... edited by Barry Mishkind - the Eclectic Engineer
The Worst I’ve Ever Seen!
Fun With A Real Flamethrower
[October
2011]
You have to
love it. Broadcasting with the big transmitters can definitely
present the occasional bang - or worse. No wonder we call them
"flamethrowers!"
Here is
something that happened as
part of the growing pains that can occur when diplexing a
pair of 50 kW signals into a directional array. Andy Skotdal
of KRKO/KKXA kindly shared this video of what they found on
one site, and explained what they did to solve the problem.
As you can
imagine, it is not an easy task when you are tossing 100 kW
around. Not only are there all sorts
of networks, both matching and filtering to get "just right," there were six
towers where the problems could originate.
At first they knew only that they had an arc somewhere in
the transmission system. Then they found it, perhaps aided by
the pungent ozone smell.
As they said on site: "Are
you ready?" OK ... click on the video.
Video Courtesy of KRKO
The engineers
from Hatfield and Dawson were on site and solved this
particular arc. Among the steps they suggested to eliminate
the problem:
1. Use
wider strap but eliminate the excess attached to the tap.
2. Add corona rings to the dead ends of the coil.
3. Strip the paint from the outer edge of the door and box
frame.
4. Add copper trim around the door.
5. Ground the door.
6. Bolt the door permanently shut.
7. Retune after modifications.
... and hope
for no more arcs anywhere on the site of the 100 kW
transmission plant!