Ground the Antenna Mast - lightening protection?

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Kenneth G. Feldman:
Hi,
    I put up an antenna mast that extends about 10 foot above my roof line.   I use the mast to support an inverted V dipole.  I disconnect the coax from the radio and ground both inner conductor and shield when not in use.  

     The antenna mast is not currently grounded as the base is on a lower roof.  The mast does not extend all the way to the ground.    I looked at some houses in the neighborhood that have a TV antenna mounted the same way.  The antenna masts are not grounded.  

     There are trees and power lines that are higher than the mast within 100 feet of the mast.  There are lots of taller structures (High voltage transmission lines, water towers, cell towners) within a mile of my house.  I.e better targets for lightening.

    I checked the ARRL Antenna Book and it basically says to tie the antenna into the existing lightening protection on a building.   None of the houses in the neighborhood have any lightening rods.  

    I plan to install a gas discharge surge protector on the coax just before it comes into the house.  **** Should I ground the Antenna Mast? **** If so, I'm guessing I should use the heaviest gauge stranded wire I can get.  

    Thanks.

KB3MDT

Michael S. Higgins:
By all means ground the bottom of the mast to a ground rod. At the same time the antenna feed should be run through a lightning protector and tied to the same ground. In addition the ground from the antenna mast must be bounded to the electrical ground at the AC panel.

Wither your coax is connected to a radio or not it will still conduct a lightning discharge into your home. All grounds must be tied (bonded) together. Also put surge protectors on your AC panel for 90% of lightning damage to homes come in the AC feed from the power poles.

Steve Jackson:
Two answers:

1.  Yes, you should connect your mast to earth via the heaviest gauge wire you can install, and to the biggest ground rod you can have, hopefully at the utility service entrance where the home's existing ground rod is ... becuae you need to bond them together at that point.

2.  Don't bother with any of that.  You're no more apt to get hit by lightning with or without the little roof mast you have, just like your neighbors haven't been hit, either.  People make WAAY too big a deal about grounding small masts and such, lightning is BIG and SCARY ... hoo boy.

Why I Have Two Answers:

Because I do both.  

On my house I have a 10 foot or so mast, like yours, ungrounded.  BFD.  This weenie little mast is no more of a lightning attractor than my you-know-what.  if ligthning is going to strike my house it won't hit ONLY the small mast, and it won't be BECAUSE of the mast, either.

Also, about 300 feet back ikn the woods, I have an 80 foot tall Rohn 55G tower with 16 feet of rotating mast above it, holding what looks like a huge cloud of aluminum!   I have a ground system out there that makes most broadcast stations' ground systems look like crap.

Oh, I know what could get hit, and here in NC, we get HIT by summer storms!  Funny, though, in all these years I have yet to take a strike.  Know why?  Maybe because the tower is SO well grounded that a charge never has the chance to build up!  But if one did, I'm not sure I'd even notice it.  My radios are always connected and always on, 24x7.

Ultimately, only *you* can judge what level of safety versus unwarranted paranoia you can balance.  All I can say is, TV and radio stations and cellular and two-way towers don't disconnect when there's a thunderstorm, and neither should you have to, if you do it right.

Jon M. Pollock:

Hi,

You are taking a BIG risk if you don't make a serious effort to make a good lightning protection ground for that mast.

Lightning is VERY unpredictable... just because there are "other" objects in the area is NO guarantee of any kind that you won't get hit.

Coax is NOT adequate for grounding protection...you need a rock bottom minimum of AWG # 4 wire if your want REAL protection. Also, one 8' ground rod is also a bare minimum...put in TWO rods, atleast 8 to 15 ft. appart.

FYI. Inadequate or improper grounding of your ham radio antenna could give your insurance company an excuse NOT to pay a claim...and that is expensive.

Think about this: A lightning bolt, particularly a big one, contains several MILLION WATTS of energy that must be dissapated in a less than a second... if you don't give it a good low resistance path to ground, WHERE DO YOU THINK THAT ENERGY WILL GO??  (Answer: into your house wiring, pipes, telephone line, cable TV, etc. etc....because it WILL find ground!)

Bottomline: how much are you willing to bet you will NEVER get hit??  (because you ARE betting REAL money!!)

73,  K0ZN

Alan Applegate:
Mr. Jackson, I'm surprised you didn't mention the "Cone of Effectiveness" area offered by your 80 foot tower. I am aware you don't see much about this in print, but nonetheless what data there is suggests it is a real benefit. Obviously, it requires a good installation which yours appears to be.

Alan, KØBG
www.k0bg.com

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