Replies

1. 
   DanH | Jan 05, 2009 08:01pm | #1

   First and foremost the antenna mast must be grounded. I'm not sure what the code details are, but electrically the shortest path to a good solid ground rod is to be desired.

   Beyond that, the coax should run through a ground block near where it enters the structure. And to protect your equipment it's best to then run the coax through a surge protector.

   The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
2. 
   BillHartmann | Jan 05, 2009 08:06pm | #2

   "810.20 Antenna Discharge Units — Receiving Stations
   (A) Where Required Each conductor of a lead-in from an outdoor antenna shall be
   provided with a listed antenna discharge unit.
   Exception: Where the lead-in conductors are enclosed in a continuous metallic shield
   that either is permanently and effectively grounded or is protected by an antenna
   discharge unit.
   (B) Location Antenna discharge units shall be located outside the building or inside the
   building between the point of entrance of the lead-in and the radio set or transformers and
   as near as practicable to the entrance of the conductors to the building. The antenna
   discharge unit shall not be located near combustible material or in a hazardous
   (classified) location as defined in Article 500.
   An antenna discharge unit (lightning arrester) is not required if the lead-in conductors
   are enclosed in a continuous metal shield, such as rigid or intermediate metal conduit,
   electrical metallic tubing, or any metal raceway or metal-shielded cable that is
   effectively grounded. A lightning discharge will take the path of lower impedance and
   jump from the lead-in conductors to the metal raceway or shield rather than take the
   path through the antenna coil of the receiver.
   (C) Grounding The antenna discharge unit shall be grounded in accordance with 810.21.
   810.21 Grounding Conductors — Receiving Stations
   Grounding conductors shall comply with 810.21(A) through 810.21(K).
   (A) Material The grounding conductor shall be of copper, aluminum, copper-clad steel,
   bronze, or similar corrosion-resistant material. Aluminum or copper-clad aluminum
   grounding conductors shall not be used where in direct contact with masonry or the earth
   or where subject to corrosive conditions. Where used outside, aluminum or copper-clad
   aluminum shall not be installed within 450 mm (18 in.) of the earth.
   (B) Insulation Insulation on grounding conductors shall not be required.
   (C) Supports The grounding conductors shall be securely fastened in place and shall be
   permitted to be directly attached to the surface wired over without the use of insulating
   supports.
   Exception: Where proper support cannot be provided, the size of the grounding
   conductors shall be increased proportionately.
   (D) Mechanical Protection The grounding conductor shall be protected where exposed
   to physical damage, or the size of the grounding conductors shall be increased
   proportionately to compensate for the lack of protection. Where the grounding conductor
   is run in a metal raceway, both ends of the raceway shall be bonded to the grounding
   conductor or to the same terminal or electrode to which the grounding conductor is
   connected.
   If metal enclosures such as steel conduit are used to enclose the grounding conductor,
   bonding must be provided at both ends to ensure an adequate low-impedance current
   path.
   (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.
   (F) Electrode The grounding conductor shall be connected as follows:
   See the commentary following 250.52(A)(1).
   (1) To the nearest accessible location on the following:
   a. The building or structure grounding electrode system as covered in 250.50
   b. The grounded interior metal water piping systems, within 1.52 m (5 ft) from
   its point of entrance to the building, as covered in 250.52
   c. The power service accessible means external to the building, as covered in
   250.94
   d. The metallic power service raceway
   e. The service equipment enclosure, or
   f. The grounding electrode conductor or the grounding electrode conductor
   metal enclosures; or
   (2) If the building or structure served has no grounding means, as described in
   810.21(F)(1), to any one of the individual electrodes described in 250.52; or
   (3) If the building or structure served has no grounding means, as described in
   810.21(F)(1) or (F)(2), to an effectively grounded metal structure or to any of the
   individual electrodes described in 250.52
   (G) Inside or Outside Building The grounding conductor shall be permitted to be run
   either inside or outside the building.
   (H) Size The grounding conductor shall not be smaller than 10 AWG copper, 8 AWG
   aluminum, or 17 AWG copper-clad steel or bronze.
   (I) Common Ground A single grounding conductor shall be permitted for both
   protective and operating purposes.
   (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.
   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.
   (K) Electrode Connection Connections to grounding electrodes shall comply with
   250.70.
   This section is new in the 2005 Code. This requirement is similar to the requirements
   for grounding electrode conductors in Articles 800, 820, and 830."

   Bascially #10 copper and connect it to the grounding electrode system.

   If you have not see it this website gives you info on size and aimming f the antenna.

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

   .
   William the Geezer, the sequel to Billy the Kid - Shoe
1. 
   wallyo | Jan 05, 2009 08:43pm | #3

   Bill if I am reading correctly #10 bare copper ran in the straightest path to the house's electrical system's grounding rod and clamped to it and a clamp at the antenna mast.This can be ran inside the attic space and down the garage wall?Do I need also to attach a grounding block to the coax, or is grounding the mast enough, and if I use a grounding block on the coax does that get tied to the antenna mast ground or is a second ground wire needed?Yes I used antenna web good site, that is where I thought I needed a larger antenna. Turns out when I moved the antenna from attic to roof I never rescanned for the stations so when told I was not receiving 7.1 by the receiver, I thought the antenna system was at fault. The problem was without rescanning the TV did not know what band width 7.1 was at. (as well as a bunch of other stations).May still go with a larger antenna because I am barely in the green according to the built in meter. Tried two in line amps they made little difference.Thanks Wally o

1. 
   DanH | Jan 05, 2009 08:52pm | #4

   If you don't have an antenna preamp you should get one. Beyond that, other amps should only be needed if you split the signal several ways.On most digital decoders there are ways to add new stations without rescanning everything.
   The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel

1. 
   wallyo | Jan 05, 2009 09:02pm | #5

   Over the weekend I brought 2; a Radio Shack 10 db and a Philps 18 db they boost the signal a bit but not a whole lot. But here is the question where is the best placement for one.? Closest to the antenna or equipment? Instructions on either don't say.Wallyo

1. 
   DanH | Jan 05, 2009 09:02pm | #7

   Like I said, a "preamp" -- an amplifier that goes right on the antenna.
   The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel

2. 
   wallyo | Jan 05, 2009 09:09pm | #9

   Got it now thanks for clearing that up.Wallyo

2. 
   BillHartmann | Jan 05, 2009 09:02pm | #6

   "in the straightest path to the house's electrical system's grounding rod and clamped to it and a clamp at the antenna mast."Yes or other point on the grounding electrode system such as the service entrance or grounding connection to the water supply.The grounding block (arrestor) can be connected to the same ground as the antenna mask or a separate wire run to the same ground electrode system.It is best place either immediately before or after the cable enters the building..
   William the Geezer, the sequel to Billy the Kid - Shoe

1. 
   wallyo | Jan 05, 2009 09:06pm | #8

   Thanks again Bill as always you are a breath of fresh air! Now to find a good deal on 40' of bare #10.Wallyo

2. 
   DanH | Jan 05, 2009 09:13pm | #10

   It should be noted that the grounding block isn't technically an "arrester", since it contains no spark gap or MOV to shunt the center conductor to ground in the event of a surge. There are true stand-alone coax arresters, but they're fairly scarce, so it's advisable to route the cable from the grounding block into a surge-suppressor plugstrip which includes a coax suppressor (after first going through the preamp power supply, if there is one).Antenna => Preamp => Downlead => Grounding block => Preamp power supply => Surge suppressor => Splitter or splitter/amp => TV
   The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel

3. 
   gfretwell | Jan 05, 2009 09:58pm | #11

   I would drive a rod directly under the antenna mast and bond to that, keeping the grounding conductor as straight and short as possible. Then you bond that electrode back to the service electrode system to reduce ground shift.