Print Date 08/04/14 Page 22 of 34 S79005-00MA-05
8) Set the E2026 Drive Changeover/Output Monitor front panel switches to START and SELECT
A or SELECT B to connect an Exciter/Drive to the Transmitter itself.
9) Set the E2026 Drive Changeover/Output Monitor Unit’s front panel HIGH POWER and LOW
POWER twenty turn controls to fully clockwise (i.e. maximum power setting). Ensure that the
HIGH POWER control display is on. If the LOW POWER display is on, check that the link LK1
FORCE LOW POWER on the rear left hand side Bus Board is removed (just above the Power
Supply Unit).
10) Slowly increase the selected Exciter/Drive(s) output power until 500W is just obtained. To
ensure complete accuracy, an external calibrated power meter should be used to measure
this output power. Increase the input level by a further 1dB (approximately 20%). In no case
however must the input power exceed 13W. The output power should rise above 500W.
11) If a second Exciter/Drive is fitted, repeat step (10) with the E2026 front panel switch set at
SELECT A or SELECT B to connect it to the Transmitter itself.
12) With the Exciter/Drive power set as described, turn the HIGH POWER control anti-clockwise
until the measured output power falls back to 500W (or less if required). Check the same
power is obtained by selecting the other Exciter/Drive if fitted (using the E2026 front panel
switch).
13) Link LK1 FORCE LO POWER on the rear left hand side Bus Board The LOW POWER display
on the E2026 should come on in place of the HIGH POWER display.
14) With the Exciter/Drive power still set as described, turn the LOW POWER control anti-
clockwise until the output power falls back to the level required, typically down to
approximately half of the Transmitter’s maximum rated output. Check the same lower power is
obtained by selecting the other Exciter/Drive if fitted (again using the E2026 front panel
switch).
15) Unless required to stay in low power operation, remove enable LK1 FORCE LO POWER.
16) Check that the output power displayed on the E2023 Control Unit also reads the set output
power. This reading will not be as accurate as the external calibrated power meter but should
be within about
±
0.25dB (approx. 25W at 500W).
17) If the reading is not within this range it may be adjusted by a preset control inside the E2026
Drive Changeover/Output Monitor Unit. To access this control, slide the E2026 forwards after
removing its two front fixing screws, taking care not to strain any leads connected to its rear.
The preset control (marked ‘CAL FWD’) is at the rear left hand side of the printed circuit board
accessible through an aperture in the screen cover. Care must be taken that none of the other
four preset controls on the board are altered. Adjust the control clockwise to increase reading
or anti-clockwise to decrease reading.
The Transmitter will now be ready for operation with audio and or data sources applied to the
Exciter/Drive(s). The manuals for the type of Exciter/Drive(s) supplied or in use must be again
consulted for information on how such sources are applied and controlled.
The RF Monitor connector at the left-hand front of the E2026 Drive Changeover/Output Monitor Unit
may be used to check the close-in spectrum of the Transmitter output signal. Note that any harmonic
levels shown will not necessarily indicate those present at the Transmitter output. Any test equipment
should not however normally be left connected.
2.3.3 Reverse Power Trip Level Adjustment
If the REV led on the E2026 Drive Changeover/Output Monitor Unit is intermittently or permanently
red, this indicates that the level of reverse power is greater than about 13W. This shows that the
antenna system connected to the Transmitter is relatively poor. If the Transmitter’s reverse power trip
point is set too low, this may cause a reduction in the available output power. As long as the E2021
Amplifiers’ REV leds are not also red, the trip point setting can be increased to help maintain full
output power (although the REV warning may still be displayed).
