Operating instructions

ACCEPTANCE TESTING
5-10
(7) To confirm the low residual FM of the UUT, the use of an extremely low-noise FM
demodulator is necessary; this is achieved by using the IFR 2041 Low-noise signal generator
as the local oscillator for the 2305. Connect the test equipment as shown in Fig. 5-6
(8) Refer to Results table 5-8 on page 5-34. Set the UUT to [Rx TEST], RF IN/OUT [SELECT]
B
NC output, [RF Gen], [LEVEL] 0 dBm, [ FREQ], 1000 MHz. Switch all modulation
generators and noise measurements off.
(9) Set the signal generator into low noise mode 1 and to provide a signal of 55.63889 MHz at
0 dBm.
(10) Set the Modulation meter to measure FM in a 300 Hz to 3.4 kHz bandwidth with noise
averaging on. Select external LO by pressing FREQ TUNE, 0, ENTER. External LO should
now appear in the top left of the modulation window display and the frequency window
should display the IF frequency of 1.5 MHz ±150 kHz. Check that the residual FM
displayed in the modulation window is less than 12 Hz.
(11) Set the UUT RF Generator and the local oscillator to the frequencies shown in Results tab
le
5-8, confi
rming that the residual FM indicated on the Modulation meter is within the limits
shown in the right hand column.
(12) MHz can be measured with the 2305 in its normal mode of operation; e.g. press [Auto Tune]
to switch off the external LO mode.
UUT
Signal generator
C2586
RF INPUT
BNC
OUTPUT
RF OUTPUT
EXT LO
INPUT
Modulation meter
Fig. 5-6 Residual FM checks