[Elecraft] OT: Grounding Question

[Jim Brown]

Thanks for this reference.  K6STI sent me a comparable paper from NASA. 
Note that the graph (which came direct but not on the reflector) is for 
the radiated field, not the energy in the strike itself. My reference 
for lightning spectrum is for the energy in a strike, and is from IEEE 
Standards for power and grounding, which are published as "The Emerald 
Book" and "The Green Book."  It's been at least ten years since I read 
it, and I don't recall in which book it is stated.

73, Jim K9YC

On 4/25/2018 5:17 PM, Jef Allbright wrote:
> On Wed, Apr 25, 2018 at 4:17 PM, Jim Brown<jim at audiosystemsgroup.com 
> <mailto:jim at audiosystemsgroup.com>>wrote:
>
>     On 4/25/2018 1:59 PM, Jef Allbright wrote:
>
>         The vast majority of the energy in a lightning strike is well
>         below 1 MHz
>
>     WRONG! Lightning is a VERY short rise-time impulse, so it is an RF
>     event, not a DC event.
>
>
>
> Jim -
>
> The energy from a lightning strike typically can be detected up to 
> about 20 MHz but as you can see from Willett, 1990, the energy curve 
> diminishes and /*is already down about -25dB before it reaches 1 
> MHz*/. So the bulk of the energy is released well below 1 MHz.  To 
> provide equivalent energy above 1 MHz, you'd have to imagine the graph 
> somehow suddenly leveling off and then continuing at that amplitude 
> (25dB down) for nearly 500 MHz to provide a similar integral area.