[BC] More thoughts about AM transmitter lightning

[Gary Peterson]

" Sometimes it's also necessary to put 100 k resistors across the guy
insulators
to keep static build up down...
Dana  Puopolo "

I had a 5 kW daytime, ND site that suffered from severe transmitter hiccups
(Collins 828E-1 Power Rock) when a thunderstorm was building.  The humidity
is very low here and, before it starts to rain, the potential gradient in
the air becomes very high.  The cause of the hiccups appeared to be due to
the guy wire insulators (johnny balls) all flashing over, simultaneously.
At that instant, there is a brief, low impedance path from the tower to the
guy anchor (ground).  During a building storm, the insulator flashovers
sounded like popping popcorn (quite a site at night) and the transmitter
would recycle several times a minute.

In the late 1980s, a decision was made to go full time with a two tower DA.
Because there was not enough real estate available at the existing site, a
new site was constructed about 3/4 mile away.  On both of the new towers, I
specified long insulators where the guys attached to the tower, where the
guys attached to the anchors and at the midway point of the upper two sets
of guys.  These insulators are several feet long and appear to be something
like fiberglass rods.  I have seen these used by the power industry.  In
between the long insulators, the guys were broken up with the usual johnny
balls.

The new site has been in use for nearly twenty years and I have only heard
the transmitter hiccup once during a storm and that was probably due to a
direct or nearly direct strike.  No popping noises have ever been heard at
the new site.  The sheer length of the insulators prevents the guy insulator
arcing problem.  Since that time, I have added long insulators to the guys
at two other AM sites in the area, with similar success.

Gary, KØCX
CE KFXS, KOUT, KKMK, KRCS, KKLS & KBHB
Schurz Communications, Inc.
Rapid City & Sturgis, SD