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blowing across the antenna, precipitation hitting the active element, or other environmental causes. As static charge
builds up on the antenna's active element, over a period of minutes or even hours, the DC blocking capacitor inside the
lightning arrestor is charged.
Figure 8 Voltage buildup due to static
When the voltage exceeds 600V (the breakdown voltage for IS-B50LN series PolyPhasers), the gas discharge tube turns
on and the antenna side of the DC blocking capacitor is immediately pulled from 600V to 0V. Since the lighting
arrestor's capacitor was charged to 600V, that charge must dissipate through the radio. As the capacitor discharges, a
large negative transient is created on the antenna port of the radio. Positive transients can also be created if the static
charge buildup on the antenna has a negative polarity.
Figure 9 Voltage Transient immediately after the gas tube turns on
During testing, transients were measured on the antenna port of CalAmp's Viper at voltage levels up to +/-280V. These
voltage transients often have high frequency content that can easily pass through any filtering in the radio and damage
components in the transmitter and receiver circuitry.
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Guardian™ Serial Modem or Analog Radio for Licensed Spectrum PN 001-5006-000 Rev. 3
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