Lightning Arrester

[ocn29rsc]

I have never messed a lot with lightning arresters so I have a question about installation.

Where is the proper placement of an arrester? So do I put a short pig tail coming off the antenna and attach it there followed by my LMR-400 or do I put it inside my little radio room near my scanner?

I have always grounded my mast and towers just never messed with arresters much.

Thanks for the help.

J. Cody

 

[CSXRiverline]

The lightning arrestor should be placed at or near the point where the coax enters the house, so I suspect the short pigtail from the antenna to the arrestor, then to your coax is the correct method.
In addition, the arrestor must be connected to the antenna ground conductor.

When purchasing the lightning arrestor, you want one with a higher joule rating. The higher the better, as it would handle more energy before being destroyed.

An even better method of protecting your equipment would be to disconnect it from the antenna when not in use and/or when a lightning storm is threatening.

FW

 

[gewecke]

Yep! What he said. Lightning loves this hobby!

 

[CSXRiverline]

But keep in mind that it takes far less than a direct hit to kill the front-end of any radio.
During a strong TS, a lot of current can flow through the antenna, as the atmosphere itself is full of charge.
A properly grounded (per NEC) antenna system should actually reduce the chance of being hit, since it will help to discharge the atmosphere before the charge can build high enough for an arc, ie; lightning.

The Ringo Ranger ARX-2B I am in the process of putting up is a very good antenna when it comes to lightning protection.
Its matching system looks like a dead short to DC.
Still, I'm not playing games with lightning. My radio will not be connected to the antenna during storms.

The quality of your grounding system will determine how well your lightning arrester will perform.

FW

 

[OceanaRadio]

Attach your arrestor directly to a ground rod outside the point where the coax will enter the residence.

Strongly recommend that you shield-ground the coax at the first point it reached ground-level from it's mast. Connect that shield-ground to a ground rod, the same one you sunk to bond the mast itself.

Bond those ground rods with #4 solid or stranded copper wire to BOTH the rod used for the antenna-mast AND the home's AC service entrance ground rod.

Now a couple of things about other comments posted.

SInce a ligthning strike has only a small percentage of DC energy, with the majority of it's rapid-rise time in the 50-100MHz range, the "DC-Shorted Antenna" is purely a sales-gimmick that offers no protection from an attachment. Neither does any amount of grounding or masts in the air diminish the liklihood of an attachmnet to your antennas or structure. The upward-flowing streamers of positively-charged ions that emit from every corner of your roof, roof peaks, antennas, trees, and people if they happen to be in that ion-saturated environment, is what attracts a downward-flowing step-leader that was going to attach to SOMETHING in that immediate area ANYWAY, whether your house or antenna (or you) were there or not.

Unplugging equipment is something we all go through when we are getting started, and some people perform this possibly death-defying act all their lives during thunderstorms that sneak up on them. After you do that manauever long enough, have enough close-calls, or forget completely enough times to be lucky (or not), most folks realize they could protect their whole house from fire as well as protect radios from the most likely nearby strike with a little foreplanning. Serious planning can protect even from direct attachments, as we know all radio transmnission towers, cell towers, etc survive frequent strikes.

The odds of a 1-percentile lightning strike of 200-300Ka energy (which could overcome most residential-grade grounding systems) are so small that they are not factored into the design of any but very sensitive systems (fuel docks, explosives facilities, etc). Your mileage will be fine with following the NEC and NFPA 780 standard for lightning protection. After that, you'll realize the most important thing (for you) to disconnect is the AC power to the radios, because you hadn't learned yet that most damage to them comes IN the AC power lines and OUT via the antenna grounding system. Fairly expensive surge protection at the AC entrance (meter), and again in the shack is the prerequisite there.

Meanwhile your coax surge-arrestor is a good start, it is certainly better than nothing, even if you continue to unplug until the day when you may eventually have a balanced protection system in place.

R/
Jack

 

[CSXRiverline]

Good post Jack;
Do you have any recommendations for lightning/surge protectors for the feed line?
I would be interested in a waterproof model so I can mount it right on the antenna mast.
I looked at several on AES. Looks like under $50.

When I was putting up my Ringo Ranger ARX-2B, I considered waiting another week or two so I could buy a lightning protection device, but decided to put it up without, as I will be disconnecting my radio when its not in use.

I appreciate your mention of storms that "sneak up" on you. That almost happened to me today, as I was listening to the radio and heard a rumble of thunder. I had been watching radar on Weather.com, and saw the storms passing to my north. It was not very close at all but I disconnected the radio.

As far as the DC shorted antenna system, while it might not help for a lightning strike, wouldn't there be a DC component to the current that flows continuously during a storm?

Thanks

FW

 

[OceanaRadio]

FW,

Sure there is a lot of DC in both the pre-storm blanketing of +ions, the streamers themselves, and perhaps thousands of DCV from a connection to a cloud. Considering the cloud-to-ground potential is in the millions of volts, a few hundred or thousand volts of DC protection misses the point from a risk-management prospective. As to streamers and ground-level +ions, there is nowhere to "drain" those pre-storm charges because they cover everything, all surfaces, from earth to several hunded feet above ground. While such ionization tends to equalize across all outdoor surfaces, it can still behave remarkably such as "flash visibly" from sharp-corner objects into air space. I do not know if that gathering of +ion streamers, or the massive energy from nearby-strikes are responsible for exceeding the dielectric value of a disconnected coax, but I have observed carbon-tracks from arcing between the center-conductor and the threaded (shield) connector.

In theory, a DC-grounded antenna could minimize some damage from low-level energy, so I don't want to make it sound useless. Just don't let anyone tell you it (alone) can save the day in a direct or very close attachment from lightning.

As to personal preference in surge arrestors, I think the I.C.E. (Industrial Comnunication Engineers, Ltd) company makes the best protection gear. They use a multi-level defense to incoming surges that includes a static-drain on the center-conductor (yep there's a little DC ground, ha ha), a strong inductor for the next few thousand volts, and finally the gas-tube for as much as any coax connected to it could carry.

It's important to remember that no surge arrestor is built to survive more than the breakdown voltage of the coax it is designed to mate with can carry . Most coax used in our work will be 3/4" hardline/heliax or less, and those breakdown at or less than 8,000V. RG-8 breaks down at less than 6,000V and house wiring breaks down at around 3,000V. Proper shield-grounding of coax before it gets to an arrestor/surge protector further limits what will be delivered to the arrestor even in a direct attachment to the antenna. Thus any properly designed arrestor can do it's job when the requisite bonding and grounding design are in place. Unfortunately the arrestors all work just fine in reverse, which means that they will unwittingly help deliver a whopping several thousand volt surge from your power company's electric lines right through the radios on it's way into your convenient outdoor grounding system. When guys sink a single rod for a rooftop or treetop or other outside antenna, and then forget to bond that ground rod to the AC entrance ground rod, this is beggging for the example just given to happen. It can happen anyway if the bond is too far, or there is no AC surge protection at the AC meter or entrance panel.

Hope this helps.

J

Good post Jack;
Do you have any recommendations for lightning/surge protectors for the feed line?
I would be interested in a waterproof model so I can mount it right on the antenna mast.
I looked at several on AES. Looks like under $50.

When I was putting up my Ringo Ranger ARX-2B, I considered waiting another week or two so I could buy a lightning protection device, but decided to put it up without, as I will be disconnecting my radio when its not in use.

I appreciate your mention of storms that "sneak up" on you. That almost happened to me today, as I was listening to the radio and heard a rumble of thunder. I had been watching radar on Weather.com, and saw the storms passing to my north. It was not very close at all but I disconnected the radio.

As far as the DC shorted antenna system, while it might not help for a lightning strike, wouldn't there be a DC component to the current that flows continuously during a storm?

Thanks

FW

 

[CSXRiverline]

Hi Jack;
I ordered the I.C.E. 302U today.

My grounding system is per NEC, with #4 THHN running from the clamp on the mast down to the SE ground conductor a few inches before it attaches to the ground rod.
I don't have any additional ground rod for the antenna, but my run for the ground is less than 50ft, and the SE ground is also bonded to the water main at the meter.

I appreciate your good advice.

Thanks

FW

FW,

Sure there is a lot of DC in both the pre-storm blanketing of +ions, the streamers themselves, and perhaps thousands of DCV from a connection to a cloud. Considering the cloud-to-ground potential is in the millions of volts, a few hundred or thousand volts of DC protection misses the point from a risk-management prospective. As to streamers and ground-level +ions, there is nowhere to "drain" those pre-storm charges because they cover everything, all surfaces, from earth to several hunded feet above ground. While such ionization tends to equalize across all outdoor surfaces, it can still behave remarkably such as "flash visibly" from sharp-corner objects into air space. I do not know if that gathering of +ion streamers, or the massive energy from nearby-strikes are responsible for exceeding the dielectric value of a disconnected coax, but I have observed carbon-tracks from arcing between the center-conductor and the threaded (shield) connector.

In theory, a DC-grounded antenna could minimize some damage from low-level energy, so I don't want to make it sound useless. Just don't let anyone tell you it (alone) can save the day in a direct or very close attachment from lightning.

As to personal preference in surge arrestors, I think the I.C.E. (Industrial Comnunication Engineers, Ltd) company makes the best protection gear. They use a multi-level defense to incoming surges that includes a static-drain on the center-conductor (yep there's a little DC ground, ha ha), a strong inductor for the next few thousand volts, and finally the gas-tube for as much as any coax connected to it could carry.

It's important to remember that no surge arrestor is built to survive more than the breakdown voltage of the coax it is designed to mate with can carry . Most coax used in our work will be 3/4" hardline/heliax or less, and those breakdown at or less than 8,000V. RG-8 breaks down at less than 6,000V and house wiring breaks down at around 3,000V. Proper shield-grounding of coax before it gets to an arrestor/surge protector further limits what will be delivered to the arrestor even in a direct attachment to the antenna. Thus any properly designed arrestor can do it's job when the requisite bonding and grounding design are in place. Unfortunately the arrestors all work just fine in reverse, which means that they will unwittingly help deliver a whopping several thousand volt surge from your power company's electric lines right through the radios on it's way into your convenient outdoor grounding system. When guys sink a single rod for a rooftop or treetop or other outside antenna, and then forget to bond that ground rod to the AC entrance ground rod, this is beggging for the example just given to happen. It can happen anyway if the bond is too far, or there is no AC surge protection at the AC meter or entrance panel.

Hope this helps.

J

 

[richardc63]

Always an interesting subject

It is good to read the variations in approach to this issue. I've found that it stirs up more friendly disagreements among techs than any other issue, probably because none of us fully understand everything there is to know about lightning behavior.

I work for an agency with a few hundred firestations, almost all of which have a 40-50ft hose drying pole with a 148MHz colinear at the top for their turn-out paging. I was involved in the lightning protection & grounding design for these installations. We broadly followed what many call the "Andrews" recommended practice that most techs would have. That is we used these basic rules:

1. Surge suppressors (Polyphasers) mounted on an earthed cable entry plate, usually under the eaves (almost always full brick buildings), a 40mm multistrand earth lead straight down the wall to an earth stake.

The purpose of (1) is to deal with the majority of the current, with the antennas, external cables & surge suppressor expected to be sacrificed in the event of a strike.

2. The earth stake is also bonded via a 4-6mm multistrand conductor following the shortest practical path to all equipment racks.

The purpose of (2) is as an "equi-potential bond" to deal with the massive potential difference generated in the equipment as a result of the strike. It is not intended to carry the current (hence the much lighter conductor) but to try to keep all components at the same ground potential.

We should earth our poles as well, something I'm trying to do on new installs, but unfortunately many are in urban locations (concrete etc) & there is a reluctance to retrofit proper pole grounding (and fitting of a grounding kit to all feeders).

The best way to assess whether anything works is to witness the outcome of a strike. I've seen a couple, and it worked. The colinear was reduced to shards of fibreglass, the LDF4-50 was beautifully welded internally (I even witnessed the scorch marks where said feeder ran along a metal surface), the RG214 on the inside of the Polyphaser was totally unaffected and the equipment suffered nothing more than blown fuses- though we retire any equipment that goes through such stress.

I've also seen what happens when good practice isn't followed- and the damage is far far worse. The worst I see, sadly too often, is the lazy practice of mounting surge suppressors IN the equipment rack and then grounding the rack. I've seen such installs cause damage to those agencies who share the hut & rack with them... much like extending the welcome mat to lightning to "hit me". The bottom line is that in shared sites there must be one rule for all (and this can be applied to a home install with all feeders needing to be dealt with identically).

Cheers,


Richard

ps My apologies for the metric references in cable sizes- I don't have the AWG equivalent handy.

 

[CSXRiverline]

richardc63; Very interesting post.

Besides what I have, and will have on my new antenna install, I already have a whole-house unit located on my SE panel.
I also use POU surge outlet strips for all of my electronics.
Nice though, my 2m radio is a handheld, and most times is not connected to the AC mains, so at least that POE is eliminated.

FW