Assembly Instructions Chapter 4

4-6 kW UHF Translator Chapter 4, Circuit Descriptions
837B, Rev. 0 4-30
4.2.15 (A15-A1) x8 Multiplier
Board (1227-1002; Appendix D)
The x8 multiplier board multiplies the
frequency of an RF input signal by a
factor of eight. The board is made up of
three identical x2 broadband frequency
doublers.
The input signal (+5 dBm) at the
fundamental frequency enters through
SMA jack J1 and is fed through a 3-dB
matching pad, consisting of R1, R2, and
R3, to amplifier IC U1. The output of
the amplifier stage is directed through
a bandpass filter, consisting of L2 and
C4, that is tuned to the fundamental
frequency (87 to 114 MHz). The
voltage measured at TP1 is typically
+.6 VDC.
The first doubler stage consists of Z1
with bandpass filter L3 and C6 tuned to
the second harmonic (174 to 228 MHz).
The harmonic is amplified by U2 and it
is again bandpass filtered at the
second-harmonic frequency by C10 and
L5 (174 to 228 MHz). The voltage
measured at TP2 is typically +1.2 VDC.
The next doubler stage consists of Z2
with bandpass filter C12 and L6 tuned
to the fourth harmonic of the
fundamental frequency (348 to 456
MHz). The fourth harmonic is then
amplified by U3 and fed through
another bandpass filter, consisting of
L11 and C18, that is tuned to the fourth
harmonic (348 to 456 MHz). The
voltage measured at TP3 is typically
+2.0 VDC.
The final doubler stage consists of Z3
with bandpass filter C20 and L12 tuned
to the eighth harmonic of the
fundamental frequency (696 to 912
MHz). The signal is amplified by U4,
U5, and U6 to a typical value of +2 to
+4 VDC as measured at test point TP4.
The amplified eighth harmonic is then
fed to J2, the SMA output jack of the
board. The typical LO signal output
level is +15 dBm nominal.
The detected sample of the output of
the x8 multiplier board at TP4 is also
fed to the base of Q1, which forward
biases it and lights the green LED DS1
on the board to indicate that the LO
signal is present.
The +12 VDC for the board enters
through jack J3-3 and is filtered by L7
and C16 before being distributed to the
circuits on the board.
4.2.16 (A12 and A16) UHF Filters
(1007-1101; Appendix D)
Each of the UHF filters is a tunable
two-section cavity filter that is
typically tuned for a bandwidth of 6
MHz and has a loss of -1 dB through
the filter.
4.2.17 (A11) UHF Upconverter
Board (1265-1310; Appendix D)
The UHF upconverter board provides
upconversion processing by mixing the
IF and LO signals in mixer Z1 to
produce the desired RF-frequency
output. The RF output is connected
through J3 to an external filter and
applied back to the board at J4 where
the gain is set by R10. The RF is
amplified and connected to the RF
output jack of the board at J5.
The IF signal (0 dBm) enters the board
at J1, an SMA connector, and is applied
through a filter circuit consisting of L10
and C25 to C28 and to a matching pad.
This pad consists of R1, R2, and R3,
which presents a relatively good source
impedance, and feeds the signal to pins
3 and 4, the I input of mixer Z1. The
local oscillator signal (+13 dBm) from
the x8 multiplier connects to the board
at jack J2, an SMA connector, through
a UHF channel filter and is connected
directly to pin 8, the L input of the
mixer.