On a recent trip to China I photographed a number of "antennas" that I do not recognize. Are they even antennas?
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1$\begingroup$ Hello and welcome to ham.stackexchange.com! $\endgroup$– rclocher3Commented Jul 30, 2020 at 13:58
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1$\begingroup$ Lightning rods? Or lightning-repelling rods (there's no such thing but people try)? $\endgroup$– tomnexusCommented Jul 30, 2020 at 20:31
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1$\begingroup$ @tomnexus Lightning rod, yes; and nope, we can't repel lightning and make it retreat back up into the cloud. :-) $\endgroup$– Mike WatersCommented Jul 31, 2020 at 2:05
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$\begingroup$ It could help to know precisely where these pictures were taken. $\endgroup$– Phil Frost - W8IICommented Jul 31, 2020 at 17:52
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$\begingroup$ Both devices were seen in Kunming, Yunnan. I can't be more precise than that. $\endgroup$– VE3LNYCommented Aug 3, 2020 at 22:05
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2 Answers
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A possibility for their use is suggested by the small "globes" at the free ends of the conductors in the 2nd photo. If this array of conductors was intended for lightning protection, they better would have very sharp tips in order to reduce the flashover voltage appearing at the ends of the conductors. Also, ~vertical conductors would be better for lightning protection, as they would better protect the structure to which they are attached.
Instead those conductors might be co-driven radiators of a semi-wideband, ~directional antenna system.
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1$\begingroup$ Those free-end "globes" look more like a few sharp "probes" to me. Exactly as you suggest, for corona discharge. $\endgroup$ Commented Jul 31, 2020 at 14:39
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$\begingroup$ Nice answer. If you click on the bottom photo to enlarge it, those globes appear to be where the short fine wires -hopefully with very sharp ends- are attached. $\endgroup$ Commented Jul 31, 2020 at 17:25
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Those are not antennas, but intended to be lightning dissipators. Basically, they are a type of lightning rod.
A lightning rod or lightning conductor (UK) is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through a wire, instead of passing through the structure, where it could start a fire or cause electrocution.
The following related questions and answers go into more detail:
The lightning dissipator consists of many small spikes and prevents a strike by slowly discharging through each little spike.
Do lightning rods attract or do they help prevent lightning?
https://physics.stackexchange.com/questions/65825/does-a-lightning-rod-prevent-lightning-strikes
How does a higher antenna reduce rain static on a lower antenna?
In summary, several answers support that they can prevent a lightning strike under some circumstances. Others disagree and vehemently declare that they are of no value whatsoever. I strongly believe that the truth lies somewhere in the middle.
On top of this corona-discharge negative ion generator is an effective (if fragile) ion emitter, which appearance and function is very similar to those photos in the question. There were actually eight of those .005" diameter stainless steel wires.
(No longer manufactured)
answered Jul 31, 2020 at 1:55
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1$\begingroup$ But but all of the articles you link to say there's no way to divert lightning or reduce the chance of a strike. I also wrote an answer about it. I do agree that's what these things in the picture are. $\endgroup$– tomnexusCommented Jul 31, 2020 at 3:37
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$\begingroup$ "In summary, the consensus is that they can prevent a lightning strike, under some circumstances." The only article you linked which seems to support that consensus is one you wrote. $\endgroup$ Commented Jul 31, 2020 at 4:41
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$\begingroup$ After prolonged thought: I upvoted it for answering OP's question, but I had to leave this comment: The conditions under which these prevent lightning strikes is that lightning strikes suddenly become sentient and pity the fool who spent so much money on these things. $\endgroup$ Commented Jul 31, 2020 at 7:11
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2$\begingroup$ May I suggest sorting this out by adjusting the answer to claim only that they are intended to be lightning dissipators, without claiming they are effective (or not)? That is all that is relevant to answering the question asked. $\endgroup$– Kevin Reid AG6YO ♦Commented Jul 31, 2020 at 18:27
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2$\begingroup$ @KevinReidAG6YO If you don't mind, let's not move these comments to a new chat at this time. Some folks that may have something else to contribute here may not be inclined to visit it. $\endgroup$ Commented Jul 31, 2020 at 20:21