500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page
4-4
15 January 2005
Table 4-1 Preliminary Switch Settings
NOMENCLATURE REF INITIAL
TEST OPERATING
USED IN TEXT
DES
SETTING
SETTING
SETTING
SPEAKER
A10S3
OFF OFF OFF
MONITOR
A1S4
BYPASS
BYPASS
NORMAL
TEST-Volts/Current
A1S5
OFF OFF OFF
SELECT MAIN TX
A1S3
A
A
A
or
B
RF
A1S1
OFF
OFF
ON
TEST-Power/Mod
A1S6
OFF OFF OFF
CONTROL
A1S2
LOCAL
LOCAL
LOCAL
or
REMOTE
KEYING
A4S1
OFF
OFF
ON
KEYING
A5S1
OFF
OFF
ON
MOD
A4S2
OFF
OFF
ON
MOD
A5S2
OFF
OFF
ON
POWER-AC
LINE
A6S1
OFF
ON
ON
POWER-BATTERY
A6S2
OFF
OFF
ON
POWER-AC
LINE
A7S1
OFF
ON
ON
POWER AC LINE
A8S1
OFF
ON
ON
RF
MON
A9A2S1
VOL
or
CUR
As Determined
As Determined
Side 'A' Status
A10S2
NORMAL NORMAL NORMAL
Side 'B' Status
A10S1
NORMAL NORMAL NORMAL
MODULATION PERCENTAGE INDICATION
4.8
Current and voltage transformers in the
forward/reflected power probe, which is in the output
of
harmonic filter A9
, provide samples that are
representative of the RF output current and voltage
waveforms. When the transmitter's RF output is
being applied to a precision, 50-ohm, resistive dummy
load and the load impedance is precisely 50 ohms at
the carrier and sideband frequencies, the waveforms
provided by both transformers will be identical.
When the transmitter's RF output is being applied to
an antenna system, the sideband impedance will be
high or lower than 50 ohms. If the sideband
impedance is less than 50 ohms, the current
transformer's waveform is selected as the source for
the RF monitor sample. If the sideband impedance is
greater than 50 ohms, the voltage transformer's
waveform is selected as the source for the RF monitor
sample. The RF monitor sample is applied to the
RF
MONITOR
connector for external monitoring and to a
modulation detector circuit. The output of the
modulation detector circuit is displayed on the
TEST-
Power/Mod
meter as a modulation percentage
indication.
