Jack Painter wrote:

"§ Dr. Artaud §" wrote
Every year, I fear the spring and summer. I have a random wire antenna
that traverses one side of my property, the wire extending about 70 feet.
No lightning protection. I remove the wire from the radio when I am at
home
and I know that I storm is coming. But when I am at work, and storms
happen
unexpectedly, the radio stays connected. Even protecting the radio from
the
static of a nearby lightning strike by disconnecting it doesn't protect
the
house from the results of a strike to the wire.

I would like to switch to a V shaped antenna, perhaps it is what they
refer
to as an "inverted V" extending from a central point on my house to both
sides of the property. I would like to feed the antenna with coax, so as
to
reduce the likelihood of household interference. The feed would only be
about 20 feet long. I would have trouble grounding it at the apex of the
V,
since that would be on the house itself and the patio is directly below
it,
providing much cement but little ground to place the rod. Though I could
drill the patio, I am unsure of the pipes below it.

My lot, at least as far as the usable area for the antenna is concerned,
would be about 30 feet wide and 70 feet long, with the elevation of the V
to be approximately 12 feet from the ground.

Can anybody conceptualize an antenna that I can use, with lightning
protection, and provide links to it? Is anybody using something similar?

Thanks for any help.

Dr. Artaud

The Inverted-vee is a center (or off-center) fed dipole with it's ends lower
than the feedpoint. Rarely a desired design, it usually results from being
unable to elevate both ends equal to the feedpoint of a half wave dipole. It
nonetheless works fairly well and is a "complete" antenna, requiring no
grounding. It is not a vertical antenna as Ace suggested.

They are generally vertically oriented, therefore the 'inverted vee'
designation.

dxAce
Michigan
USA



However, for lightning protection, all antenna feedlines regardless of
antenna type should be shield-grounded if using a coax feedline. The first
point of this shield-grounding should be as near as possible to where a
grounding conductor/jumper/bond can be first located. That means on the
tower if the tower is the feedpoint of the inverted-vee, or where the
feedline first reaches earth-grade at 90 degrees from the feedpoint. Coax is
again shield-grounded at the ground rod used as the shack's single point
ground. A surge protector or oft-called lightning arrestor is then used to
protect the equipment where the feedline originates.

If it is physically possible for the antenna to take a direct lightning
strike (not a probability if nearby objects are higher) then the feedpoint
shield ground is the primary discharge point, and should have a network of
ground rods connected by heavy (#4 or larger copper wire or wide copper
straps). Even if a direct strike is not possible, indirect strikes
(flashovers from a nearby tree or other higher object) are still possible,
and the first shield ground remains of primary importance in the protection
scheme. Feedline running along the earth or even buried a few inches in the
earth are also subject to magnetic and capacitive coupling of lightning
strikes nearby. The near surface of earth carries 10's of thousands of volt
potential from strikes as far as 100 yards away. Any ground system that is
connected to equipment in the shack has the potential to reference these
voltages right onto the grounded equipment cases in the shack. This is why
proper bonding of inside equipment and all grounding systems is vital to
prevent this ground potential rise from exiting the equipment through AC
power connections out the rear of the equipment. See my site for further
information about bonding and grounding antennas and equipment:

http://members.cox.net/pc-usa/station/ground0.htm

Best regards,

Jack Painter
Virginia Beach, Virginia