Second grounding rod? And what coax antanna discharge unit to get? - AVS Forum
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post #1 of 7 Old 05-20-2008, 03:22 PM - Thread Starter
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Because of significant ground-level blockage/multipath of my local OTA ATSC broadcast towers (all of them UHF), I installed the Antennas Direct DB2 antenna on the top of my roof using their 18" mount. This has provided an ample and pretty clean signal for input into a splitter/amplifier in my basement.

Anyway, I need to ground this antenna installation. My problem is that for line-of-sight I had to place the antenna on the side of the house opposite of where my home ground is located. To connect the antenna to the home ground I'd have to use about 80' of wire for each ground conductor, while if I put in a new ground rod on the other side of the house I'd only have 18' to 20' per wire. (If I do the latter, what gauge/type of wire should I get? I assume it can be insulated to reduce corrosion.)

So even if not optimum, will it work for me to drive down a new grounding rod and connect to that? That is, is this better or worse than nothing? I continue to read the very strong admonition to use the house ground if at all possible, with no explanation why (go ahead and get technical!)

Another question is that my coax directly enters the attic right at the antenna base. Obviously I need to put in a coax antenna discharge unit (or whatever they are called) pretty much right at the antenna. I find very little discussion as to where to get these or what brand(s) to consider, and how much they may attenuate the signal. Recommendations here wanted.

Btw, I live in Utah with very clay-like soil, so what is recommended for a grounding rod (or whatever) should I put a second one in?

Thanks in advance!
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post #2 of 7 Old 05-20-2008, 03:41 PM
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Here is someone in favor of using a second grounding rod when necessary--http://www.hdtvprimer.com/ANTENNAS/basics.html. Nice diagrams and explanation.

Where the coax enters the house you need a grounding block. You can get them online or anywhere TV cable is sold. They look like this and are inexpensive--


There are also a variety of inline surge protection devices such as this one--http://www.citelprotection.com/citel/p8ax_details.htm

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post #3 of 7 Old 05-20-2008, 03:54 PM
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Quote:
Originally Posted by jnoring View Post

Because of significant ground-level blockage/multipath of my local OTA ATSC broadcast towers (all of them UHF), I installed the Antennas Direct DB2 antenna on the top of my roof using their 18" mount. This has provided an ample and pretty clean signal for input into a splitter/amplifier in my basement.

Anyway, I need to ground this antenna installation. My problem is that for line-of-sight I had to place the antenna on the side of the house opposite of where my home ground is located. To connect the antenna to the home ground I'd have to use about 80' of wire for each ground conductor, while if I put in a new ground rod on the other side of the house I'd only have 18' to 20' per wire. (If I do the latter, what gauge/type of wire should I get? I assume it can be insulated to reduce corrosion.)

You need to put a ground rod into the ground as directly below the antenna system as you can. An 8 foot rod with 6 AWG wire. Connect this ground rod to your house grounding system somewhere.

Quote:


So even if not optimum, will it work for me to drive down a new grounding rod and connect to that? That is, is this better or worse than nothing? I continue to read the very strong admonition to use the house ground if at all possible, with no explanation why (go ahead and get technical!)

Another question is that my coax directly enters the attic right at the antenna base. Obviously I need to put in a coax antenna discharge unit (or whatever they are called) pretty much right at the antenna. I find very little discussion as to where to get these or what brand(s) to consider, and how much they may attenuate the signal. Recommendations here wanted.

Btw, I live in Utah with very clay-like soil, so what is recommended for a grounding rod (or whatever) should I put a second one in?

Thanks in advance!

An 8 foot rod is required. The intent is have 25 ohms or less resistance to the earth, that is hard to measure and needs special equipment. If you have one rod for your house system in similar soil I would assume one would be OK for your antenna, if you have two for your house then consider two for your antenna. Do put a rod below your antenna installation, it's the safe way, and connect to your house grounding system.

The attenuation is not too much.
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post #4 of 7 Old 05-20-2008, 04:19 PM
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I don't know the specifics but your equipment will suffer if you have separate grounding rods. Connect them. I lost two C Band power supplies due to this mistake.

"The purpose of diplomacy is to prolong a crisis." Spock, Mark of Gideon, TOS
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post #5 of 7 Old 05-20-2008, 05:15 PM
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Quote:
Originally Posted by Davinleeds View Post

I don't know the specifics but your equipment will suffer if you have separate grounding rods. Connect them. I lost two C Band power supplies due to this mistake.

An antenna has to be for code and should be for safety run to a ground rod by the shortest practical path, if that goes to your house grounding rod then attach to that. If your antenna is farther away from your house ground rod then you need to add a second one.

If you have two or more ground rods they must be connected together. If you didn't connect the two rods together then that was a mistake that could take out a power supply.

Multiple ground rods, one grounding system.
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post #6 of 7 Old 06-01-2009, 11:56 AM
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Citel's P8AX Series is a ultra low capacitance gas discharge tube (GDT) based surge arrestor designed for use in high frequency RF applications up to 6.9 GHz. The P8AX protects sensitive equipment connected to a single coaxial line from a direct lightning strike. The P8AX is installed in series with the line and has several standard grounding options including a grounding screw, mounting bracket or bulkhead.

Available with the most commonly used connectors including BNC, F, N, SMA, TNC, and 7/16 Din connectors or it can be custom made for your application with any combination of connector and gender types to eliminate the need for any adapters.

The P8AX can be used in systems supplying up to +/- 48 volts DC via the coaxial cable and can be provided in 70, 500 and 1,000 watt versions for any 50 or 75 ohm network.
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post #7 of 7 Old 06-01-2009, 11:58 AM
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CITEL has moved to a new website citel.us You can download any of the data sheets there as well.
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