Aeroflex 2050T SERIES, Operating Manual, Page: 223 / 322

ACCEPTANCE TESTING
6-20
External FM
Specification
Accuracy: With ALC OFF the modulation is calibrated for an input level of 1.0 V
PD RMS sine wave.
±1 dB bandwidth:
DC to 300 kHz. Typically 500 kHz.
Test equipment
Description Minimum specification Example
Modulation meter Modulation frequencies from 30 Hz to 50 kHz. Aeroflex 2305
Function generator DC to 300 kHz sine wave. HP3325B
Frequency counter Up to 40 MHz. ETP 535B or
Aeroflex 2440
Test procedures
C0225
UUT
2440
Counter
Function Generator
A INPUT
50
Ω
Load
EXT MOD 1
INPUT
RF
OUTPUT
➤
➤
OUTPUT
! !
Fig. 6-11 External FM test set-up
(1) Connect the test equipment as shown in Fig. 6-10.
(2) Set the UUT to [Carrier Freq.] 35,468,750.1 Hz [RF Level] 0 dBm [FM Devn.] 40 kHz.
[UTIL] [Mod'n Mode] [Comp]
[SIG GEN] [Select Source] [Select External]
[Ext1 AC Coupling]
[SIG GEN] [FM2] [Select Source] [Ext2 AC Coupling]
[SIG GEN] 40 kHz [FM1] 40 kHz
The UUT will now produce FM when the external modulating source is applied to either
modulation input.
(3) Set the function generator to give 1 V RMS at 1 kHz sine wave.
(4) With the modulation meter set to measure FM, set a reference using the relative function.
(5) Set the function generator to the frequencies shown in Table 6-15 and measure the change in
external FM response which should be less than 1 dB with respect to 1 kHz.
(6) To measure the FM deviation at DC, it will be necessary to connect the test equipment as
shown in Fig. 6-11 and DC couple the EXT MOD 1 INPUT as follows:
[Select Source] [Ext1 DC Coupling] [SIG GEN]
(7) Using the DC offset facility on the function generator, set up a voltage of +1.4142 V
(i.e. 2).
(8) Measure and record the frequency indicated on the counter (F1).
(9) Set the function generator to give a DC voltage of -1.4142 V.
(10) Measure and record the frequency indicated on the counter (F2).