Harris Maxiva ULX COFDM Series, Technical Manual

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10/6/10 888-2629-200 D-3
WARNING: Disconnect primary power prior to servicing.
Maxiva ULX COFDM Series
Lightning from cloud to cloud produces horizontally polarized waves while lightning
from cloud to earth produce vertically polarized waves. The waves couple into the
power lines and transmission lines causing large induced voltage that destroy high
voltage rectifier stacks and output circuit faults. High frequency energy is coupled
back into the transmitter causing VSWR overloads, See Figures D-4 and D-5.
Remedy - Ball or horn gaps at the base of the antenna prevent the voltage from ex-
ceeding some high potential. Transient suppressor devices on the input power lines
remove excessive voltage spikes. Buried power and transmission lines will reduce the
amount of coupled energy to a great extent. This does not totally eliminate the prob-
lem because there are currents traveling in the earth, which prefer to travel on the
metal conductors, when lightning strikes close to the station.
5.
Surge. A rapid increase in voltage on the power lines usually caused by lightning. The
duration is less than 1/2 cycle and can be very destructive.
Remedy - Transient protectors are very effective in preventing damage to the equip-
ment when properly designed and installed, See Figure D-6.
Table D-1 Significant Lightning Stroke Characteristic
Charge Range 2 to 200 coulombs
Peak Currents 2,000 to 400,000 Amperes
Rise Time to 90% 300 Nanoseconds to 10
Microseconds
Duration to 50% 100 Microseconds to 10 Milliseconds
Potential Energy at
99% 1010 Joules*
* Only a small portion is manifested in a surge, usually less than
10,000 Joules.