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Old 11-27-2007, 05:48 PM   #1
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Grounding Antenna


I purchased an HDTV, and with my rabbit ears antenna got 15 new air broadcast high def stations. I'm now going to install an on the roof antenna.

Codes require the antenna to be grounded to a grounding rod placed below using #8 or #10, as lighting does not take corners particularly well only a grounding rod below will do pipe is not acceptable. They then want #6 going from my grounding rod from the antenna to the breaker panel on the other side of my house.

What's the purpose of connecting the grounding rod from my antenna to the breaker panel on the other side of my house which already has 2 grounding rods?


Last edited by Piedmont; 11-27-2007 at 05:51 PM.
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Old 11-27-2007, 06:19 PM   #2
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Seems very odd. All I can think of is due to the antenna lead coming into the house. I have an HDTV antenna in my atic and it works great ... no need for ground.

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Old 11-27-2007, 07:28 PM   #3
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So if you are bonding the antenna ground to the service ground, why not just run #6 to the service ground? That is effectively what they are trying to do right?
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Old 11-27-2007, 07:51 PM   #4
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ARTICLE 810 Radio and Television Equipment
I. General
810.1 Scope

This article covers antenna systems for radio and television receiving equipment, amateur radio transmitting and receiving equipment, and certain features of transmitter safety. This article covers antennas such as multi-element, vertical rod, and dish, and also covers the wiring and cabling that connects them to equipment. This article does not cover equipment and antennas used for coupling carrier current to power line conductors.


810.21 Grounding Conductors — Receiving Stations

Grounding conductors shall comply with 810.21(A) through 810.21(K).


(E) Run in Straight Line
The grounding conductor for an antenna mast or antenna discharge unit shall be run in as straight a line as practicable from the mast or discharge unit to the grounding electrode.

(J) Bonding of Electrodes A bonding jumper not smaller than 6 AWG copper or equivalent shall be connected between the radio and television equipment grounding electrode and the power grounding electrode system at the building or structure served where separate electrodes are used.


Commentary following (J):

The requirements for grounding are in accordance with Article 250. Antenna masts must be grounded to the same grounding electrode used for the building's electrical system, to ensure that all exposed, non–current-carrying metal parts are at the same potential. In many cases, masts are connected incorrectly to conveniently located vent pipes, metal gutters, or downspouts. Such a connection could create potential differences between lead-in conductors and various metal parts located in or on buildings, resulting in possible shock and fire hazards. An underground gas piping system is not permitted to be used as a grounding electrode.
Section 810.21(J) clarifies that the bonding requirement applies only to electrodes at the same building or structure. The use of separate radio/television grounding electrodes is not required.
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Old 11-27-2007, 09:35 PM   #5
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Right you are Speedy. I missed the seperate electrode.
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Old 11-27-2007, 10:15 PM   #6
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Depending on your location with respect to the TV towers, an "on roof" antenna may not offer any improvement over rabbit ears. There is no such thing as a HDTV antenna, the ads are just hype. Any antenna will pick up both analog and digital signals. The key specs in looking for a TV antenna are directivity, gain, and F/B ratio. That applies to either analog or digital (HDTV).

I had an "on roof" antenna that was grounded per code that Speedy posted. I had disconnected the antenna because it didn't offer any improvement in TV signal over rabbit ears. I just never got around to taking it down. It was hit by lightning about 10 years ago. It didn't take a direct hit, a nearby cottonwood tree took the direct hit. I still find pieces of the antenna in the yard to this day.
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Old 11-28-2007, 04:35 PM   #7
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http://etdxa.org/05_Article_810_Download%202.pdf


Try reading this....
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Old 11-28-2007, 05:43 PM   #8
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Chris, that is a great presentation by Mike Holt. I've never seen that before.

Thanks!
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Old 11-28-2007, 06:35 PM   #9
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Quote:
Originally Posted by Speedy Petey View Post
Chris, that is a great presentation by Mike Holt. I've never seen that before.

Thanks!
I'll try and dig up some other links I have...

Check these out, they are all very good...

Article 680

Top 101 Rules of The NEC, parts 1-4

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Old 11-28-2007, 09:08 PM   #10
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bump...
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Old 11-28-2007, 09:09 PM   #11
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I have the 680 one but it's good you posted it for everyone else to see.
The Top 101 one looks cool as well.
Thanks again.
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Old 11-29-2007, 11:28 AM   #12
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Wow, that is a great link and thanks all for the reply. I didn't know you couldn't attach 2 wires to the grounding rod with 1 clamp. I'll have to pick up another clamp. It makes sense about trying to keep all the levels the same by bonding the grounds together... though I don't know why 6 awg that's thick cable!

If anyone's thinking about getting an antenna cause in Feb 2009 all TV analog signals will go dark here's what I found. 1st as mentioned there is no such thing as a digital antenna they wanted to make sure that no one had to replace their current. Originally they thought VHF signals would be eliminated, hence UHF only antennas but they decided to keep it so you're best getting a VHF/UHF one. Digital signals are going to be broadcast at less signal strength, Channels 2-6 will reduce from 100kw to 50kw. Channels 7-13 from 316kw to 160kw, and channels 14-69 from 5 megawatts to 1 megawatt. You'll need a bigger antenna to compensate for weaker signals, or may lose stations when the switch happens. Many of the broadcasting towers are directional (usually directing their signals towards major cities) even if you live close to a tower you may not be able to get that station if it points away from you towards a major city. Likewise being on the opposite side of a major city in the broadcast path you may be able to pick up signals from large distances. Trees are very good at blocking signals, in winter without leaves you get more/better stations. Because of overlapping frequencies, changing the height of an antenna a foot or two can make a huge difference on improving/worsening reception or may give you a station you never had before or cause you to lose one you had.

Rabbit ears are good if the towers are within 5-10 miles, amplified ones up to about 15. Roofs typically reflect 1/2 the signal so antenna in an attic will have half the reception of that same antenna outside (attic antennas are good for 20-30 miles) but that depends on metal and moisture content of the roof. An attic antenna under a dry asphalt roof in dry desert climate will have almost no degredation of signal. A metal roof or radiant foil barrier attached to the rafters will block 100% of the signal making an attic antenna unwise. A wet surface reflects nearly 100% of the signal so an attic antenna under a wet roof will suffer almost complete loss of signal whereas, an outside one above a wet roof will experience an increase (or experience ghosting). Lastly snow on the roof will diminish signal strength and if snow piles on your roof for extended periods of time an attic antenna is not recommended. An attic antenna does not need a ground, outside must be grounded.

I went for the biggest outside antenna that was compatible with the rotor I wanted (131" in length), the broadcast towers closest to me are 40 miles to the east (a major city), 50 miles to the north (another major city) and 60 miles to the south so that's why I needed a big antenna and rotor. 15 digital stations were found with my rabbit ears but they're not watchable (I get about 1 second of watching for every 10-15 seconds they "retrieve data") except for channel 7, which just gets blocky several times an hour I'm hoping the outside antenna is the way to get them all.

Last edited by Piedmont; 11-29-2007 at 01:04 PM.
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Old 11-29-2007, 03:34 PM   #13
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If you wanna know what antenna you need to buy visit this web site...

http://antennaweb.org/aw/welcome.aspx

I have an antenna and get ALL my locals in HD. But Directv does the same thing, but with an antenna it's all free!

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