zkPY7nzoAY6ktc1km2namr1l0No=3D&docid=3D21jTPm=
> qZw7qgRM
>
>
> -----Original Message-----
> From: For blind ham radio operators
> [mailto:[log in to unmask]] =
> On Behalf Of Tom Behler
> Sent: Thursday, June 25, 2015 8:52 PM
> To: [log in to unmask]
> Subject: Re: Grounding Question
>
> Jim:
>
> Here's an idea:
>
> To insulate the coax connector, would it be sufficient to put one of
> those =
> rubber boots around the connector, such as those that you get with new
> runs=
> of coax?
>
> I would think that should be a pretty good insulator.
>
> Tom Behler: KB8TYJ
>
>
> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Jim Shaffer
> Sent: Thursday, June 25, 2015 6:55 PM
> To: [log in to unmask]
> Subject: Re: Grounding Question
>
> Tom I never meant to imply that the virtual ground you have would protect
> y=
> ou from lightning. Unplugging the antenna is the best way to go as far
> as =
> I know. In fact, it's almost certainly true that if the antenna, or part
> o=
> f it, is grounded, that would actually increase your chances of a
> lightning=
> strike. You should disconnect the antenna, and perhaps put the end of
> the=
> coax in a glass jar, or some sort of insulator. That's of course no
> guara=
> ntee, but it might keep a lightning strike on the antenna from starting a
> f=
> ire in your trailor.
> --
> Jim, ke5al
> -----Original Message-----
> From: Tom Behler
> Sent: Thursday, June 25, 2015 11:32 AM
> To: [log in to unmask]
> Subject: Re: Grounding Question
>
> Well, Jim, this is what I'm confused about, and I sure wish I knew what
> wou=
> ld be best.
>
> Of course, I guess putting in a ground rod would not hurt anything, but I
> d=
> on't think I'm going to be able to do that at least for the next few days.
>
> For the past several years, I have used the system I described, with no
> pro=
> blems.
>
> But, of course, that doesn't guarantee that I won't have any problems in
> t=
> he future should the lightning god strike.
>
> It's just a difficult call, in my opinion.
>
> Tom Behler: KB8TYJ
>
>
> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Jim Shaffer
> Sent: Thursday, June 25, 2015 12:01 PM
> To: [log in to unmask]
> Subject: Re: Grounding Question
>
> Tom, from what I've read, what seems important is to be grounded to
> what's =
> around you. It sounds like what you have now is a virtual ground, which
> is=
> supposedly just fine. I'll bet, if you do put down an 8 foot ground
> rod, =
> you'll see no difference.
> --
> Jim, ke5al
> -----Original Message-----
> From: Tom Behler
> Sent: Thursday, June 25, 2015 9:01 AM
> To: [log in to unmask]
> Subject: Grounding Question
>
> Hello, all.
>
>
>
> I know I'll get varying opinions on this, but I have a question about
> stati=
> on grounding out at the RV camp site.
>
>
>
> As many of you know, my main rig out there is my TS480, and I will be
> using=
> my trusty Alpha Delta DXCC multi-band dipole. When all is said and
> done, =
> I'm hoping the antenna will be up about 30 feet in the trees.
>
>
>
> Just as I did in previous years, I will have a ground connection running
> fr=
> om the ground screw on the TS480 to a terminal ground connection on the
> bac=
> k bumper of the RV. I use 10-gauge wire for this connection.
>
>
>
>
>
> Of course, I am very careful about disconnecting my antenna at any sign
> of =
> thunderstorms.
>
>
>
> Is this adequate, or should I be pursuing something additional?
>
>
>
> I wouldn't think a dipole would have to be grounded with a ground rod
> such =
> as is the case with a vertical, or a beam antenna on a tower, but my
> theore=
> tical knowledge in this area is a bit lacking.
>
>
>
> Thanks for any thoughts.
>
>
>
> Tom Behler: KB8TYJ
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus=20
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
>
|
