At 08:40 AM 2/25/2005, dgsvetan@rockwellcollins.com wrote:
>John and Bud,
>
>It may be counter-intuitive, but it is explanable. Briefly, there are
>gradient fields produced whenever/wherever lightning strikes.
>That helps a lot, but still leaves them subject to gradient field
>energy unless they are buried deeply or in metal conduits. (The usual
>burial medium these days seems to be plastic tubing or pipe, not metal).
>
>Hope this explanation helps.
Dale--
I appreciate the detailed EM-theory explanation. My phone line is buried
for 30 miles except for an above-ground section to cross the road so
that it can come onto my property and then is underground for the last
600 ft to the house.
When I was the engineer for the University of Colorado's Radio Astronomy
Observatory in the 1970s our power lines and our phone lines were buried
for a number of miles before coming into the steel building. We were always
worried about lightning because we did HF and low VHF radio astronomy
and had a lot of wire antennas covering many, many acres. But ALL of
our problems were spikes that came in on the phone and power lines.
Don't recall ever fixing an antenna preamp failure due to lightning.
We solved our problem with our cesium and rubidium clocks getting
toasted every time there was a lightning storm by running them
from a constant-voltage transformer. Being ferro-resonate (tuned
circuit) it would not pass the sharp spikes from the lightning.
Lightning was a constant and serious consideration at our 8,800 ft elevation
site in the Rocky Mountains. One of the techs told the story about
the lightning storm where he just sat in the middle of the floor waiting
for the lightning to stop. There was a little metal coat rack by the
door (inside the metal building) and he was even getting corona off
the tips of the coat hanger hooks during that storm! Truly SCARY!!
73--John W0UN
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|