Operating instructions

OPERATING MANUAL 2945A
46882-311D 5-23
Splitter
Signal generator
C2592
RF INPUT
ANTENNA
INPUT
RF OUTPUT
Modulation meter
UUT
Fig. 5-16 Modulation analyzer - AM
(1) Refer to Results table 5-36 on page 5-42. Connect the equipment as shown in Fig. 5-16,
connecting the incoming signal to the antenna input socket of the UUT.
(2) Set the Modulation meter to monitor AM in a 50 Hz to 15 kHz bandwidth, Noise averaging
on.
(3) Set the UUT to [Tx TEST], RF IN/OUT [SELECT] antenna input socket, [Mod Meter].
Press the [AM/FM] soft key to set the UUT to demodulate AM. From the power up default,
the instrument should already have an IF filter of 30 kHz and AF filter of 0.3 to 3.4 kHz
selected. Check that this is the case and select if necessary.
(4) Tune the UUT to 500 kHz by pressing [Return], [Tx Freq] 500 kHz. Set the RF signal
generator to provide a signal of 500 kHz with 70% AM at 1 kHz modulation rate. Set the RF
level to 6 dBm. (If a 2041 is being used, it should be set to normal noise mode.)
(5) Check that the AM depth indicated on the UUT is within
±
5% of reading
±
1 digit of the
depth indicated on the external Modulation meter.
(6) Repeat steps 4 and 5 for RF carrier frequencies of 500 MHz and 1050 MHz.
(7) Refer to Results table 5-37 on page 5-42. On the UUT, select the 300 Hz low-pass filter and
TX FREQ 100 MHz.
(8) Set the external modulation monitor bandwidth to 30 Hz to 50 kHz.
(9) Set the RF signal generator to provide a signal of 100 MHz with 70% depth at 50 Hz
modulation rate. Check that the modulation depth indicated on the UUT is within
±
8.5% of
reading
±
1 digit of the depth indicated on the Modulation meter.
(10) On the UUT select the 50 kHz low-pass AF filter and the 300 kHz IF filter. Change the
modulation rate on the RF signal generator to 10 kHz and check that the modulation depth
indicated on the UUT is within
±
8.5% of reading
±
1 digit, of the depth indicated on the
Modulation meter.
(11) Refer to Results table 5-38 on page 5-43. When finished, select the 0.3 to 3.4 kHz filter on
both the UUT and the external Modulation meter. Select the 30 kHz IF filter on the UUT.
(12) Set the RF signal generator modulation rate to 1 kHz and set 5% AM depth.
(13) Check that the AM depth indicated on the UUT is within
±
5% of reading
±
1 digit of the
depth indicated on the Modulation meter. Repeat with the RF signal generator set to provide
depths of 20%, 50%, 80%, and 95%.