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Ham Radio Antenna Lightning Strike - WHAT HAPPENED??
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- เผยแพร่เมื่อ 3 ก.ค. 2019
- My Comet dual band antenna got struck by lightning. But what puzzles me is that the coax and radios it was attached to are fine, even though it wasn’t grounded.
I seek the expertise of the YT audience to help me on this one. I ask a few question at the end of the video and appreciate anyone’s insights.
Thanks for watching, cheers and 73s
I used to be a radio installation engineer for Racal many moons ago, and have seen a few 'blasted' antennas like this. Yes, it was a direct strike; the current fuses the antenna element and the metal vapor expands very quickly, causing the radome to explode, (a bit like you see trees explode when hit; the sap boils to steam in an instant and expands, shattering the tree). The burns you see on the side of the mounting are where the current has flashed sideways to the mounting, and into your stone wall, which at that location will conduct electricity to ground better than the feeder.
Because your radio presents what is effectively an earth at the top of the antenna, that is the lightning's first point of contact. If the conductive path through the coax has a higher resistance to ground than an adjacent conductor, or presents inductive impedance, the voltage at the base of the antenna rises very high, very quickly. As it gets above a certain voltage, there will be a discharge to the next-best-ground conductor, and you will see a side-flash.
For your new installation, run a flat copper ground tape from the base of your antenna to a suitable earth-spike at the base of the wall, with as few kinks and curves as possible; connect the feeder coax outer to the same earth spike. Fit a lightning arrester to the feeder where it enters the house.
Disconnect your antennas from the equipment when there is a storm in the area.
Thank your lucky stars that the house didn't burn down!
Good luck.
This guy gets it. If have to hazard a guess that this was a negative lightning strike. Had it been a positive strike, it's likely that there would be no antenna and a significant chunk of stone would either be vaporized or lying on the ground.
PS. I don't know the EXACT specifics about different lightning charges, but if memory serves me right. You could survive a negative strike, but won't survive a positive strike. Positive strike have an obscene amount of current.
Yes and absolutely no.
I've been an electrician for 34 years and have done a bit of tower and antenna work.
First, it is NEC code to have a listed lightning arrestor, before it enters the building, on ALL feed-lines and or wires to ANY antenna. Failing to follow this will find you denied any claim under your homeowners insurance, should damage occur.
Putting a ground rod at the bottom of the antenna with a lightning arrestor and calling it a day is worse than having no ground at all!! (Emphasis added)
There is a difference between "grounding" and "bonding". Using a separate ground rod for the antenna, independent of your utility ground, can develop 10's of millions of volts or 100's of millions of volts for a direct strike! The answer is simple ohms law. The difference in potential between two separate ground rods is enormous! (E= I X R) The average lightning strike is around 300 million Volts at around 30,000 Amps!!!
You NEED to bond the ground rod below your antenna to your house utility ground with a minimum of 6 awg, stranded, copper wire with ground rods spaced about twice their length (ex. 8" ground rods should be placed about 16' apart) and you need a single point ground system, never two separate grounds! Ever!
You also need to bond all of your antennas together with copper strap (see DX Engineering or Georgia Copper) or at least 6AWG stranded, copper wire (but I'd recommend 4AWG).
Please 🙏 never, ever, under any circumstances whatsoever add a second ground rod, unless bonded to your utility ground. This could be a very expensive and fatal decision!
Hey man, I'm grounding a 9 inch, solid copper Hnt antenna to the top of my roof to the side of the house, can I ground it without a lightning arrester? There's no way to connect a lightning arrester since the cable of the antenna is imbued or manufactured directly into antenna w/o the option to add an arrester, so anyways, I'm bringing a 20 ft solid 10 gauge copper wire down to the 8ft copper pipe I just hammered down 7 ft into the ground, that should suffice right? The wire is directly connected to the (copper)grounding rod and up to the base of the antenna, wrapped around that is. Thanks for your time, question is, does that suffice? Thanks.
@@timmack2415 @Tim Mack Hi Tim, Hope you are still on TH-cam and doing well.
I read your comment with great interest and have some questions.
As you know the NEC is a huge document. I couldn't find the requirement for amateur radio feedlines to have a listed arrester. Could you cite chapter and verse or at least chapter so I can study it? Arresters and feedlines clearly aren't going to withstand a direct hit but may attenuate the effects of a nearby strike and also help with static.
Next, why do you favor stranded #6 or #4 bonding wire between ground rods vs solid wire of the same gauge? Is it for edge effect and is that what code requires? How deep do you bury the wire?
When you say all antennas have to be bonded together, you mean their ground rods, correct?
I looked up copper strap and it comes in various widths and thicknesses. What thickness and width do you or the NEC recommend/require for bonding ground rods? I don't know the strap measurements that would correspond to #4 or #6 stranded wire. Maybe it's in the code and I just didn't find it.
Not mentioned in all of this is the radio, PSU, etc.
I have seen some interpretations of the code that argue station grounding is not required because it is grounded through the 😮house circuitry to the mains ground.
However the majority would have us run short 1 inch wide copper braids in parallel from each "box" to a common copper bus. A single copper braid extends from the bus to a copper strap to a ground rod that is bonded to the service entrance ground as you describe. In your opinion and experience, which is correct?
Finally, how do I find an electrician or engineer as knowledgeable as you near me? What do I google? Not all do this kind of work or consulting from what I can tell.
Kind regards,
John
I lost 2 to $3k in equipment from a lightning strike a half mile away. It was such a big hit it disintegrated the tree. Streamers can create voltages in an area...not just a direct hit. Your very lucky you didnt suffer greater damage. Yet losing any $10 piece of equipment sucks. Thank your rock work, it may have saved you from fire.
Lucky you, coax and radio wise. My Comet GP-9 was hit a couple of days ago, (5/17/23) and it took out my antenna, coax and a radio. Strangely, the antenna mast was grounded and there is a lightning arrestor connected between the coax and feed line going into the house and is also grounded on a separate rod. The lightning arrestor doesn't look like it did anything at all. As far as a direct strike goes, I think, since your antenna damage looks very similar to mine, is that we may have been hit with one of the streamers of a direct lightning bolt.
I believe the antenna exploded and basically shorted before the lightning got to travel down the coax. I would run a ground wire from the metal mast up there to a ground rod, this will act as a lightning rod to absorb and dissipate any future strikes. Yes, unplug the coax when not in use.
Good illustration and good comments. THanks
Nice castle
Lightning path is stange. Last year, our amateur radio tower got struck, wires conducting 220 volts electricy smashed to uncountable pieces, power meter smoked. Weired enough, the shortest 4.2 meters fiber antenna was the only one attacked by lightning bolt while two longer 6.5 and 7.2 meters fiber antenna were totally fine. All repeaters were grounded, but only the APRS repeater connected to the short antenna was destroyed. I searched for many videos regarding lighting hitting tall buildings, finding that sidewalls many storeys below the top probably get struch too. So I think, the path of direct strike can be sometimes beyond anticipation.
I know this is a little old but I didn’t see it in the comments so I’ll throw my $0.02 out there.
I’m no electrical engineer as well, but I’m in the middle of setting up my shack and have been reading a lot on proper grounding to protect against lightning. The most resounding thing I keep reading over and over is that there is virtually now way to 100% prevent a direct strike, but there are things you can do to minimize the risk. Those things are 1) grounding your antenna mount and 2) grounding the coax by utilizing something like a lightning arrester.
Lightning is essentially a MASSIVE example of the same thing that happens when you get a static electricity shock. If your antenna is not properly grounded using lightning arresters your antenna can build up quite a bit of static electricity. If the conditions are right for lightning and your antenna has a massive amount of static electricity built up, this cause cause your antenna to become the path lightning to get to ground. I would imagine that is why your antenna received a direct strike rather than the pole next to it.
Excellent video. I subscribed. Get yourself a polyphaser and put it in your coax cable! God bless.
I had a V2 2 meter antenna whitch was hit by a main lightning strike. The fiberglass antenna looked like a bird with feathers after the lightning strike. In my opinion, fiberglass antenna attract lightning. I use antennas with gamma match now.
the antenna was dc grounded which means the lightning strike hit the antenna and went to ground before your coax.
He said it wasn’t grounded.
@@dcentral dc grounded and grounded like you would say a serious 2016 are not the same thing.
If you look at the makeup of the antenna at the very bottom you will find a few capacitors. Some of the capacitors couple to the inside of the coax through the so239 fitting. BUT, the others couple to the metal of the outer normally grounded parts of the antenna. I suspect those capacitors are now more like solid wires, melted together ? Are you saying you didn't have the pipe that the antenna was mounted to going all the way to the ground ? Or at least a wire going to ground ? Typically the majority of the lightning pulse would jump through the capacitors in the bottom of the antenna out to ground, "taking the shortest path to ground" is the general rule. I've had it jump right out of the center of coax that was laying on concrete and into the concrete ! Shortest path was down to the ground (concrete) and not into the radios. That said, the controller of the repeater had a problem which I repaired and we were back in business ! We now use "POLYPHASER LIGHTNING PROTECTION" parts with ground rods ect.
wow dude some good info. how interesting. .thank you for posting.. n0amy.
good video thanks for posting
Did you have a lightening arrestor between antenna and coax?
Dick Grantberg Well perhaps the metal roof did act as a large ground to dissipate the energy, who knows. Lightening behaves so unpredictable that there are all sorts of theories and opinions on right and wrong protection. I would at minimum invest in a good lightening arrestor just to add a layer of protection and hope it works.
WTH bro you live in a castle
he's american his great great great great great great grandfather was Irish and lived in a castle.
Does your antenna still work? Doesn't look that bad to me. My cars are ugly but still work. You shouldn't judge an antenna by a few blemishes and a few signs of normal wear and tear.