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Author Topic: Station rf ground.  (Read 777 times)
K5BDH
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« on: December 29, 2009, 09:42:44 AM »

I am working on installing a different type of antenna out back of my house and have a couple questions in regards to station/rf grounding. Im still a newbie at all of this.

1)My house has the 3 prong electrical outlets that are grounded in the back of the house to a ground rod. Is it possible to run an additional ground wire out of the plug and connect to the ground screws on the back of my radio/ps to help with grounding the new antenna im putting up or am I nuts even considering this?

2)I have a 8' ground rod that I may drive into the flower bed out front and have to run a 10ga solid copper wire or a 10' section of flat copper braid through the window to tie into it. I know I probably need at least 2-3 of them for a proper ground.

Thanks.
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W4LWZ
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« Reply #1 on: December 29, 2009, 09:52:59 AM »

You have the right idea about grounding.  I would not trust using the ground pin in a wall outlet though.  Pound in 2-3 ground rods outside the shack and connect them together, then run a heavy (#6) wire from the ground rods you installed to the ground rod at the power service entrance.  When you install the ground rods, space them at least twice their length apart.  If you install 8 ft. rods, space them at least 16 ft. apart.
This will give you an adequate ground system.
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AA4PB
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« Reply #2 on: December 29, 2009, 09:54:27 AM »

No, it is not acceptable to just run a wire out of the plug grounding pin to the radio chassis. That long run of cable to the electrical panel won't provide an RF ground anyway.

What kind of antenna do you have? Most balanced antennas like a center fed dipole don't require an RF ground at all. Lightning safety does require grounding the coax shields to one or more ground rods at the building entrance and the NEC (National Electric Code) requires that grounding system to be tied to the building electrical grounding system via at least a #6 conductor.

There are three types of grounding: 1) the electrical safety ground (3rd pin on the plug), 2) lightning safety (single point ground at the building entrance), and 3) RF ground if required by your antenna (most often a number of radials buried in the ground near the antenna).
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K5BDH
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« Reply #3 on: December 29, 2009, 10:30:38 AM »

I am setting up one of the Buckmaster 7band ocf antennas. My stations is in the front of the house and the antenna will go up in a tree about 35-40' above my back fence. Long coax runs for sure, just not any way around it. I currently use two 100' premade rg8x cables running to my end fedz. How would you go about running a #6 conductor from the cable shield to the house ground rod at the back of the house? My guess is using something like a polyphaser where the sections of coax join then running a wire from that to the house ground rod. Either that or using one of the MFJ antenna feed through attic vent panels that have the ground connection on it. I have one of the Alpha Delta B series rf coax switch that has the arc plug that you can run to ground. I ended up not needing it with my current cables but I guess if it actually works I can use it to ground the cables on the backside of the house before they come into the attic.
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AA4PB
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« Reply #4 on: December 29, 2009, 10:45:36 AM »

Normally you want to bring the coax down near the ground before going into the house so that you have a short wire to the ground rod. One way is to mount Polyphaser surge protectors on a metal plate and connect the coaxes to them. Connect the plate to your ground rod and to the electrical service ground rod or the ground wire comming from its ground rod.
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AI7RR
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« Reply #5 on: December 29, 2009, 11:14:21 AM »

Most important: DO tie all of your grounds/ground rods together.
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KB9CRY
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« Reply #6 on: December 29, 2009, 01:09:43 PM »

Read up on the different types of grounds. You obviously are confused since you are mixing up the terms for them.  Lightning/safety grounds and RF grounds are two totally different and separate things.
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K8KAS
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« Reply #7 on: December 29, 2009, 01:10:32 PM »

Wake up guys, an 8 foot ground rod IS NOT a RF Ground.
A good copper or SS plate connected to 15 or 20 radial
wires 30 or more feet will get you a basic RF ground.

I say again basic. This 8 foot ground rod stuff drives me crazy.

PS... keep the connection from the ground plate to your station as short a you can.

Yes you will have to do some work but it's worth it.. Denny K8KAS 73
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WA3SKN
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« Reply #8 on: December 29, 2009, 01:30:39 PM »

There are three types of grounding...
The DC ground, the safety (AC) ground, and the RF ground.  Know the reasons behind the grounding.  Both the Polyphaser and ICE websites do a good job of describing this... very good reading.  And will give you ideas about just what is needed.
73s.

-Mike.
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K5BDH
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« Reply #9 on: December 29, 2009, 01:45:06 PM »

hum. maybe I will just stick with my current end fedz antennas. They work and being able to get on 80m with all the ground requirements just isnt worth it. Would need a couple acres to run all the wires required for these kind of ground-radials or whatever the proper term is for it.
thx for the replies.
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AB4VV
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« Reply #10 on: December 29, 2009, 05:39:10 PM »

Don't give up. Try your antenna and feed line Without any ground system and just see if you do indeed have an RF problem! Most likely you will not if the antenna is far enough away!

Whatever you do DO NOT connect anything to your wall outlets thinking you can ground to them. Thats scary!
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N7ZM
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« Reply #11 on: December 29, 2009, 05:54:35 PM »

There is a huge difference between a RF ground and ground on house electrical system. Too many get confused and think they are the same, they are not.
To properly deal with the two you need to do some serious reading on grounding on electrical systems and RF grounding.
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K9KJM
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« Reply #12 on: December 29, 2009, 11:35:00 PM »

You have received some very good answers so far pointing out that there are a number of different types of ground systems to do different things.

As correctly pointed out, Station RF ground needs counterpoise "radial" type wires, As ground rods do little to nothing for station RF ground.

For decent lightning protection, You need the ground rods, Which as also correctly pointed out should be spaced about twice the distance apart as the depth.

Note that by using heavy enough bare copper wire, You can easily incorporate BOTH types of ground system into one. The #6 bare copper from your single point ground going out to the properly spaced ground rods will be the "counterpoise" system! (As you get further out and away from your tower or mast/single point ground you could go with smaller size wire to save costs, And space rods further apart)

For some good info on lightning protection:

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

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W8JI
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« Reply #13 on: December 30, 2009, 04:53:20 AM »

Try reading this and related links:

http://www.w8ji.com/ground_systems.htm


The amount of RF ground you need really depends on the antenna system and the other equipment in the shack. If everything is working right with coax or a two-wire feeder you should not need an RF ground at all!

You only should really need an RF ground if you have a Marconi type of antenna, or a single wire feeder. A vertical for example needs a ground, as does a longwire. But it is always best to do that grounded outside and away from the house.

I agree with K8KAS. A six foot ground rod sucks as an RF ground. Around here the RF resistance of a six foot rod on 160 meters, even with moist soil, is about 50-100 ohms. Fortunately unless we run a end-fed antenna of some sort there really is very little reason to have a "RF ground".

The safety ground and lightning ground is a different issue.

Tom
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KX8N
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« Reply #14 on: January 02, 2010, 11:43:06 AM »

"Wake up guys, an 8 foot ground rod IS NOT a RF Ground. "

True, but he's talking about installing an ofc DIPOLE, which doesn't need an RF ground.

I think we need to know why he feels he needs to install a ground system.
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