Frequently Asked Questions

Damage to Systems with SP-8 Installed

The SP-8 Heavy-Duty Surge Protector is a very effective protection system for the RFC-1/B. Field data indicates that it reduces lightning damage by about 98%.

Almost every case of lightning damage to systems using the SP-8 was caused by arc-over in the control relays. The insulation in the control relays between the contacts and the coil is effective to about 5000 volts. When the voltage rises above that, flash-over occur from the contacts to the coil.

High voltage flash-over introduces high voltage to the ICs on the relay panel, the line driver IC in the RFC-1/B and to the power supply. Sometimes only ICs are damaged. In more severe cases other components are damaged.

To prevent a recurrence of this problem, identify which control source is generating the high voltage transient and install varistors on the control leads to that device. In most cases, the source will be the transmitter. When a tower gets hit by lightning, the entire transmitter can be elevated above ground by hundreds or even thousands of volts.

Varistors installed on RP-8 control leads

The varistors should be installed near the RP-8 panel as shown in the diagram above. It is often convenient to solder one side of the varistors to a piece of large copper wire (#10 or #12) and connect both ends of this wire to the rack in which the RP-8 is mounted.