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Thanks to Dan TURKISHER |
DESCRIPTION
The "SURGE SHUNT" protects solid state communications equipment from high voltage transients, the most common being those induced by lightning strokes. It consists of a hermetically sealed "voltage dependent switch" housed in a unique package which allows insertion at any point in a coaxial feed line by means of a standard
T-connector supplied with the unit. The device’s low capacitance and the near constant impedance housing/T-connector combination allow the unit to be used at UHF with minimum insertion loss Other competing units are packaged using low frequency packaging techniques that precludes operation at UHF with acceptable insertion loss levels.The switch threshold of the "SURGE SHUNT" is a function of rise time, and varies from 230 volts up to 750 for extremely fast rise time transients. When the switch threshold is reached, an arc forms providing a low impedance shunt with voltage transients clamped to less than 30 volts.
INSTALLATION AND USE
The "SURGE SHUNT" can be installed at any convenient point in a coaxial
feed line. The VSWR should not exceed 2:1 and maximum RF power level should be
limited to 200 watts.
If a linear amplifier is used, the "SURGE SHUNT" should be placed between the
transmitter/transceiver and amplifier. This provides needed protection to
transmitter/transceiver while not violating the 200 watt max constraint. No protection
between the antenna and linear amplifier is generally needed, as most amplifiers are
tube-type and not susceptible to transient damage. In addition, protection at this point
in a system must necessarily be limited to the 750 volt to 1 KV protection level
which is generally much higher than that at which damage can occur, and therefore would
provide little if any protection.
The "SURGE SHUNT" itself provides a low impedance ground path that is
satisfactory. However, if the station ground is floating relative to earth ground or if
station ground is less than ideal, the stud on the "SURGE SHUNT" can be used to
connect station ground to a driven rod ground or cold water pipe ground. The "SURGE
SHUNT" integrates station ground and surge arrestor ground keeping with the fact that
there can only be one "real" ground.
If used outside, weather proof the connection between housing and T-connector with
electrical tape or a clear protective spray.
REPLACEMENT OF SURGE SHUNT ARRESTER
Although the replaceable arrester in the "SURGE SHUNT" can handle repeated arcing action, over a period of time multiple high energy transients can cause a gradual shift in the break down voltage. If this is indicated or suspected, a replacement arrester can be inserted in the "SURGE SHUNT" by removing it from the T-connecter and replacing the old arrester device with the new one. Replace housing on T-connector and tighten just until proper contact between arrester and device is evidenced by lack of slight. rattle when shaking T-connector/"SURGE SHUNT" assembly.
FREQUENCY:
Insertion loss less than 1 dB up to 400 MHz 1.5 dB max up to 500 MHz
ARC THRESHOLD
230 volts to 750 volts depending on transient rise time
