<italic><color><param>0000,0000,0000</param>> Lightning has been mentioned as a
possible cause of arcs - yet almost
> immediately discounted. I would like to raise the question of whether the
> dismissal should be quite so quick..
</italic></color>Lighting generally leaves many calling cards, besides damage
to
one rather large component way down deep in the system.
It isn't that lightning can't cause damage, its just that you are many
times more unlikely to NOT find your telephone, TV set, VCR,
power supply diodes, antenna switches and relays, loading
capacitors, and receiver front ends damaged along with the
bandswitch or other large components.
So the lightning itself likely won't supply the energy that does the
damage, unless it also damages other things. That isn't to say a
high charge level can't initiate an arc.
<italic><color><param>0000,0000,0000</param>> I understand little about
discharge from the atmosphere - but I have felt
> large enough voltage to shock me by simply touching a 30 foot wire antenna
> with no more than a dark cloud passing over. And, I built an scr operated
> burglar alarm years ago with a closed loop operating about 2 feet off the
> ground. It picked up enough energy from dark clouds that the alarm would
> fire every time a dark cloud passed overhead.
</italic></color>I have a 160 meter dipole at 300 feet. Even on calm days when
I
switch to it, I see my peak reading wattmeter needles kick way up
as the feedline and antenna discharge.
Someday I'll put a choke or leak resistor on it.
<italic><color><param>0000,0000,0000</param>
> So, the question is, when the amplifier is actuated and relay closed, is
> it possible that a static discharge returns down the antenna - and while
> not of sufficient voltage to blow a hole in your roof, might add to the
> existing voltage to create an arc which otherwise would not occur.
</italic></color>Absolutely. That's the bad thing about an arc in air, once you
ionize the air the arc continues even at much lower voltage.
<italic><color><param>0000,0000,0000</param>> Perhaps the rf choke that all
good amps have installed from antenna to
> ground would address this and short all to ground. This might apply to dc
> - but the rf choke might appear as a high resistance to the static.
</italic></color>It depends on the slew rate of the voltage. If the slew rate
is high, it behaves like RF so far as components are
concerned.<italic><color><param>0000,0000,0000</param>
> Could this be one of the causes of the arcs?
</italic></color>Could be. There is a lot more energy there than in a photon
from
Gamma V.
<nofill>
73, Tom W8JI
w8ji@contesting.com
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