Lightning Loops?

[w5rkl]

Power for the shack is 240VAC from the house panel.

The house panel has all house wall outlet safety grounds and WHITE neutral wires connected together on the house panels' neutral buss bar.
The house ground rod is also connected to the house panels' neutral buss bar.

Power to the shack is 240VAC over 8-3/G wire, taken from the house panels' main power buss through a dual breaker. The 8-3/G RED and BLACK
wires connect to the house main power buss and the "WHITE" and #10 solid copper wire connect to the house panels' Neutral buss bar.

The other end of the 8-3/G wires connects to the shack panel, RED and BLACK to the shack panels' power buss, the WHITE wire and
the #10 solid copper wire connect to the shack panels' Neutral buss.

Each 120VAC outlet in the shack, there are 5, and the single 240VAC outlet, have the safety ground and Neutral wires connected together
on the shack panels' Neutral buss bar.

I questioned the electrician if connecting the safety ground and White neutral wires together in the shack panels' Neutral buss bar was
according to code and he said yes. I thought the shack wiring was considered a "sub paneL" but he said no. The only thing he said I
didn't need was the ground rod outside the shack that connects to the shack panel Neutral buss bar. He said the house already has a
ground rod so an additional ground rod was not needed at the shack. I insisted on the ground rod so he installed it and connected it to
the shack panels' neutral buss bar.

As I said, I'm not an electrician and that's why I hired a licensed electrician to do this job. I don't want something major to happen because of a
wiring error.

73s
Mike
W5RKL

[K5UJ]

Hi Bill, thanks--yes I hasten to add they take a lot of hits or nearby hits with little or no damage and that incident I was thinking of was unusually bad. 

rob

[W4NEQ]

In my experience it is a rare "licensed electrician" who understands effective lightning protection.

The main principle is providing a more attractive (low impedance) alternate path for the stroke current to flow to ground.  NOT flowing through expensive equipment or your electrical system.  AM stations have exceptionally low impedance ground connections due to all of the radial wire surface area in contact with soil spread over a wide area.

[k4kyv]

I'm not sure that's a good idea. I believe there should be one and only one point in the entire system where ground and neutral are connected together, and that's at the entrance to the main panel, right at the meter.

That is required by the NEC.

Bill

I looked it up in several NEC "Handbooks" in my library, and a copy of the early 1980s NEC.  I could find literally pages devoted to grounding, but the only thing I could find on that specific topic was in the earliest (1940) edition.  It says that the neutral in a separate building that is part of a single system may be grounded, but didn't imply that it was required. They mentioned that this situation is found most often in farm buildings that operate off the main house's electrical system, but that's not too different from a separate ham shack.

The NEC is like attempting to decipher the schematic of a ricebox. They have topics and sub-topics detailed in minutia, but if it is in any logical order, I haven't figured it out, and the index in the back of the book is about as useful as the search function on this BB.

But still, I can't figure out why a separate building would be treated any differently from a room added on to the main house, since it would make zero difference electrically.  In the latter case, it is a strict no-no to ground the neutral anywhere else but at the one point at the main panel entrance.

Codes notwithstanding, I'll still use whatever results in the least RFI and hum in the audio equipment.  If they changed the code since my book was published, I'm still covered, since my ham shack was built in about 1930 and pre-dates my 1940 book, so any existing electrical wiring would be grandfathered. And to boot, despite some extremely close if not  direct lightning hits, I have had relatively little lightning damage, and I don't even use any lightning loops.

[W4NEQ]

Don,

I'm not surprised you don't have many lightning problems.  I recall seeing signs of arc-overs on your tower spark-gap.  And how many feet of buried copper wire do you have in the ground ... ?

Chris

[KA3EKH]

Good conductive paths to ground are great if you're buying into the elevated theory; don’t help much with the EMP thing and the Stati Cat people will tell you all about how their product prevents strike in the first place. Thousand points of discharge or light or something like that. More than likely jinx myself by saying this but at the several broadcast sites I have had little or no damage by lightning to the RF equipment, tons of damage to telephone stuff. But other times have had strange things like last year had a lightning strike burn a small hole thru the copper alloy body of a multibay antenna and not affect the antenna or on air operations, just lost pressure on the antenna and line and that’s how we discovered the problem. Lightning dose weird things, just yesterday we had a storm in town and less than a quarter mile away from the five hundred foot very well grounded Stainless G7 tower for WCPB-TV the lightning avoided that structure and struck instead the steeple of an old church in town and blew half the shingles from that structure. Don’t know if they had a lightning rod or not but it did blow the hell out of that church. Go figure.

[W4NEQ]

The "elevated theory" is the basis for the single-point ground attachment method - always a good idea but not always practical.

Most AM tower spark-gap arc-overs are due to the "emp" induced energy from a nearby strike and not direct hits, but as heights get taller direct hits become more frequent.

Hate to endorse any particular product, but with the advent of the "Optelator" damage via dial-up phone line connections are pretty much a thing of the past.  The product optically couples tx & rx via four inches of fiber, entirely without metallic connection.  It does reduce the level a bit however.

Tower mounted antennas are most vulnerable when at or close to the top.  As painful as it is to give up height already purchased in steel, side-mounted FM antennas do much better with lightning when the top bay is at least ten feet below the top. 

Chris

[k4kyv]

Why not just add relatively cheap tubular mast to the top of the tower, to extend above the FM antenna?  That should be sufficient for lightning protection and you wouldn't have to mount anything on it.

[w5rkl]

I live on a corner and there is a power substation at the corner. The substation is about 500 feet from the house. The substation receive power
from a 60KV line that hangs from 2 200 foot tall metal poles, one of which is about 250 feet or so from the house. I had the electric company
out tracking down a noise source, turned out to be a blown lightning arrestor in the substation. The lineman said I'm protected from a strike
by the metal pole that's closest to the house. Both poles get hit quite a bit during the 8 years I have lived here. My neighbors' house is
about an additional 200 feet farther away from the pole, had a 60 foot pine tree received a direct hit. The pine tree was 10 feet from his house.
I'm not sure if the 60KV pole actually provides any protection or not. I can only say, knock on wood, we have not been hit during the 8 years
we have lived here and I hope we don't get hit in the future. The substation also has a tall wooden telephone pole with a 6 foot tall metal
rod on top with a large diameter, possibly #4 copper wire, running down the pole to a ground rod. This pole is situated in the middle of the
substation.

73s
Mike
W5RKL

[W4NEQ]

That is also done, often with multiple-point "spike-ball" style lightning rods / "static dis-chargers".

I forget exactly what the legal limits are regarding height extensions above the top beacon, and where they have to be declared.  20 feet comes to mind but I can't remember if that counts toward busting the limits of the lighting requirement for the height - for instance lots of 499 foot towers built to avoid the more stringent lighting requirements for 500 and above.  But these rules have changed in recent years with strobes ...

[KA3EKH]

That site that had the hole burnt into the antenna is WQHQ; a class B (50kW ERP) FM that has an eight bay Dielectric antenna that has its top bay located just about five feet below the top of the tower with the entire antenna assembly being about sixty feet long. On that tower there is a lightning rod that extends above the top beacon but in this case the lightning decided not to strike that but instead hit the outside tip of the center support pipe on the bay and burnt a hole about a 1/8 inch clean thru the stainless steel pipe. Couple pictures of what the bay looks like and the tower rigger who had to climb up six hundred and fifty feet to replace it. Like I said before had no idea what happened because everything was on air and normal except we lost pressure on the line and antenna and received telemetry about that. The antenna, bays and transmission line are all hallow and we keep a nitrogen charge on them and if the lines drops pressure that generates a fault in the remote system and calls you. I was also involved with the replacement of a four bay ERI FM antenna for WSCL this spring. That antenna developed a problem in the tuning slugs and started to burn there and proceeded to burn up most of the hardware above the network and the inter bay connectors. The soot and fire damage resulted in having to replace the entire antenna for around $30,000.00 not including installation. The popular speculation is that this was also caused by lightning although all the damage started around the stub section at the base of the antenna and the antenna is side mounted at five hundred feet fifty or sixty feet below a forty foot high television antenna. So when it comes to lighting, where, when and what it's going to do all bets are off. In regards to the phone stuff, I have seen the optical things before and thought they looked like they would work good, may have to think about getting a couple for the more problematic sites. The thing I do most often is just load up on these little cheap phone line protectors that plug into a wall outlet and the phone line loops thru them. They have fusses and other junk in them that blows out but generally the equipment is protected downstream of them so after a storm will often end up going around to sites and replacing the blown ones but that also provides job security. Here's a question, at the WJDY AM site I have a two tower 1.470 5.0 kW station that has the transmitter building located two hundred feet from each tower. The ATU at the base of each tower are connected back to the transmitter building by 7/8" healiax cable and each tower is around 180 feet tall. Each tower has a ground matt and around a hundred radials that have all been installed back about forty years ago.  This site has the most problems with phone lines. Program audio is provided by a STL to the site so that’s not an issue but the remote control for the transmitter constantly is having issues. Almost every storm the phone coupler gets wacked, have on occasion had things like the telephone block outside distroyed and once or twice seen the service loop from the phone company blown apart. Remember that the transmitter building is at least two hundred feet from the towers and the equipment, except the remote never have any issues so why does the phone line keep exploding? My best speculation at this point is that the grounding system looks so good to the phone line that any strike on the phone line around the site and the potential wants to travel here to dissipate? But that's just a guess; twenty years ago I would have explained it all, now I just don’t know. It may not have a lot to do with AM but lightning is a fascinating subject and seeing what it's done is always fun to talk about.

[RolandSWL]

 Thank you all for the information. Is there any virtue in using AlphaDelta ATT3 G50 Static Discharge Protectors?
 If so, would I need one for each antenna? I am contemplating a variety of wire antennas, each of which will feed into a remote coax switch.

Roland........
 

[Steve - K4HX]

The in line static protectors can't hurt. If you are using tube receivers, you probably won't need them. Also be sure the static protector can handle RF if you are going to transmit.


In general, lots of good grounding and bonding info in doc like this.

http://www.qwest.com/techpub/77355/77355.pdf

[Bill, KD0HG]

Those poor tower guys are often making less than $15/hr.
To swap out light bulbs, sometimes.

For one of the toughest, ballsiest jobs on the planet.

God Bless them.

Bill

[k4kyv]

That's what the guys who do the actual work get paid. But the station usually pays a sub-contractor a lot more per climber even when it's a one-person job.  Can't understand why a professional tower climber wouldn't contract his work independently and keep everything for himself.  

Back in 1964 I climbed a 365' tower and replaced all the bulbs, for $30.  Seemed like big money back then.  A couple of years ago I was offered a retired BC1-F by a small station in exchange for replacing the lights on a 250' tower, but I had a physical infirmity at the time and couldn't do the work (since then fully recovered), plus moving the double-wide 3000 lb. transmitter and hauling it 100 miles.

I'm not afraid of heights as long as I have full confidence in the integrity of the structure I'm climbing on. But when I built my tower, I had to temporarily guy each section on the way up.  I couldn't relax working more than one tower section beyond the top set of guys and feeling the tower sway with my movements.

But once you get up beyond about 40 ft, it doesn't really make any difference, if you have the physical stamina for the climb.  You will be precisely as dead falling from a 40-footer as from a 400 footer.  Last year, at Field Day if I recall, there were a  couple of separate incidents where someone was killed when a tower or mast about 30 ft. high collapsed while they were on it.

[RolandSWL]

Hi All,
 
 Thanks for all the great information. I am going to run my coax and control cable (for the remote coax switch) through schedule 40 plastic conduit.
 I thought since the pipe is going to the back of a storage shed, why not run a length of Romex as well as the shed is as yet, un-electrified.
 Would the Romex cause any problems when I eventually get my Ham ticket and start transmitting?

Thanks, Roland......

[WBear2GCR]

We discussed this in a previous thread:

I like the case where there is galvanic isolation between the main service and the remote service.
Don't recall the NEC term for this, but it exists. That way you can put your "ground" locally to the remote service, which would be the shack. (assuming a separate building)

I don't know but would presume that some method to handle a bleed of extreme over voltage from one side of the iso tranny ground to the other (like a spark gap or maybe a big ass MOV or Tranzorb) might also make sense.

It is studied and accepted practice that the self inductance of a large iso tranny will be a very effective transient killer, equal or better than more complicated active or passive methods - just bigger and heavier.

In a "regular" set up, where you have to run a long amount of copper back to the service, to me it looks like the self inductance of the wire and the vdrop could cause one side to be one heck of a lot higher than the other...  but obviously if everything rises *nicely* together, no damage; I'm not so sure that this will happen unless all the conductors have the same drop... so using a fat gauge for the "ground" run and a standard gauge for the others will create a differential voltage. Or so it seems to me.

In the case where you still bond back to the service entrance with a long run, it seems that maybe having the iso tranny in the other lines might be of some benefit, as those lines more or less float.

Those outside things like connections to twisted pair or cable definitely can cause a voltage difference, and blow up solid state things. It's easier than before to go wifi and get rid of those connections...

Oh, people have suggested using stainless steel chimney brushes up top on the tower... seems like it should work ok.

                   _-_-bear

[WA1GFZ]

I have a friend who had a problem with his computer controlled wave solder machine.
Software would get trashed whenever a storm came through. He added an isolation transformer that did nothing. Then he called me. I suggested he establish a ground after the transformer. He drove a rod into the floor beside the machine and never had another problem.

[WBear2GCR]

So... the ground with the transformer? Or just the ground?

                    _-_-bear

[Bill, KD0HG]

That's what the guys who do the actual work get paid. But the station usually pays a sub-contractor a lot more per climber even when it's a one-person job.  Can't understand why a professional tower climber wouldn't contract his work independently and keep everything for himself. 

A lot of that cost is insurance- workers comp payments. Tower work is a hazardous occupation per man-hour and the cost of insurance is insane. Have an accident or a claim and the cost gets even more insane. There has been some online news about tower accidents the cell phone companies have had. Reports of too much rushing on the jobs.

Bill

[WA1GFZ]

In addition to adding the transformer.

A thunder head formed over the beach last night as I watched from inside the  house. I watched it grow taller and taller and wondered if it would turn into a tornado. It produced one good bolt close by. The 200 foot inverted U above the yard produced a good long duration arc against the ground. I wonder if it hit Joe PJP across the pond as it drifted south.

[Bill, KD0HG]

OK, here's a classic.

Last Saturday afternoon a big time strike hit one of the 350' towers of a Denver 50KW AM directional.

The tower and tuning building were grounded as best as humanly possible with perimeter ground straps 4 and 6" wide and the customary 180+ quarter wave buried radials. Far better than 99.99% of ham installations. It was only a few months ago when I had inspected the ground system. There was a multiturn loop of 3/4" copper between the tower and tuning house.

Well, last Saturday, a strike completely torched the tuning house. An aluminum and wood 10x10 foot prefab building. The tower matching network was in a solid steel enclosure containing the inductors and caps inside the building.

All burned to the ground. Austin tower light transformer? Melted. All torched. The copper inductors in the picture were once enclosed inside a stout steel enclosure, which was vaporized. The 3" buried Heliax feeding the tower? Vaporized back some 10 feet. Prolly a 100K worth of total damage.

Nature wins, again.

Now, what did I say about lightning protection?



Bill

[W4NEQ]

Shoulda had your gap tighter ...

In all seriousness, what investments do you like?  (I'll mark those off my list!)

[Bill, KD0HG]

well, I have some sort of employment security for the rest of summer- LOL Need to get the loader and backhoe out there.

[KA3EKH]

CC 50 kW AM stations are all monsters, I have never worked at one myself but I do have a couple 5 kW and have worked on many other 1 and 5 kW properties. Is it possible that what you are looking at is the result of the lightning strike causing damage to the ATU at the base of the tower and when the transmitter recycled the damaged ATU set itself on fire? I had an old style CP current meter in line in a steel Gates Radio cabinet with the phasing network fail once and the 5 kW transmitter acted like a plasma torch gone wild, first it burnt and destroyed the meter and then it arced from where the meter had been and burnt away at least three or four inches of steel from the cabinet.  When I got the call that it was off the air when I got to the site I started the transmitter and saw the purplish pink flame start burning the cabinet again. Funny thing is that while this was happening the transmitter did not go into VSWR fault. If a 5 kW can do this much damage and burn things like a Bakelite meter and steel plates a 50 kW can do way more damage and easily burn up a ATU building, I can kind see lightning starting a problem but have to wonder if you’re looking at damage that occurred because of the lightning but was also result of the output of the transmitter? Also do you ever do base current readings, not via Delta loop but with a real thermocouple meter? The couple people I know who work with the 50 kW stations always describe doing the base readings as an experience.