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Offline G0BVZ

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Lightning
« on: January 25, 2014, 14:38:46 UTC »
So there I was, happily operating on 60m when there was a bright blue flash and almost immediately afterwards a loud thunderclap.  The strike will have been between 200m and 300m away, judging by the time between flash and sound.

I dived outside  into a sudden thunderstorm and disconnected the antenna.  This left around 2m of coax going through the wall to the station matchbox. When I got back to the shack a few moments later I heard a GM station slowly become louder and louder to around 599. I had no antenna connected!!

Fascinated, I continued to listen for a short time, then the signal became weak and watery and it gently sank back into the background noise.  I've never heard of lightning affecting propagation like this:  I wonder if the ionised gas of the strike somehow temporarily improved propagation?

I have no idea. -But I an absolutely certain I don't want to hear that effect again!!!!!!

Vic /feeling lucky..... :o

Offline sm5mek

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Re: Lightning
« Reply #1 on: January 25, 2014, 15:05:24 UTC »
Bee careful not to put your tail upwards in those conds.  ;)  Its an furry rising experience, i was once in a thundercloud, that was in the higher mountains in north of SM land, something new, hair was tickeling and tryed to rise. We put our self under an good shelter of some rocks. Some weak cracking sounds but no thunder, it came later over the valleys. (1973)
And yes just after an strike you can if radio remains in good conds hear things normaly not going in, the sientists are talking about "channels" or "thunnel" in the atmosfere. Can also bee an reflection to the cloud. Almost like things in Star Trek.
Best regards, 72 de SM5MEK, Jenny.

Offline G0BVZ

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Re: Lightning
« Reply #2 on: January 25, 2014, 16:18:14 UTC »
Bee careful not to put your tail upwards in those conds.  ;)  Its an furry rising experience, i was once in a thundercloud, that was in the higher mountains in north of SM land, something new, hair was tickeling and tryed to rise.

Definitely a hair raising experience!!  Probably a lucky escape: I'm keeping my tail close to the ground.... ;D

I sent you a message, Jenny; maybe it gets to you.

Vic  /nervous, more storm now.....

Offline IZ5ZCO

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Re: Lightning
« Reply #3 on: January 25, 2014, 20:02:03 UTC »
From Wikipedia:

Quote
Lightning can cause ionospheric perturbations in the D-region in one of two ways. The first is through VLF (Very Low Frequency) radio waves launched into the magnetosphere. These so-called "whistler" mode waves can interact with radiation belt particles and cause them to precipitate onto the ionosphere, adding ionization to the D-region. These disturbances are called "lightning-induced electron precipitation" (LEP) events.
Additional ionization can also occur from direct heating/ionization as a result of huge motions of charge in lightning strikes. These events are called Early/Fast.
In 1925, C. T. R. Wilson proposed a mechanism by which electrical discharge from lightning storms could propagate upwards from clouds to the ionosphere. Around the same time, Robert Watson-Watt, working at the Radio Research Station in Slough, UK, suggested that the ionospheric sporadic E layer (Es) appeared to be enhanced as a result of lightning but that more work was needed. In 2005, C. Davis and C. Johnson, working at the Rutherford Appleton Laboratory in Oxfordshire, UK, demonstrated that the Es layer was indeed enhanced as a result of lightning activity. Their subsequent research has focussed on the mechanism by which this process can occur.


72 de Nicola

Offline GM0LVI

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Re: Lightning
« Reply #4 on: January 25, 2014, 20:31:15 UTC »
It's a bit chancy disconnecting by hand during a storm Vic, but I think I'd probably do if in the same position as you were

Here my antennas are fed by a run of hardline from the shack to a remote 6 way switch box in the garden shed and they are all grounded when not in use. If I hear rumble of thunder I disconnect the phone line from the PC and close down the radios.
I've a friend who had a 3 PC home network and an FT-1000 connected to his phone line, and a remote lightning strike on the line wiped out his PCs and 'degaussed' his radio! Luckily his radio was covered by insurance.
Dave

Offline G0BVZ

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Re: Lightning
« Reply #5 on: January 25, 2014, 23:29:38 UTC »
From Wikipedia:

Quote
In 2005, <snip.....>C. Davis and C. Johnson, working at the Rutherford Appleton Laboratory in Oxfordshire, UK, demonstrated that the Es layer was indeed enhanced as a result of lightning activity. Their subsequent research has focussed on the mechanism by which this process can occur.



Many thanks for the infos, Nicola.  Fascinating indeed but I think I'll leave the research to the researchers!!  Certainly I've never heard anything like that before.  (...and don't want to hear it again.....     ;D)

Vic /not even slightly singed....

Offline G0BVZ

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Re: Lightning
« Reply #6 on: January 26, 2014, 00:05:24 UTC »
It's a bit chancy disconnecting by hand during a storm Vic, but I think I'd probably do if in the same position as you were

Here my antennas are fed by a run of hardline from the shack to a remote 6 way switch box in the garden shed and they are all grounded when not in use. If I hear rumble of thunder I disconnect the phone line from the PC and close down the radios.....

That sounds pretty well thought out.  My antennas change so much it ain't true, but I do have a bird table with decorative roof in the garden: maybe I could put switchgear in that.  My main ant is fed with 300 ohm twin all the way to an unun on the house wall next to a 1" hole left by an obliging plumber when he was working on the house. From there it's 2m coax to the rig so I guess the safety could be built in at that point, but realistically it would only amount to a static bleed.  Nothing on earth can resist a direct strike.

I have several very tall trees on my property that I don't climb any more: all my antennas are glass fibre and are lower than the trees, so I basically hope the they'll attract the lightning in preference to my antennas! ;D  I was concerned to keep the zillion amp spark outta da house though, so I disconnected.

My fone line comes via underground cable and the one in the shack is cordless so that's one thing less to worry about. :D I always disconnect the ant s when not operating: it seems the rational thing to do.

Cheers,

Vic