Table of Contents
Advertisement
I
' '
j~
!
~
'
....
-
The combined mark and space signal is derived through output
logic circuits and the low level keyers or the optional high
1 evel keyers.
4.3
DETAILED FUNCTIONAL ANALYSIS
The following detailed functional descriptions explain how the
equipment operates by following the signal through each circuit
and
explaining
each
operation.
Where
the
circuits
are
identical for input signals only one signal will be discussed.
Where identical circuits are utili zed f.or the mark and space
signals only the mark signal will be discussed.
4.3.1
Input Circuits
The input signal is applied from the rear panel through an
impedance matching switch (10K/600
ohm)
to the input circuit
board (reference Figure 4-2).
Here the signal is routed to the
input amplifier and AGC circuits.
The input amplifier is a
single stage of amplification which produces a 3-to-1 voltage
gain.
The AGC circuit consists of a voltage follower, which
produces a 100-to-1 AC gain, and a slow reacting peak detector
configured in a feedback loop.
this configuration produces a constant amplitude signal which
is applied to the multiplexer where it is routed to either one
or
both
of
the
demodulator
units.
The multiplexer
is
controlled by the front panel demodulator selection switches or
by the computer control unit.
The input signal is also applied throught the input amplifier
to the level detector circuits.
The level detector circuits
consist
of
two
operational
amplifiers which,
according
to
signal conditions, will activate either the >0 dBm line or the
>-20 dBm line (active state is a logic 0).
The detected level
is applied to multiplexers which routes the signal to selected
LEVEL indicators.
These signals will cause the corresponding
level
indicators to
illuminate,
HI level
indicator
if the
signal
is
>0 dBm,
NOR level
indicator
if the
signal
is
>-20 dBm.
If neither line is active the LOW indicator will
illuminate •
4.3.2
Demodulator Unit
Each demodulator unit consists of three printed circuit boards
the
synthesizer
board,
the
Bandpass Filter
board
and
the
Demodulator
board.
The
following
paragraphs
contain
the
detailed functional descriptions of each printed circuit board.
4-3
Advertisement
Table of Contents
