ACCEPTANCE TESTING
6-18
Internal FM deviation
Specification
Range:
1 MHz max for frequencies up to 21.09375 MHz.
Up to 1% of carrier frequency for carrier frequencies above
21.09375 MHz.
Resolution:
3 digits.
Accuracy:
±
5% of indication
±
10 Hz at 1 kHz rate internal modulation source.
Distortion:
Less than 3% at maximum deviation for modulation frequencies up to
20 kHz.
Test equipment
Description Minimum
specification Example
Modulation meter
Minimum frequency 20 MHz
Aeroflex 2305
+ distortion option
Test procedures
(1) Connect the test equipment as shown in Fig. 6-9.
(2) Set the UUT to
[Carrier Freq.]
21 MHz
[RF Level]
0 dBm
[FM Devn.]
210 kHz. Measure
the FM deviation on the modulation meter.
(3) Set up a carrier frequency step on the UUT of 1 MHz as follows:
[
Δ
]
[Set Steps] [Carrier Step]
1 MHz [SIG GEN]
(4) Set up an FM deviation of 500 kHz and increment the carrier frequency up to 42 MHz using
the '
×
' key, measuring the deviation and distortion on the modulation meter at each step.
(Note that the deviation will automatically be limited to 1% of the carrier frequency for each
step.) Check that the measured deviations are within specification.
FM attenuator
(1) With the test equipment connected as in Fig. 6-9, set the UUT to
[Carrier Freq.]
31.64 MHz
[RF Level]
0dBm
[FM Devn.]
1,260 Hz.
(2) Measure the FM on the modulation meter at the deviations indicated in Table 6-13. Check
that the measured deviations are within specification.
Table 6-13 FM attenuator deviations
Deviation (kHz)
1.26 79
224
20 159
316