"MC" wrote in message
...
dnoyeB wrote:
wrote:
What is the proper and best way of grounding a tv antenna at the top of
a 40' tower? I have a cottage on lake huron, and the tower is going to
be the highest metal point for quite a few hundred feet. I am
concerned about damage when lightning hits the tower or antenna. Also-
Should a grounding jumper be run around the rotator to ground the
antenna and mast? Thanks
grounding the tower will just make it more attractive to lightning.
However, it will protect you since the lightning will enter the ground
and not the house.
You probably need a lightning rod or something to attract or disipate the
lightning, which will also be grounded.
should have the antenna part lower than the highest point of the grounded
tower with lightning rod on top of tower and sufficient ground cable to
sink the current into the ground (there is a formula, can not remember)
The antenna is shielded due to an umbrella effect of the higher point of
the lightning rod.
My gosh, such misinformation.
An antenna still has a good chance of getting hit by lightning directly even
if there is a lightning rod nearby. Lightning is random by nature.
The tower is already grounded by virtue of it probably being bolted to a
concrete pad at ground level and being made of metal. Grounding it more will
not increase the electric field at the top.
Ground wire for the antenna provides a lower impedance path to ground which
the majority of the current will follow. A direct strike can still send
current through other paths. Sufficient sizing of the ground wire will
minimize the current in these paths. This obvoiusly allows you to control
where that current flows instead of leaving it to nature at the base of the
antenna.
All you need is a spark gap, a ground wire and a ground rod. The basic
diagram is included with the instruction manual of every consumer
electronics equipment that connects to an antenna like a TV or VCR for many
years. There are also off the shelf grounding kits anywhere they sell
antennas, complete with instructions (you may have to buy a seperate
grounding rod)
Grounding of all the splitters (particularly the first one) adds a measure
of additional protection for you and your equipment. You can ground the
shield of the cable anywhere you want, the center conductor is floating (WRT
DC current) and connected mainly to the transformer windings in the
splitters with no actual (DC) direct path between the antenna and the TV.
Current in lightning will fuse this path open in a flash, most current will
enter the house via the shield which may be DC connected to the antenna.