Do I really need to ground my elevated Gp antenna?

[cjruger]

Right now I'm running no ground on my homebrew 5/8 GP. its about 35 ' up in a pine tree. I do have a small copper pipe driven in to the ground rith outside my window with a wire I attach to the outer connector of coax right at the back of radio for stray RF. Not sure if this actually does anything or not. I usually just unhook the coax ad put in a glass canning jar in case of lightening strike. I figure the antenna will be destroyed regardless if it is grounded or not and its away from the house in a tree. . I was just reading a write up on how grounding with minium 3 copper rods from the elevated gp antenna will improve its performance aside from lightinging saftey. also adding full wave length radials on the ground going away from the ground rods will help with reflection.
Any truth to this and is it worth doing aside from a saftey standpoint? I have read about as much as i can find on this and I am still confused about weather It is needed or not.

 

[Tallman]

The AARL handbook has the answer to that. The triple ground rod is for the triangular towers like Rohn. For lightning protection the more paths to ground that are out side of your dwelling/radio shack the better. Do not solder the wires to the ground rods as this will melt if a lightning hit occurs.
Also this helps reduce receive noise.

 

[Robb]

Think this out for a moment . . .

A bolt comes down that has 100k+ amps of current because the ground field on the surface of the Earth has the greatest attraction due to a vast collection of opposite charges. Over a distance of a few miles.

Just how much current can an antenna itself pass before it becomes a fusible link?
Just how many strikes/pulses are occurring in that strike?
Most important; where is the greatest paths of potential flow and the least path of resistance?

To have an antenna that can survive a strike, it would first need to pass that vast current by itself. Next, as this current continues towards the ground/opposite charge; just what is there to conduct the greatest volume of current flow?

If that antenna is in a tree; then the tree itself will get flow through as it follows the least path of resistance. If there is more water in the tree than there is on its surface; then the tree will explode because that water will superheat, turn to steam, and expand at a rapid rate. If there is anything that will impede this flow of current; then it will heat up and be destroyed.

So if one can provide a large gauge conductor from the antenna to the ground rods that can handle that much current; then the current will want to follow that path and may save the tree.
Not talking about using some 10ga wire - either.

There is also an electro-magnetic pulse ('EMP') created by a lightning strike that will damage radio equipment; so that gear will need to be well grounded. There will also need to be isolation from the coax; so that also will require a sturdy ground path.

At least that is as much as I understand about this issue.
If you live in areas prone to lightning strikes; then it is best to understand all that you will face.

 

[cjruger]

Think this out for a moment . . .

A bolt comes down that has 100k+ amps of current because the ground field on the surface of the Earth has the greatest attraction due to a vast collection of opposite charges. Over a distance of a few miles.

Just how much current can an antenna itself pass before it becomes a fusible link?
Just how many strikes/pulses are occurring in that strike?
Most important; where is the greatest paths of potential flow and the least path of resistance?

To have an antenna that can survive a strike, it would first need to pass that vast current by itself. Next, as this current continues towards the ground/opposite charge; just what is there to conduct the greatest volume of current flow?

If that antenna is in a tree; then the tree itself will get flow through as it follows the least path of resistance. If there is more water in the tree than there is on its surface; then the tree will explode because that water will superheat, turn to steam, and expand at a rapid rate. If there is anything that will impede this flow of current; then it will heat up and be destroyed.

So if one can provide a large gauge conductor from the antenna to the ground rods that can handle that much current; then the current will want to follow that path and may save the tree.
Not talking about using some 10ga wire - either.

There is also an electro-magnetic pulse ('EMP') created by a lightning strike that will damage radio equipment; so that gear will need to be well grounded. There will also need to be isolation from the coax; so that also will require a sturdy ground path.
Ya i guess. 3 6'copper rods and 40' of heavy ground cable is big $$ to save the tree.
At least that is as much as I understand about this issue.
If you live in areas prone to lightning strikes; then it is best to understand all that you will face.

How many amps of the 100k could possibly go thru the coax? Seems like it would just melt. I usually unhook the coax so equipment is not attached. So what am i saving from lightining?

 

[Tallman]

The main idea is get the lightning into the ground and not into your equipment. I disconnect my antennas when going on vacation or if bad weather is expected in the area.

 

[The DB]

Electrically speaking, a ground plane antenna will perform equally well weather earthed or not. There are some benefits, such as less static noise in some circumstances, and there is a new path you need to ensure no antenna mode currents are flowing on as such currents will push your radiation pattern up to a higher angle.

When it comes to saving the antenna in the event of a direct lightening strike, or even a near miss, well, not going to happen, sorry. The best you can do is minimize the chance of a lightening strike as much as possible, which proper earth grounding of the entire antenna (not just the ground plane) will do. Proper earth grounding will also go a long way in saving your radio in the event it is hooked up when a strike hits.

Also, stay away from putting the coax end in a mason jar, it is not a good idea. If you want to do something to the end of the coax you simply attach a connector that shorts the inside wire and shielding of the coax. If you grounded said coax properly this extra measure isn't needed, but it is 1000 times safer than putting the end of the coax in a mason jar. A bolt of lightening has the energy to travel through over a mile of a very good insulator, if you think that a quarter inch of glass, if that, will do anything at all to stop it from going where it wants you are sadly mistaken, and are adding the unnecessary risk of shattering glass. Use at your own risk, and the risk of anyone else who might be present when a strike actually occurs.


The DB

 

[Robb]

Pulses in slow motion:



Sometimes lightning goes from ground to cloud too, if the stored ground potential is higher than the clouds have:

 

[cjruger]

One more question, if the ground cable/wire is close to a wave length of my operating frequency, will it radiate signal or give me signal loss? After all it will be attached to the radials which are all the same 1/4 wave length, creating a 5 radial going straight down at almost exactly 1 wave length

Update!! It's grounded !! Used 6ga stranded with a long 6 or 7' copper coated steel rod. I didnt realize it was coated until I started pounding, oh well better than nothing

 

[Beetle]

Right now I'm running no ground on my homebrew 5/8 GP. its about 35 ' up in a pine tree. I do have a small copper pipe driven in to the ground rith outside my window with a wire I attach to the outer connector of coax right at the back of radio for stray RF. Not sure if this actually does anything or not. I usually just unhook the coax ad put in a glass canning jar in case of lightening strike. I figure the antenna will be destroyed regardless if it is grounded or not and its away from the house in a tree. . I was just reading a write up on how grounding with minium 3 copper rods from the elevated gp antenna will improve its performance aside from lightinging saftey. also adding full wave length radials on the ground going away from the ground rods will help with reflection.
Any truth to this and is it worth doing aside from a saftey standpoint? I have read about as much as i can find on this and I am still confused about weather It is needed or not.

That lightning bolt has traveled several thousand feet and maybe a few miles through air to get to the ground. Exactly how much do you think it's going to be deterred by 1/8" of glass?
Is "grounding" needed? Lightning protection certainly is. This forum has a ton of information about how to do it the correct way (hint: canning jars are not part of the correct way.) You might get lucky and never suffer a direct or near-direct strike. On the other hand, you might suddenly end up without a rig or a house to put it in. Your call.