B
BOOTY MONSTER
Guest
why is it that lightning rods help protect a house from a lightning strike but base antennas dont ?
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http://www.ira.usf.edu/cam/exhibitions/1998_12_McCollum/supplemental_didactics/21.Uman2.pdf
One of many answers. This may help you understand the specific function of a lightning rod.
One of many answers. This may help you understand the specific function of a lightning rod.
Because your electrical service is not connected to earth through the base antenna's path to earth.
There is a path to earth on every power pole or underground terminal before the transformer and after the transformer at your house.
If your services neutral is broken and you do not have a path to earth at your house get ready for a large fire ball.
B
BOOTY MONSTER
Guest
if the antenna is connected/bonded to the homes electrical system ground rod through the mast and a heavy ground wire isn't the electrical service connected to earth through the base antenna's path to earth ?
No, they are both bonded to earth at a common point and will not protect your home's electrical service.
A properly installed and grounded antenna system WILL protect a house from getting hit. It offers what is called a cone of protection. The tower/antenna will take the hit instead of the house. What usually happens however is that the system is not grounded properly and damage results. When you have multiple ground points and not a single point ground you can have a voltage develop between the ground points when the electrical pulse travels through the ground (earth). This causes the ground system to develop a strong current flow that takes out electrical gear.
B
BOOTY MONSTER
Guest
"When you have multiple ground points and not a single point ground you can have a voltage develop between the ground points when the electrical pulse travels through the ground (earth). This causes the ground system to develop a strong current flow that takes out electrical gear."
are you saying there should not be any additional ground rods for the antenna ? just the one for the electrical panel/service ? ..... and use heavy copper wire to bond the antenna/mast to that one ground rod ?
the article pro 151 linked to had a cone of protection illustration just as you described
are you saying there should not be any additional ground rods for the antenna ? just the one for the electrical panel/service ? ..... and use heavy copper wire to bond the antenna/mast to that one ground rod ?
the article pro 151 linked to had a cone of protection illustration just as you described
When you have multiple grounding points in "close" proximity the chances of the capacitance rising in the earth is greatly increased.
6 to 8 feet of space between ground points should be sufficient to stop this in most soils.
If you use the same ground point chances are you are safe, I've had mine that way for several years now and seen many lightning storms.
Being in the wrong place at the wrong time is your enemy so what are your chances?
6 to 8 feet of space between ground points should be sufficient to stop this in most soils.
If you use the same ground point chances are you are safe, I've had mine that way for several years now and seen many lightning storms.
Being in the wrong place at the wrong time is your enemy so what are your chances?
"When you have multiple ground points and not a single point ground you can have a voltage develop between the ground points when the electrical pulse travels through the ground (earth). This causes the ground system to develop a strong current flow that takes out electrical gear."
are you saying there should not be any additional ground rods for the antenna ? just the one for the electrical panel/service ? ..... and use heavy copper wire to bond the antenna/mast to that one ground rod ?
the article pro 151 linked to had a cone of protection illustration just as you described
What I meant is that all grounds should be tied together at one common point. Any ground rods at the tower base, main station ground, and the electrical service entrance ground should all be tied together at one point. This ensures that all grounds are at the same voltage potential in the event of a strike. Even if the ground reference point is raised to a couple hundred volts in a strike no current will flow between two ground points because ALL ground points are tied together and will be at the same voltage potential. I know it seems hard to think that a ground point can actually have a voltage above ground or that current can flow between two DIFFERENT ground points but that is what happens when a pulse from lightning travels through the earth. A ground rod at the base of a tower that is struck will have hundreds or thousands of volts on it for a few milliseconds until the energy is absorbed by the earth.As the pulse travels thru the earth it takes time to reach the next ground point which may be at the other side of the house ie: electrical service entrance. It seems like it all happens at once but even milliseconds or microseconds at a few thousand volts is enough to destroy gear.
House ground layouts
It's not so much the capacitance of the earth unless you mean the capacity (ability) of the earth to absorb energy. In that case yes, it takes time for the energy to be absorbed and the more rods the more energy conducted to earth. When rods are close together the earth literally is overloaded with electrons and is saturated causing it to take longer to absorb the energy. When rods are spaced further apart it allows the area immediately surrounding each rod to be better able to absorb the lightning energy.
DC grounded antennas work as lightning rods.
Once.
That pretty much depends on the method of DC grounding. A small coil to ground is going to vaporize while an antenna that is meant to be solidly grounded at the mounting point point will survive over and over again. Commercial FM antennas are DC grounded and take several hits every year on average. I watch one of my FM towers get hit five times one storm and that was after the initial hit that took us off the air. Lots of ham antennas get hit and survive. Again, it all depends on the grounding method.
DC grounded antennas work as lightning rods.
Once.
AND poorly grounded antennas act as station vaporizers