Antenna Grounding?

KD7CJW

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Nov 11, 2021
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Hermiston, Oregon
I'm new here, so please be gentle with me.

I am going to be putting up some antennas at my house soon (GMRS, CB, 2m/70cm, and Scanner). The last time I put up a base antenna was roughly 48 years ago and I know things have changed!

Here are some questions I have. All of these antennae are omnidirectional, unity gain. NONE of them will have any more than 25 watts sent to them. ALL of them will be at the same height from the ground (roughly 20 feet).

My question are:
Should there be ground wires going to the antennas at the antenna or should I be doing all the grounding at the radios? I will be using a standard National Electric Code grounding rod and 10 gauge wire.
How far apart should the antennas be from each other?

Suggestions? Thanks!
 

krokus

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How are you mounting and spacing the antennas? (One tower, using two of the legs? Vertical separation? Separate poles, with one or two antennas each?)
 

mmckenna

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Take a look::
I haven't read through it all the way, but that's one of the better documents I've seen on the subject.

I'm new here, so please be gentle with me.
Welcome….

My question are:
Should there be ground wires going to the antennas at the antenna or should I be doing all the grounding at the radios?
Each antenna mast needs to be grounded.
Each coaxial cable needs to have a lightning protector where the coax enters the home, and those need to be grounded.
All your equipment needs to be grounded, also.

The document that @laidback posted covers that quite well.

I will be using a standard National Electric Code grounding rod and 10 gauge wire.
10 Gauge wire at minimum, larger if the runs are more than about 30 feet or so.

How far apart should the antennas be from each other?
As much as possible (more = better)
Here's why:
RF from a transmitting antenna can couple with the other antennas and put a lot of unwanted RF into the front end of the other radios. Get enough RF into the non-transmitting radio and you can damage them.
Even if you have them far enough apart to prevent damage when transmitting, there can still be enough energy to overwhelm the receiver and cause desensitization temporarily. That'll mean that the other radios won't receive while you are transmitting. Not the end of the world, but can be frustrating for some.

One challenge you have is that all your antennas will be at the same vertical height, which increases coupling. Having them at different vertical heights will increase isolation, which is good.

And in-band is going to be more problematic than out of band. As in: Your GMRS radio being UHF will create more issues with the UHF side of the dual band radio. Less issues with other bands, as in GMRS isn't going to be as much an issue with CB or VHF, etc.
So, where you place your antennas will make a difference. I'd recommend putting the dual band ham antenna as far away from the GMRS antenna as you can. CB won't be much of an issue, it's only 4 watts (right?) and far enough away frequency wise to not be as impacted.
You'll want to keep your scanner antenna far away from all transmitting antennas since the scanners tend to have wide open front ends with no filtering to keep strong RF out.


Sounds like you are on your way to a nice setup. Doing it right the first time makes a difference. Grounding is important. Some hobbyists overlook it, or assume that it'll never be an issue. Remember, it doesn't take a direct lightning strike to damage your radios, even a nearby strike can induce enough energy into the antennas and feed line to cause damage.

Other often overlooked thing…. Make sure you properly waterproof all your outdoor coax connections.
 

tommypickles

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Dec 19, 2002
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108
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Dwight Township ILL
Have a 5 foot tripod with three antennas on it this is what I have done. Run a 2 awg wire from the top antenna directly to ground rod. Using split bolts I grounded the other two antennas to the main run of 2 awg. At the entry point I have poly phasers that are grounded using 2 awg to the ground rod. I have two set ups like this on the roof and both have different ground rods, how ever they are bonded with a piece of 2/0 awg wire. Also it is bonded to the electrical system ground with a piece of 2 awg. The important thing is to use a short as runs as possible, bond all grounds and try to keep resistance to ground as low as possible. Budget will dictate most of this.
I hate to say this but grounding questions will bring different answers from everyone you ask, none are wrong, just we all have differnt installations and circumstances as well as $$. Do your homework and work with what you have.
 

KD7CJW

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Messages
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Location
Hermiston, Oregon
How are you mounting and spacing the antennas? (One tower, using two of the legs? Vertical separation? Separate poles, with one or two antennas each?)
Each antenna will be on its own mast, roughly 2 feet into concrete, below the dirt line, and supported at the roofline with a 4-inch standoff bracket.
 

KD7CJW

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Joined
Nov 11, 2021
Messages
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Location
Hermiston, Oregon
I haven't read through it all the way, but that's one of the better documents I've seen on the subject.



Welcome….



Each antenna mast needs to be grounded.
Each coaxial cable needs to have a lightning protector where the coax enters the home, and those need to be grounded.
All your equipment needs to be grounded, also.

The document that @laidback posted covers that quite well.



10 Gauge wire at minimum, larger if the runs are more than about 30 feet or so.



As much as possible (more = better)
Here's why:
RF from a transmitting antenna can couple with the other antennas and put a lot of unwanted RF into the front end of the other radios. Get enough RF into the non-transmitting radio and you can damage them.
Even if you have them far enough apart to prevent damage when transmitting, there can still be enough energy to overwhelm the receiver and cause desensitization temporarily. That'll mean that the other radios won't receive while you are transmitting. Not the end of the world, but can be frustrating for some.

One challenge you have is that all your antennas will be at the same vertical height, which increases coupling. Having them at different vertical heights will increase isolation, which is good.

And in-band is going to be more problematic than out of band. As in: Your GMRS radio being UHF will create more issues with the UHF side of the dual band radio. Less issues with other bands, as in GMRS isn't going to be as much an issue with CB or VHF, etc.
So, where you place your antennas will make a difference. I'd recommend putting the dual band ham antenna as far away from the GMRS antenna as you can. CB won't be much of an issue, it's only 4 watts (right?) and far enough away frequency wise to not be as impacted.
You'll want to keep your scanner antenna far away from all transmitting antennas since the scanners tend to have wide open front ends with no filtering to keep strong RF out.


Sounds like you are on your way to a nice setup. Doing it right the first time makes a difference. Grounding is important. Some hobbyists overlook it, or assume that it'll never be an issue. Remember, it doesn't take a direct lightning strike to damage your radios, even a nearby strike can induce enough energy into the antennas and feed line to cause damage.

Other often overlooked thing…. Make sure you properly waterproof all your outdoor coax connections.
"Other often overlooked thing…. Make sure you properly waterproof all your outdoor coax connections."

I forgot to ask about that. What do you use?
 

Homeboys-Scanna

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2,697
A lightning protector (which may also called a lightning arrestor) is basically a barrel connector that adds a 3rd connection screw to physically connect your 10 or 6 gauge copper wire down to a ground rod. So your piece of coax connecting the radio to the antenna will basically be cut in half, new connectors installed, so you can insert the lightning arrester. The arrestor should be placed outside, just before the 2nd run of coax enters the inside of the structure.
 

mmckenna

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"Other often overlooked thing…. Make sure you properly waterproof all your outdoor coax connections."

I forgot to ask about that. What do you use?
I don't buy them off e-Bay, but here's a great price on a similar kit to what I use at work:
The 2" wide electrical tape, self amalgamating butyl rubber tape, and even the coax grounding kit, all for $10 + shipping.

or

You can buy brand new kits here:

Be wary of anyone that tells you that you don't need to waterproof your outdoor connections, or those that claim "I've never done it and never had a problem". Confusing luck with skill/knowledge is always a bad thing. While some coaxial connector designs are water resistant (N, DIN connectors, etc), no one in the industry trusts that alone. Industry standard is to always seal the outdoor connections.
 
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