Base Antenna Grounding

[Drifter]

Sorry if it had been discussed before,, so here goes.... What is the best way or ways to ground a base station antenna??? :?: and can someone explain RF grounding and Lighting protection grounding.??? :?: I am in the process of grounding my system and would like to do it the correct way. 8)

Drifter

 

[Peddler]

Some good info here;
http://www.smeter.net/grounds/grounds.php

 

[Moleculo]

And also try this thread:

forum.worldwidedx.com/viewtopic.php?t=6729

 

[Drifter]

Thanks for the help... This site rocks.

 

[CDX197]

This site rocks.

We know! And if you dont want to worry about lightning move to Alaska. All you will get is snow. :roll:

 

[AkBowtie]

This site rocks.

We know! And if you dont want to worry about lightning move to Alaska. All you will get is snow. :roll:

Hey!! We get Lightening Too!! More snow than Lightening, but we do get lightening. Melts our Igloos with every strike

AK295
Blue Goose
Anchorage Alaska
27.385/27.555 lsb

 

[freecell]

http://forum.worldwidedx.com/viewtopic.php?p=40669&highlight=lightning#40669

 

[DXman]

Hello Blue Goose,
Great state you live in there.....worked up there off and on for 17 years.
Welcome to a great forum!
------------------
DXman

 

[SmackDown]

Grounding

I'm putting up an Astro Plane which is grounded through the mast which is going to be mounted on a chimney mount. My home is 2 stories and since my basement is above grade the overall height is closer to 3 stories. Then I have 20' of mast to place in the chimney mount. I figured 100' of coax is enough to go from roof to the basement with a little extra to spare. I'm thinking I'll cut the coax before it enters the building and install a groundable barrel or an iceradio http://www.iceradioproducts.com/3.html or polyphaser arrester / suppressors or is any one of those 3 options viable ? I'll use a coax (jumper), mount the arrester to the chimney mount then the remaining coax can travel to the radio room ? Then I'll run two ground wires down to the grounding rod. One from the mast and the other from the inline arrester. Any thoughts on this ??? Also what guage of wire is suitable to run from the arrester and mast to the grounding rod ? :twsted

 

[Marconi]

This sounds familar, but you have to get the PolyPhaser or whatever you use close to the earth. The idea is to establish as low resistance to ground as possible from the point of the device to the earth. And close, short, fat, heavy, and big means low resistance.

By the time you get your ground line from the PP to the earth ground when mounted up high like you suggest, your resistance may be well above that of the coax and then the PP will not have protected you as intended. In order to redirect current you must provide it an alternate path from a point close to the earth, a path of less resistance. The longer that path is the less effective it is and that is what I think you are suggesting by putting the PP up on the roof tower and then running a line down to ground rod(s).

All the coax (inside and out) must be protected as lightning current will be all over that coax. If I were you and had a roof mount I would keep that wire from the antenna mount going directly to a ground rod of its own. Just insulate it from the house. And I would also have the coax run thru the PP that was attached to another, maybe three ground rods spread out a bit down below the antenna just so the PP would have a good low resistance point to dump the current into. Put the PP right were you want it to work, redirecting the hit.

 

[SmackDown]

Marconi,
I've looked at PP even spoke to their tech and he never said what you told me about having that arrester as close to the ground as possible. I looked at another site http://www.iceradioproducts.com/3.html (click on coaxial)
and see the ice product has a different design than PP. Your last message to me states that I get that arrester as close to the ground as possible before the coax enters my basement for as short a run as possible from the arrester to the ground rod. Then you mention 3 rods.. I had to drill through concrete to get the 1 rod in which is a 10'. Only 8" of that rod is above grade. Isn't that enough ??? :shock:

 

[Marconi]

Well Smackdown, of course I could be wrong. This is just my opinion. If the devices instruct you to put the thing close to the antenna and not to the earth then follow their instructions. It just does not make sense to me to do otherwise, but I have been wrong before.

The only idea about having more than one Cu' clad ground rod is that more provides lower resistance at termination than one ground rod. Remember the bigger, fatter, shorter, rule. There are some ideas about keeping these ground rods a bit apart, like maybe 8' in the case of 8' ground rods. Of course they should all be physically connected using heavy connectors of similar or non-corrosive materials and protected somehow from the affects of earth on the connections. You know what happens to a car battery when the connectors become corroded?

These systems depend on maintaining a low resistance at the redirecting point to earth as I have already said. This low resistance may be hard to maintain unless well designed and protected from soil. So, I believe the best line of defense is to disconnect the feed line and hook it directly to a bulkhead that is outside and directly connected to a ground rod system that keeps it away from all conductors into the home, even those underground for about 8’-10’.

In all cases though, install as instructed by the manufacture.

 

[Captain Kilowatt]

The best place to ground any cables or lightning arrestors is at the point of entry to your house etc.This keeps induced currents to a minimum.You can also install an arrestor at the antenna if you want too but it is redundant and the long run of ground cable may well offer a higher resistance that the coax itself as Marconi suggested.My main concern with your mounting choice is the chimney mount with a 20 foot mast.It will have to be guyed or it will break the mortar and bricks in the chimney.Also God forbid but if lightning did strike the antenna you can probably kiss your chimney good bye.The heat from a strike can and will turn the moisture in the brick to steam instantly and the resulting explosion will blow the bricks apart and topple what is left of your antenna/mast. I am not a fan of chimney mounts as you can tell. :?

 

[W5LZ]

FWIW

Grounding wire should be large (as Marconi said). The longer the run, the larger it gets until it gets rediculous.
The 'smart' way of thinking about it is that anything between the arrector and 'clear blue sky' will be fried with a lightning strike. The stuff between the arrestor and the radio probably wont (no absolutes with lightning!). If you're lucky and stuff isn't fried then you are ahead.
Ground rods. Current/voltage has to be dissipated in dirt to get rid of it. That means that the more conductor area that you have, the better that dissipation. Going 'down' just isn't that important, going 'sideways' works just as well if not better. It doesn't matter how long that groundrod is, the current is only going to go so far and no deeper (conductivity/frequency/disipation thingy). Laying the ground rod horizontally just below surface level will work just as well as driving it straight down, and it will disipate just as much current. So, ground radials tend to work better than ground rods. Not as simple/easy to get in the ground, but there ain't no 'easy' way to do anything 'right'. Besides, it really isn't that difficult, it's just different.
- 'Doc

PS - To make it even more interesting just remember that currents flow in ~both~ directions in a ground system. It can come 'up' that ground conductor too...

 

[SmackDown]

Okay, instead of mounting the arrester at the chimney mount, I'll lower it. Nothin's easy anymore. I'm afraid to anchor any arrester to the wooden framework around a window that leads into the basement but it's either that or try to drill through a stone foundation . And I have driven the groundrod vertically because to do it horizontally would mean removing and replacing quite a few slabs of concrete. The thought of that gave me grey hairs . Maybe I'll drive another groundrod in within a foot of the first one and then hope for the best. Am not concerned about the weight of the Astroplane on the chimney mount, it's only 4 lbs. Just want to do the best I can to stay safe.