Nautel XR3-PREINST, Руководство по предварительной установке

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XR6/XR3 Pre-installation Manual RF output requirements
Issue 3.0 2009-07-15 Page 8-1
Section 8: RF output requirements
This section describes requirements associated with the antenna and RF cabling to be used with the
XR6/XR3 transmitter.
Antenna considerations include the following:
• Antenna feed cable
• Antenna system - see page 8-3
For detailed information about protecting the transmitter system from antenna lightning strikes, see
the
Nautel Site Protection Manual .
Antenna feed cable
Maximum voltage
The maximum voltage at the transmitter’s connection to a 50
Ω
load is 2,617 V peak, when operating
at 6 kW (1,851 V peak at 3 kW), with 125% modulation.
High voltage feed throughs
Be very careful whenever a high voltage RF conductor passes through a wall or bulkhead. Gas
insulation flashovers can occur in poor installations. Ensure that this part of your installation is
installed by professionals experienced with high-power radio frequency circuits.
Insulator flashover.
Surface flashovers along an insulator occur when there is an electrical
breakdown in the gas (normally air) at its surface. The mechanism that triggers a flashover depends
on the insulation surface conditions. Gas breakdown flashover occurs when one or more of the
following conditions are met:
• The voltage field at the insulator surface or at an adjacent electrode reaches the critical break-
down level for the gas.
• The electrode or insulator interface is poor or dirty, resulting in a three material junction.
This creates excessive high voltage stress on the air insulator, causing a gas breakdown flash-
over.
• Moisture damage on the insulator surface creates regions of high voltage that can cause a gas
breakdown flashover.