HGTTG Vogons were "... is useless." Borg are the ones who have "... is futile."

And the Vogon's came first - suggests a little plagiarism by the Borg?

In reply to a post by ian72:

And the Vogon's came first - suggests a little plagiarism by the Borg?

Douglas probably knew Roddenberry well.

In reply to a post by DanielCoffey67:

Are there any devices or precautions I should bear in mind if asking a professional installer to fit a roof mounted pole for a 4G antenna?

Yes - if my experience is anything to go by...

In mid 2000, I paid £40 for the "Ondigital Aerial upgrade". This comprised an enormous Yagi, on the top of tall pole. It joined the gaggle of three other aerials up there.

At 18:01, on the 2nd July 2006 (The Indianapolis F1 race had just started!), said aerial was struck by lightning

Immediately prior to this, I'd been messing with one of these new-fangled Freeview box things, using one of the other aerials. When it started lightning , I pulled the aerial wire out and dangled it over the radiator ... just in case!

The lightning probably hit all 4 aerials; certainly getting the one I had been handling seconds earlier, as a huge flash and a bang filled the room. There was only a little scorch mark on the radiator to show anything had happened, but everything was suddenly very quiet...

It turned out that the lightning had entered the old Samsung NTL/VM box (via the RF input), and had then exited the box, via its ethernet connection and the mains (blowing the 30A trip on its way out of the building).

The aerial itself was remarkably unscathed, though its wiring was no longer intact. Virtually every other piece of electrical equipment in the house was dead though. The insurance claim went on for months!!

(My tv aerial now lives in the loft )

Edited by deleted (Fri 27-Sep-19 00:11:36)

So if it happens again you lose the roof? (At best!)

Sounds like a very unfortunate incident.

As I wrote, we have some mature trees surrounding us that are greatly taller than our building and an immediate neighbour that is a full storey taller than us.

I remember reading that considered across a broad area, lightning strikes on a 50m grid, generally choosing the highest point in that grid. Hopefully we are concealed among much better targets.

There was a Channel 4 documentary, way back in the 80's, where they did some original research into lightning. They found that as the air starts to ionize, 'tendrils' from objects on the ground start to grow upwards, towards tendrils coming down from the clouds. When two of them connect, the current flows...

This probably explains why standing under a tree, to use it as a personal lightning conductor is not recommended...as in, the small tendril from the top of your head, may connect up in addition to the big one from the top of the tree!

(I'm no expert - just fascinated by the subject!)

Edited by deleted (Fri 27-Sep-19 11:46:28)

It should be noted that the purpose of a lighting conductor is NOT to carry the load of a lightning strike to ground but rather to dissipate the build up of charge and thus make a lightning strike less likely. If you still get a strike then it can still be pretty messy.

That's not to say you shouldn't consider putting one in, just that the load rating of the cabling is a moot point if you still get hit. The main function should be to provide a good path from ground up into the sky (reducing the strike risk) and less so a better path to ground in the event of a strike (when damage is likely in any case).

In reply to a post by andyhurley:

It should be noted that the purpose of a lighting conductor is NOT to carry the load of a lightning strike to ground but rather to dissipate the build up of charge and thus make a lightning strike less likely

But isn't the dissipation of the charge, the very definition of Lightning ?

I can see that something tall and spiky might set it off sooner, so it might be a smaller event - but it's still a spark gap, rather than a 'bleed resistor'.

On the subject of what do with the current from a strike: I remember reading that aerial down-leads should be earthed where they enter the building. It didn't seem sensible to me to introduce Lightning into the building (whether via its existing earth wires, or even water pipes). I thought an external length of 45A cooker wire, with all three conductors connected to an earthing rod might be the way to go. I acquired an old GPO rod, but never got as far as implementing it.

In reply to a post by PhilHornby:

... They found that as the air starts to ionize, 'tendrils' from objects on the ground start to grow upwards, towards tendrils coming down from the clouds. When two of them connect, the current flows...

I found a site that backs up what I half remembered from 30 years ago

In reference to www.wunderground.com/resources/education/lightning.asp:

If the negatively charged area at the bottom of the storm gets large enough, sends out a channel toward the ground called a step leader. It is invisible to the human eye and moves in steps toward the ground. When the step leader nears the ground, or a target like a radio tower, it repels all the negatively charged in the surrounding area, and attracts all the positive charge. As the positive charges collect in high enough concentration, they send out small bolts of ground to air lightning called streamers. If the streamers can make contact with the step leader, an electric current wave propagates up the channel as a bright pulse -- lightning!

Also: https://science.howstuffworks.com/nature/natural-dis...
and
https://www.youtube.com/watch?v=P8vqm_ABfqg

Edited by deleted (Wed 02-Oct-19 00:16:09)