On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11"
wrote:

Hello:

Have been reading up on lightning a bit, and it certainly
is a confusing subject.

Let's say I have an Inverted-L or a Sloper in the yard (receiving only).

If a lightning storm is in the vicinity, obviously the best protection
possible is to just disconnect the radio from the antenna. No differences
of opinion here, I would imagine.

But, as a more or less theoretical question, to minimize the possibility of
lightning hitting the antenna at all, or inducing large voltages in it, is
it better to just leave the now "floating" antenna alone, or is it better to
ground one end of it ?

Why ?

You have to think carefully about what you are trying to protect.

It seems to me that in the event of a lightning stroke in the near
vicinity of your antenna, large voltages will be induced in the
antenna wrt "ground", whether or not your antenna or its support
structure features as a streamer, or takes the current from a leader.

That voltage may be sufficient for insulation breakdown, and charge
will flow to ground via some path, not necessarily of your choosing.
Substantial physical damage may occur where insulation breaks down,
the path of the side-flash current may result in further damage to
persons or equipment.

If you make a substantial connection from the feedline to some thing,
you have some degree of control over the path that the discharge
current flows. Properly chosen and implemented, that might be better
than doing nothing, but if poorly designed or implemented, it could be
worse than doing nothing. Side-flash can still occur where you have
provided a path to ground.

Very often, the target of effective lighting protection of radio
installations is minimisation of voltage drops or potential
differences internal to an installation as a result of lightning
discharge current rather than trying to minimise the voltage to
"ground" resulting from the current.

Owen
--