Preselector And L.o - Swann CUBIC ASTRO 102 BX Service Manual

preselector board and connect
switch to CW, and MIC GAIN
Adjust the oscilloscope for
eCUBIC
COMMUNICATIONS
5"".",
DIVISION
PRESELECTOR AND L.O. BANDPASS FILTER ADJUSTMENT
The alignment of the bandpass filters should
be
performed only if abso-
lutely necessary, and then only for those bands that require alignroent.--rn-
dications of misalignment are significant reduction in power output and re-
ceiver sensitivity that is not the result of a component failure or-mis-
alignment of transformers, coils andjor oscillators on the exciter board.
If alignment is to be performed using a sweep generator, follow the
procedure supplied with the test equipment and test the boards as follows:
Preselector Bandpass Filters: (with sweeper)
Connect the sweep generator output to the RX IN jack (J132) and the
s~
ectrum analyzerOs input to the RX OUT jack (J136). Sweep each band according
to the accompanying chart.
L.O. Bandpass Filters: (with sweeper)
Disconneet the leg of C177 from pin 7 of ZlOl on the LO board and con-
nect the sweep generator output to the leg of C177. . Connect the analyzer
input to the LO OUT jack (JIO)).
Sweep each band according to the accompanying chart.
Preselector Bandpass Filters: (without sweeper)
Disconnect the TX OUT coax at J134 on the
the oscilliscope probe to
J~)4.
Set the MODE
control to fully clockwise, and key the unit.
areasonabIe indication.
Adjust the bandpass coils for maximum indication on the oscilloscope at
the center frequency of each band.
Tune the PTO across each band and readjust the bandpass coils as neces-
sary to obtain a flat response (± 2 dB) across the band without significant-
ly reducing the maximJlm output.
1.0. Bandpass Filters: (without sweeper)
Disconnect the LO OUT coax at JIO) on the 10 board and conneet the osc-
illiscope probe to JIO). Use the same procedure for adjusting these band-
pass coils as in the preceeding section.
NOTE: It is not necessary to key the unit for LO bandpass filter
adjustment.
PRESELECTOR BANDPASS FILTER ALIGNMENT TABLE
BAND
RANGE. MHZ
CENTER FREQ.
COILS
160
1. S-2. 0
1.9
TlOl, Tl02, TlO)
SO
).5-4.0 3.750
Tl04, TlOS, Tl06
40
7.0-7.5
7.250
TlO?
TlOS, Tl09
20
14.0-21. 5
14.250
TlIO, Tlll, Tl12
15
21.0-11.5
21.250
Tll), Tl14, Tl15
10A, B, C, D 2S.0-30.0
29.0
Tl16. Tl17, TllS
S-12