Whats this coax in a fruit jar stuff?

[Captain Kilowatt]

Don't get hung up on the term "lightning arrestor". A lightning arrestor's job is to shunt damaging voltage spikes to ground and limit the potential for damage.Yes they do bleed off static but without the static being bled off the potential for a strike is MUCH greater.The picture above of the Polyphaser unit is interesting and typical of all decent units. It has DC blocking,the two wires that are connected to the antenna jacks form a capacitor that allows RF to pass but not the DC electrical energy.The small coil allows for the DC enegy to pass through to the gas discharge spark gap that is grounded yet exhibits a high impedance to any RF.All in all not a bad concept.Simple yet effective.

dont people just unscrew there coax during a storm anymore? its not rocket science.

And what happens to the end of the cable when lightning does hit? You do realize that the insulation on a piece of coax is only good for a few hundred to a few thousand volts don't you? Imagine around a half a million to a million volts coming down that coax cable looking to get out. If it does not find a path out it WILL make it's own. Simply laying a disconnected cable over the desk or on the floor will not protect anything that is nearby in the event of a direct strike.Several years ago a friend of mine "simply unplugged " his coax as a storm was approaching.Lightning hit his A99 directly and it just plain disappeared. :shock: Unfortunatly so did a large piece of his kitchen cabinets and wall where the coax was routed. Lawson was thrown across the kitchen. He had been leaning against the counter near his radio.What good did unplugging the coax do to him? A lightning arrestor MAY have prevented the strike in the first place by bleeding off the charge that was building up on the antenna and certainly would have reduced the damage done if a strike had occured anyway by shunting some/most of the energy to ground.It was interesting to note the structural damage to the house was NOT at the antenna mounting point but rather inside the house walls along the path of the coax cable.At least that's what the fire dept. told him.Some hams I know have lost a good HF rig even when the coax was unplugged and laying near the radio. The surge induced in the cable took out the radio without even being connected to it. Does this happen all the time? Certainly not. Can it happen at any time. Certainly so.You are right it is not rocket science but it is a good lession in physics.Trust me I used to simply disconnect the cable and throw it over the back of the desk as well. Then as a broadcast engineer I started to learn more about what happens during a strike both direct and induced and I changed my mind. I had a strike many years ago that I am sure struck the tower. It was during a sever storm and I saw the flash,heard and felt the BOOM that rattled the windows, and actually heard the frying sound of the dischage from inside the house.All three things happened at exactly the same time and the flash was at the end of the house where the tower was.I found no damage to the tower or antennas but some ground was torn up around the tower base near the ground rods.I still think I was lucky dispite my preventative measures that worked.You may get lucky and never have a problem but the reason is not because unplugging the cable was the cure.It was simply because you were lucky. If you have ever seen the aftermath of a direct strike you will know what I mean.Twenty two years in the business with a total of 14 towers in the air,yep I saw some damage.I was also lucky considering what could have happened.

 

[Cat Driver]

Good idea????

Thought about putting another grnd rod a coupla ft from my radio grnd rod an then soldering the shield and center of a # rg58u to it. Then I'll run it into the house an use a barrel connector to hook it to my base antenna coax coming in when it is gonna storm.
I'll probably ground the antenna tripod an mast also to another rod right below it. This is a dc grounded Maco V-58, so I guess grounding it won't hurt anything will it?

Thanx,
Ronnie

 

[C2]

yea, that is what I said too. ground it outside through a switch or grounded connector. The only thing better that I can think of is to take the antenna down.

Oh yea, but I would not route the cable through the house, then back out to ground. Why bring the lightning inside?

There are really good switches that you can have outside, or better, just mount a bulkead connector to the side of your house and remove the coax there to ground.

 

[Captain Kilowatt]

Grounding outside the house good. Looping through the house first bad. In some cases it is next to impossible to completly remove the coax from the house and that is where isolating the end AND grounding the crap out of things including using a lightning arrestor becomes necessary.

Good info on Grounding a ham station from Polyphaser

and from the master page the above link came from Polyphaser Technical notes

 

[TonyV225]

best in the world in my opinion but is a pain in the arse is to do what I used to do and DISCONNECT AND I PUT A BAGGY OVER THE PL259 WITH A RUBBERBAND AND OUT THE WINDOW IT WENT WITH THE PL259 POINTING AWAY FROM THE HOUSE...I also left a few larger loops in the coax before it entered the house incase i wasnt home or I forgot to disconnect and put it outside. remember no matter what you do if lightnings gonna hit ITS GONNA HIT. Best setup was the line I made up with a shorted pl259 end that was connected to a 9 foot ground rod outside the wall behind my desk I would just connect to that through a lightning arrestor that was also grounded with a thick ground solid core wire also had loops outside but again if I wouldve been hit who knows maynot have helped anyways. Throwing coax on the floor isnt the brightest thing when lightning comes down and comes to the end its shooting out to the first ground and taking out what and whoever is in its path like a gun. Ide feel better atleast trying to send it in a curtain direction or atleast knowing where its flying before your attacked by it. Just my 2 cents but as I said the safest I ever felt was laying it out of the house where there was plenty of ground in the opposite direction of the house .

 

[Hamin' X]

An ounce of prevention is worth a pound of cure.

Why would you want to ground everything and attract more lightning? Have you ever heard of "lightning rods"? The purpose of lightning rods is to attract lightning to one point and route the current to ground. However, at the voltage and current levels that we are talking about, this brute force method is certain to fail.

A simplified description of lightning:

The clouds form a massive static generator, due to the friction of dust and ice crystals. This causes a layer of negative ions to concentrate in the lower levels. This concentration of negative in the clouds, forces positive ions to congregate on the surface of the earth and to flow up towards the clouds though anything that they can find (Trees, hilltops, YOUR TOWER!). Once these charges reach a certain level, an ionized path opens up and allows the main charge to travel to the object and into the ground.

The cure is to ground everything so well, that all of the charge is carried to ground and not through your equipment. This greatly increases your chance of a strike and if anything goes wrong in your grounding system (and it will), you will have meltdown.

The prevention is to dissipate the positive charge accumulating in your tower BEFORE it reaches the critical level. use a device such as this, available from: The Wireman

Similar systems are used on aircraft and sailboats. I also use them on my repeater towers, located on mountain tops.

Rich

 

[Captain Kilowatt]

HaminX not sure where you get the idea that a lightning rod's job is to attract lightning to a certain spot. A lightning rods job is to bleed of a charge before a strike can occur.If it fails to do so then at least the strike that does occur is hopefully routed to ground.

The cure is to ground everything so well, that all of the charge is carried to ground and not through your equipment. This greatly increases your chance of a strike and if anything goes wrong in your grounding system (and it will), you will have meltdown.

Again, grounding reduces the chance of a strike,not increases it. If things are grounded properly then no meltdown will occur. Heat is caused by high current and a poor connection. Obviously the lightning is high current but if the connections are good then the current should flow to ground without a problem.

Tnx for the link to the static disipater BTW. I knew about them but forgot where I saw them. They sort remind me of a steel wire chimney cleaning brush.

One thing to remember is that it is a good idea to have a turn or two in any cables coming into the house but DO NOT COIL THE GROUND LEAD. The ground should be as short and direct as possible with no sharp bends.

 

[park]

I knew the grounded vs not grounded debate was coming !

Aircraft very rarely get hit by lighting, because their not grounded ??

But if they don't have enough static wicks they (the aircraft) can discharge a large amount of static and cause damage to the aircraft.

 

[Hamin' X]

HaminX not sure where you get the idea that a lightning rod's job is to attract lightning to a certain spot. A lightning rods job is to bleed of a charge before a strike can occur.If it fails to do so then at least the strike that does occur is hopefully routed to ground.

Simple physics. Lightning will strike the object with the most positive charge, closest to the most negatively charged layer in the cloud. Even though this was not understood when Franklin invented the lightning rod, it worked very effectively. The lightning would strike the rod, instead of the structure, because the ground wire gave a low resistance path to the rod for the positive ions building up on the surface of the earth. After being attracted to the rod, the charge would be carried to the ground without damaging the structure. When people started to put multiple rods on the roof, a strange phenomenon was observed. The structure was no longer being struck by lightning, even though it was the tallest thing around. by adding more points the positive charge was being bled off before it could reach a critical level. This is the same principle as the porcupine, static wick, static buster, or whatever you want to call it, works on.

Again, grounding reduces the chance of a strike,not increases it.

Just the opposite is true. See above.

If things are grounded properly then no meltdown will occur. Heat is caused by high current and a poor connection. Obviously the lightning is high current but if the connections are good then the current should flow to ground without a problem.

A true statement, but the devil is in the details. Typical lightning bolts are in the range of 30,000-50,000 Amps and can reach potentials of several million volts. As you can see, even the smallest amount of resistance in your grounding system will lead to tremendous heating and/or failure. A grounding system is not "install and forget". It requires constant inspection and maintenance to remain effective.

Remember: Ground wires give a path for the positive ions from the earth to travel up your structure. This positive charge "attracts" the lightning bolt. If you provide many sharp points for the positive ions to dissipate from, your structure is less likely to reach a strike potential.

Tnx for the link to the static disipater BTW. I knew about them but forgot where I saw them. They sort remind me of a steel wire chimney cleaning brush.

Your welcome. I make my own from stanless steel cables.

One thing to remember is that it is a good idea to have a turn or two in any cables coming into the house but DO NOT COIL THE GROUND LEAD. The ground should be as short and direct as possible with no sharp bends.

Also, good advice. I have found that using "drip-loops" with the bottom near a ground plate, connected to multiple ground rods is effective. Also, use only one grounded entrance for all of your coaxes and control cables.

Lightning safety is not to be fooled around with, or approached in a haphazard manner.

Rich

 

[loosecannon]

wow there are a lot of myths floating around about this subject!

seems more misunderstood than SWR.LOL

the way to determine what is myth and what is fact is to look at commercial broadcast sites.

they have big, tall towers up on mountain tops, far, far away from any manned transmitter.

do you guys think they are not grounded?
do you think they disconnect the coax during storms?

do you think they even give it a second thought?

of course they dont. because their equipment, (over 100,000 watts, and millions of dollars) is protected by sound engineering and physics.

they use lightning protection in the form of products like those that polyphaser makes.

if you were the owner of a big time radio station, and you knew that if you were knocked off the air by lightning for even an hour that you would be losing LOTS of money; then you would damn sure make sure that your investment was protected.

these products work, as can be attested to by the people i know who had either indirect or direct hits, and sustained no damage to their radio equipment, even though the antenna was in a million pieces and the coax was melted.

i have a pic of a lightning arrestor after it took an indirect hit.
it wont show up on the forum, but the thing is TOAST!
this person had a polyphaser product inline, and his equipment was just fine.
loosecannon

 

[Hamin' X]

Comparing a broadcast site to the typical amateur, or CB installation, is a rather specious argument. As I stated in my previous post, the devil is in the details.

If you want to go the brute force route of the big boys, have at it. However, most of us don't have the money, time, or expertise to pull this off. I don't know about you, but my station generates very poor cash flow.

Grounding and protecting everything is a great way to go, but it is very expensive and if not done right, or properly maintained, will make you worse off than doing nothing. Just driving a ground rod into the ground and attaching a grounding cable to it with a clamp, ain't gonna cut it. You have to have multiple ground rods and the wires must not only connect to your tower, but connect the ground rods together. Also the ground rods must be driven to a level below grade. Now your connections are underground. Do you Cad Weld your connections. Did you have a site survey done to determine the soil type and conductivity? If you did not, then you have no idea how much of a ground system you need.

More later, if needed.

Rich

 

[Captain Kilowatt]

Well Hamin'X it seems that we agree on pretty much everything except I believe the MAIN purpose of a lightning rod is to first bleed of any charge potential and THEN direct a strike if it occurs to ground.Dual purpose,not to simply shunt a strike as a primary purpose. You actually confirmed that by saying

When people started to put multiple rods on the roof, a strange phenomenon was observed. The structure was no longer being struck by lightning, even though it was the tallest thing around. by adding more points the positive charge was being bled off before it could reach a critical level.

Perhaps we believe the same thing but are expressing it in a differant way.


loosecannon wrote:

the way to determine what is myth and what is fact is to look at commercial broadcast sites.

they have big, tall towers up on mountain tops, far, far away from any manned transmitter.

do you guys think they are not grounded?
do you think they disconnect the coax during storms?

do you think they even give it a second thought?

of course they dont. because their equipment, (over 100,000 watts, and millions of dollars) is protected by sound engineering and physics.

they use lightning protection in the form of products like those that polyphaser makes.

if you were the owner of a big time radio station, and you knew that if you were knocked off the air by lightning for even an hour that you would be losing LOTS of money; then you would damn sure make sure that your investment was protected.

these products work, as can be attested to by the people i know who had either indirect or direct hits, and sustained no damage to their radio equipment, even though the antenna was in a million pieces and the coax was melted.

i have a pic of a lightning arrestor after it took an indirect hit.
it wont show up on the forum, but the thing is TOAST!
this person had a polyphaser product inline, and his equipment was just fine.

Look at my profile under occupation. 22 years at it.

 

[nightwatch]

I Think that's an old wives tale

 

[loosecannon]

good points from everyone.

hammin x, i agree that not everyone can afford to do the broadcast type setup, but the real world examples i have seen where the polyphaser product saved the radio equip. were not pro setups, just cb/ ham setups.

i believe this to be the case, if i am wrong i will happily accept any corrections:

the antenna and support structure should be connected to a ground rod with 4ga. solid copper wire or strap.

the station equip. should be grounded to a ground rod, and this rod should be tied together with the other.

the AC house wiring should be connected to a ground rod, and this rod should be tied to the others.

the coax coming from the antenna should be connected to a "polyphaser" just before entering the shack, and the polyphaser should also be tied to one of the ground rods.

i have two friends with setups similar to this, that both run klv 1000's, both took a lightning strike, one guys imax exploded.
the other guy ran a maco v5/8, with a "lightning arrestor" attatched to the SO-239.
the SO_239 was toast as was the arrestor, and the coax going into the polyphaser.

neither one lost any equipment or sustained any damage to their radio equipment.

good discussion guys!
loosecannon

 

[Hamin' X]

Well Hamin'X it seems that we agree on pretty much everything except I believe the MAIN purpose of a lightning rod is to first bleed of any charge potential and THEN direct a strike if it occurs to ground.Dual purpose,not to simply shunt a strike as a primary purpose. You actually confirmed that by saying

When people started to put multiple rods on the roof, a strange phenomenon was observed. The structure was no longer being struck by lightning, even though it was the tallest thing around. by adding more points the positive charge was being bled off before it could reach a critical level.

Perhaps we believe the same thing but are expressing it in a differant way.

Actually, I did not confirm your statement. The problem is with having enough sharp points to dissipate the positive charge fast enough to remain below the critical discharge level. Perhaps you have seen some old tin roofs with a ridge cap that looks like a saw blade. This performs the same function as the dissipators, or multiple lightning rods. The operative point here is, Multiple.

Many broadcast towers, particularly Cell, FM and TV, have multiple antennas on them. If you have ever noticed, most commercial antennas have a sharp point on the end, or a pointed cap on the mast of multiple bay antennas. These act as dissipators. The positive ions will even travel up the outside of fiberglass antennas and really don't care much whether your grounding is low ohmic or not, because of the high impedance nature of the charge. The towers that are the hardest to protect are the AM broadcast towers that are on insulated supports and have insulated guy wires.

QRN, I respect your expertise as a broadcast engineer, but you come from the prospective of; insert more money and buy the best protection for the equipment. In your line of work, with very expensive equipment and down time is lost money, this is necessary. My perspective comes from; 30 years of building installing and maintaining commercial and amateur repeaters. Mainly on rocky mountain tops here in the Northwest. Most of these sites are only accessible 3-4 months out of the year and the Bell Jet Ranger is not an option. Also, there is very limited grounding available, as the soil is only a few inches deep. I do maintain a repeater at an old AT&T site, which used to be and old Air Force Radar station for the DEW line. This site has a massive trench surrounding it, filled with gravel and a chemical slurry to provide a sufficient grounding system. However, it is starting to fail and I have noticed the noise floor raising and an increase of "precipitation static" on my 2m repeater. Come summer I will isolate my tower from the grounding system and go with dissipators.

I go back to my original statement: An ounce of prevention, is worth a pound of cure.

Rich