Nautel NX3, Installation Manual

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NX5/NX3 INSTALLATION MANUAL ADJUSTING THE SPARK GAP
VERSION 3.1 2021-04-22 PAGE 2.5.1
SECTION 2.5: ADJUSTING THE SPARK GAP
The NX5/NX3’s RF output filter contains a spark gap that must be adjusted - based on site altitude - to
provide protection against excessive voltage (i.e., lightning) on the RF output.
NOTE:
Nautel presets the spark gap for 0.022 inches, which corresponds to a site altitude of 0 m (i.e.,
sea level). If your transmitter site is at sea level, no spark gap adjustment is required.
1. Determine the altitude of the transmitter site (in feet).
2. Make sure that the ac power is switched off and locked out.
3. Gain access to the RF output spark gap by opening the front door and then opening the hinged
exciter panel, noting it is secured using 16 M5 screws. Retain hardware.
4. Locate the spark gap (see Figure 2.5.1 on page 2.5.2 ). Using a feeler gauge, measure the air gap
between the spark gap balls.
5. The air gap should be 0.022 inches multiplied by the scale factor listed in Table 2.5.1, “Altitude
Scale Factor” on page 2.5.3 for the altitude determined in Step 1 . If not, loosen the locking nut on
the bottom carbon hemisphere, adjust the position of the spark gap ball for the required gap and
then tighten the locking nut.
6. Close and secure the exciter panel using the M5 screws retained in Step 3 .
WARNING! THE AC VOLTAGES PRESENT IN THE TRANSMITTER CAN BE
FATAL. EXERCISE EXTREME CAUTION.