Section V Models 78100A, 78101A
Maintenance
load during all power measurements (mW and dB). The 3. Adjust R55 to no more than 6.5 mA as indicated on
10 dB attenuation will affect mW measurements by a the transmitter external Power Supply meter. If spurious
simple scale change on the 432A Power Meter. Keep this in frequencies are generated other than the harmonics of the
mind in Paragraphs 5-48e (step 7), and 5-70. Other tests are crystal oscillator, disregard these frequencies for the
relative and are not affected. moment.
b. Set test box attenuator to 0 dB.
4. Readjust C25, C28, C30, C3 1, and C33 to maximize
the carrier output (Figure 5-15, with the amplitude of all
c. Apply dc power to transmitter (approx. 8V dc) with
other harmonics at least 23 db below that of the main
6234A DC Power Supply, OR, install battery and connect
multimeter in series to measure current. carrier i.e., 4th harmonic). The 2nd harmonic must be
greater than 30 db down from the main carrier (4th har-
d. Connect the RF output of the test box to 8554L monic). At this point, spurious frequencies may or may not
still be observed.
Spectrum Analyzer RF Section, RF Input connector
(Figure 5-13).
e. On transmitter, referring to Figure 5-14 for adjustment 5. Tune C33 through its entire range (360 degrees of
locations, rotation). In doing so, if spurious frequencies are generated,
retune C30 slightly to eliminate them. Now retune C33 for
1. Rotate R55 fully CW. maximum output of carrier relative to its harmonics. Note:
It may be necessary to perform this step more than once.
2. Adjust C25, C28, C30, C31 and C33 to maximize Refer to Figure 5-1 5 for typical spectrum analyzer presen-
the 4th harmonic. tation of carrier output.
COUNTER MULTIMETER
0 0
781 OOA
TRANSMITTER
I) C POWERMETER
007a0-63030
TEST BOX with 3
TRANSMITTER
3
r SPECTRUM
ANALYZER
-
8901 A
c MODULATION
ANALYZER
L
Figure 5- 13. Test Setup for Transmitter Tests
5-20 078 100-2 |
ACEC
