Assembly Instructions Chapter 4

4-6 kW UHF Translator Chapter 4, Circuit Descriptions
837B, Rev. 0 4-4
VCXO Channel Oscillator Assembly
(1145-1206), which contains the VCXO
Channel Oscillator Board (1145-1204),
is used in place of the standard
Channel Oscillator Assembly, and an
AFC voltage from the PLL circuit
maintains the frequency of the VCXO.
4.1.6 (A5-A1) x8 Multiplier Board
(1227-1002), x2 Multiplier Board
(1227-1524) or x4 Multiplier Board
(1227-1525) ; Appendix D)
The output of the Channel Oscillator is
connected to the (A5-A1) the x8
Multiplier Board (1227-1002) for UHF,
the x4 Multiplier Board (1227-1525) for
VHF HB or the x2 Multiplier Board
(1227-1524) for VHF LB, which is
located in (A5) the Multiplier Enclosure
(1265-1125). The proper multiplier
board takes the output of the Channel
Oscillator (+3 dBm) and multiplies it
eight, four or two times by a series of
three, two or one x2 Broadband
Doublers (2x2x2 = x8), which produces
the L.O. signal on the desired
frequency needed for the upconversion
process. The signal is then amplified to
the +16 dBm level. A sample of the
multiplied L.O. Signal is fed to a
detector circuit which lights the Green
LED DS1 that indicates that the L.O. is
present at the Output Jack J2 of the
Multiplier Board. This Green LED is
seen through a hole the lid of the
Multiplier Assembly and is an
indication, when lit, that there is a
signal present at the output of the
Multiplier Board.
4.1.7 (A6) L.O. Filter, UHF (1007-
1101), VHF L.B. (1034-1211) or
VHF H.B. (2065-1000) ; Appendix
D)
The L.O. signal is filtered in (A6) a L.O.
Filter 1007-1101 UHF, 2065-1000 VHF
HB or 1034-1211 VHF LB) and then
sent (+15 dBm) to J2 on (A10-A1) the
Downconverter Amplifier Board.
The L.O. Input to the Downconverter
Amplifier Board is connected thru a 3
dB matching pad to the "L" Input of the
Mixer (Z1) at a +12 dBm level.
Combined IF Signal Path
The L.O. and the RF signals are mixed
in the Mixer Stage of the
Downconverter Amplifier Board to
produce the desired IF difference
frequency at -55 dBm to -10 dBm in
level, depending on the RF Input Level.
4.1.8 (A11-A1) IF Filter/ALC Board
(1227-1504) ; Appendix D)
The Combined IF Signal is routed to
(A11-A1) the IF Filter/ALC Board
(1227-1504), which is mounted in
(A11) the IF Filter/ALC Enclosure
(1265-1105). The IF Filter/ALC Board
contains a Pin Diode Attenuator circuit
which is part of the Automatic Level
Control (ALC) that controls the level of
the IF Signal to the two stage amplifier
ICs U1 and U2.
4.1.9 (A11-A2) (Optional) SAW
Filter/Amplifier Board (1035-1211)
; Appendix D)
The (Optional) (A11-A2) SAW
Filter/Amplifier Board (1035-1211) is
also contained in the IF Filter/ALC
Enclosure. The SAW Filter/Amplifier
Board connects to J5 and J6 of the IF
Filter/ALC Board if more attenuation of
the Out Of Band products is needed. If
the SAW Filter/Amplifier Board is not
needed, a jumper connects the
Combined IF from J5 to J6 on the IF
Filter/ALC Board.
The Combined IF is then bandpass
filtered to the needed 6 MHz IF
bandwidth around the 41.25 MHz +
45.75 MHz Combined IF signal and
amplified by U3 to the -41 dBm to +4
dBm Level before it is split. One output
is detected by U4 for use as the ALC
reference level to the Pin Diode
Attenuator Circuit. The ALC