Hi Rodney
Probably quite badly.
BUT the relatively low impedance would possibly kill off the 1000V. Assuming you could get this 1000V how would you measure it.
Cheers Bob
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Hi All,
And Because nature is still a mystery, an experiment was done in an area known as âLightning Alleyâ where the team were trying to test various lightning arrestors, and needed to be able to âcollectâ the energy from strikes onto the conductor that was connected to the arrestor. So they strung a heavy cable on towers across the valley where they had records of thousands of multiple strikes going back years.
And waited.
Nothing.
The cable (firmly grounded at the test end) never got hit. In fact, the lightning âwent awayâ. That which was intended to attract more lighting, actually caused the opposite effect. And they could not explain why.
I have also heard of the electrostatic energy potential above the earth, and agree about the high voltage present, and also minute current capability.
And as an amateur radio operator, I have held a fluro tube in my hand near the end of an antenna, and seen it light up in time with the transmission. No actual contact necessary.
Murray
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Hi Murray
Transmission monitor ??? Years ago at Belconnen (ACT) there used to be a Naval Transmitting station which had a VLF 200kW TX at about 40kHz. Over the years of course houses were built around this facility. In a lot of these houses fluorescent lights could not be used as they could not be turned off. This TX was mainly CW and the house lights would blink away in step with the morse transmissions. Most annoying.
Probably as I described above, the clouds or air mass discharged before lightning could strike.
Re lightning studies.
Mt Canobolas at Orange NSW is a known heavy lightning area. Many years ago I was doing some work on the ABC (Ch 0) TV antenna and I noticed a rather clever set up placed by one of the universities or CSIRO. A TV tower has 4 lightning spikes at the top, one in each corner. Each of these connect to a large copper cable running down inside each tower leg. This is then bolted to a galvanised bar which disappears into the ground connecting with the âTechnical Earthâ (separate and far superior than the âmainsâ earth).
Around this bar was placed a pick up coil of many turns to monitor the current in lightning strikes. This then presented a voltage version of the current waveform to a Techtronics oscilloscope (yes with a CRT and lots of valves) set up to trigger a single sweep at every lightning strike. A film camera was mounted on the front of this CRO with the shutter permanently open. The procedure was that a strike triggered the CRO and the resulting trace recorded on the film frame, then a motorised apparatus moved the film on one frame and waited for the next strike when the process was repeated. This whole set up was unmanned and periodically someone came and changed the film roll. All this and not a computer or processor in sight. No PCs, Digital Cameras and all those nice things in those days (1960s).
Cheers Bob
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A Techtronix 585 by chance?
Hi Gerard
Too long ago to remember now. But it was one of those large boxes with a big long CRT and all valves (tubes in USAese). Was smart enough to be able to trigger a single sweep every time lightning sent current down that earth strap. And like most Tektronix instruments of the tome had a camera mount for the front all sealed up so the shutter could be left open. I remember using special Polaroid cameras for taking CRO pics in different situations.
Beutifully built instruments. Even had a roll of special silver impregnated solder to facilitate repairs and component replacement inside the case.
Cheers Bob
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Yeah I reckon it was a 585. We had them at Control Data Corporation. It was a beautiful piece of kit.
Later, we migrated to the Techtronix 465 scope. Again, a great and reliable scope.
Hi Gerard
Tek had a mile of different models in those days. When I was working we had probably 6 or 7 different types, some with a selection of plug in modules for front end and time base. Some were leaning toward TV use and one I remember had an extremely fast (for its day) time base which was used for TV studio video timing where this was done by adjusting cable lengths.
Cheers Bob
Oh yeah! I remember the plug-in modules now that you mention it. Adjusting cable lengths was also something we did to tweak the timings in mainframe computers. 0.7nsec per foot, if my memory serves.
Hi Gerard
This has brought to mind a conversation we had in another post recently about removing the mains earth on the instrument. With TV the mains earth will introduce faults which are really not there as there usually quite a few volts between the âmainsâ earth and the âtechnicalâ earth. These scopes (particularly the TV ones) had a facility to do that easily. You simply unplugged the mains cable from the back and reinserted it upside down, job done.
Cheers Bob
All the kit we worked on was US voltages 115V single phase, 208V 3 phase. Most of the US style 115 plugs had the earth wire exposed so you could isolate the earth by unscrewing the earth wire from the earth pin. As a callow youth, I got zapped on more than one occasion with floating earths!
Curiously, the main mainframe power was 3 phase 400Hz since the original CDC engineers were ex-US Navy where 400Hz shipâs power was common. Of course, this meant that we used 125kVA 50Hz generators to drive the 400Hz alternator.
