[TowerTalk] Lighting

[Tom Rauch]

> While visiting Chuck, WA1EKV and looking at his 100 Ft
tower on a hill with
> a comb of sharp points on top and 3 large ground leads at
the bottom, he
> told me that he once heard hissing from the top of the
tower during a time
> of dark clouds. He then measured the current in one of the
ground lines with
> a clip-on DC ammeter and found 100 Amps....implying a
sustained 300 Amps
> total bleeding from the cloud to ground.

I've measured current in my insulated base 318 foot tower
several times when it has been hissing, and the current was
in the milliamp range.

As a matter of fact, we used RF chokes made of #18 nichrome
wire to bleed AM BC towers to ground so LTU's didn't charge
up and arc, and never had a choke heat or fail from
lightning. If the corona current was anywhere  over a few
amperes, the chokes would have been toasters.

The stepped leaders at the start of a strike are estimated
at 150-200 amperes. 300 amperes is lightning strike current,
not corona current. Assuming 1 MegV of potential difference
the dissipation in the path would be 300MegW.

I'd recheck those currents!

73 Tom