Scanner/Radio Install in Home

krokus

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#5
I watched a YouTube video of a guy that had this mount and he didn't ground it.
Any antenna you install outside your home needs to be grounded per the National Electric Code. Doesn't matter if it has a grounding point or not.

There's a lot of stupid stuff on YouTube, so not surprising that there's someone telling you to install an antenna outside your home and not ground it.

Ultimately it's your choice to ground or not ground the antenna. The National Electric Code exists for a reason, and it's not there just to make hobbyists life harder.
 
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#6
How can I ground the antennas that I would put on the below?

https://www.cheapham.com/tram-1465-nmo-land-mobile-base-ground-plane-kit/

Trying to think of the best way to ground equipment, and using these mounts with old antennas.
Ideally, you'd run a 6 gauge or larger copper conductor from the antenna mount straight down to at least one ground rod directly below the antenna. Per NEC, you need to bond that ground rod to the ground rod for your home.
You also want to ground the coax outer shield and install a lightning protection device like a PolyPhaser before the coax enters the home. Grounding the support mast would be a good idea, too.

The number of ground rods you need depends on soil conductivity. One 8 foot rod would be a good place to start, more might be needed, but that's getting outside the hobby realm.
 

budevans

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#13
What about doing a magmount antenna outside? I won't keep very high up, but how to know what size ground plane? I also have an old NMO trunk lip mount that can use. Height shouldn't be an issue, since the local repeaters are 10-15 miles away.
 
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#14
You'd still want proper grounding, but that's up to you.

A mag mount or trunk lip mount will work. You need 1/4 wavelength around the mounting point at your lowest operating frequency.
At VHF, you'd need 18 inches, or, 36 inches across. If you are only running UHF, then you need 6 inches, or 12 inches across.
 
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#15
A magmount on top of a tall metal filing cabinet or on a cookie sheet up as high as you can get it by your operating position may be sufficient if the repeaters you're interested in are only 10-15 miles away and they're at a decent height themselves.

Give it a try.

John
Peoria, AZ
 
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#17
Depends on a lot of factors.

If you want the antenna to be vertical, which is really needs to be, then the ground plane is going to be running in a less than ideal direction. You want the ground plane under the antenna, like it would be mounted on a car.

If you mount the antenna on the top edge of the window frame, you might have issues with the building materials behind the wall. Often the insulation will have a foil backed vapor barrier that will block reception. Stucco homes will have a metal lath behind it that can create the same issues.

You can certainly mount it however you want, but outside, up high and with a good ground plane are important factors. Take any of those away and performance will suffer.
 
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#18
Read 'The Bible"

Nothing is too small for grounding, until you have a problem.

Mother's R-56 antenna manual answers the simple question. There are only two hundred or so detailed technical pages on the subject.

In summary:

1. Bond -everything- together with the biggest wire possible, avoiding bends. Lightning is lazy and will only turn if it has no other choice. The ground wire is a suggestion for lightning, not a rule. Lightning already traveled thousands of feet through the air, so jumping another five feet to the air conditioner is easier than following a sharply bent wire.

2. Bond at least one 8' ground rod to the antenna system via #6 (#4 is better) and to your building electrical ground. More ground rods ten feet apart are better. Bare wire buried is also a grounding surface.

3. If possible, ground all coax at the top, every 50' coming down the tower, and always before making the turn into a building.

4. Install lightning arrestors on all coax and bond them to your grounding system.

5. If in doubt, re-read items 1 through 4.

If you think you have a failed ground, call your local rock quarry and find out who does their annual MSHA testing. That electrician has the special tools to check your grounds. Most radio guys don't.


Personally, I have three ten foot ground rods buried in my yard in a fifteen foot triangle connected by bare #2 copper and exothermic welds. One #4 connects to my radio equipment ground bar, one #4 to my 30' tower next to the house, and another #4 to my electrical entrance. Most of the copper was bought by the pound from a recycler, The insulation had been removed, and that was perfect for my needs. It wasn't bright and shiny, but after a week in the ground would't be anyway.

Overkill, but a couple years ago, my utility power drop neutral failed on the pole end. The voltage imbalance would normally be fatal to refrigerators and TV's, but because of my 'overkill' bonded grounding system the only way I knew of the failure was the sagging power line. The amperage flowing into the ground would have melted a #10 wire connecting my radio ground system to the house utility ground. That's why the NFPA code is so strict.

Another grounding story: a new government client said they were having lightning problems at their office. Before I could go out on an inspection another lightning strike traveled down the tower, jumped to the electrical system, blew up the Sheriff's microwave, and jumped between four metal filing cabinets before finding the main (copper) water line. I will summarize the secretary's description as impressive, thereafter necessitating a trip to the ladies room.

The 199' tower was ten years old, and the installer (long out of business) had grounded it with a single #6 wire on one leg. Tugging on the wire confirmed my suspicions: it was two feet long and went nowhere. Since the whole area had been recently paved in concrete, the only solution was drilling a 40' copper pipe into the ground and bonding/grounding everything to R-56 specs. A qualified electrician corrected the local building maintenance staff's 'repairs'. That was seven years ago and the tower still gets hit once a year. The Sheriff reports that his seven year old microwave is still working.
 
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