E.F. Johnson Company VIKING VX, Руководство пользователя

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CIRCUIT DESCRIPTION
6-35
August 2000
Part No. 001-2001-200
latch U107. When enabled, the gate passes the voice
to Transmit Option Gate U158C and on to the transmit
audio buffer U164B. Transmit Voice amplifier U130B
is adjusted by a level control. The output is fed to
Transmit Net Gate U153B. Gate U153B is controlled
by A/D processor U111/latch U155.
6.10.11 TRANSMIT DATA AND CWID PRO-
CESSING
The data signal is produced by A/D processor
U111 on Transmit Data and Transmit Shape outputs.
The transmit shape output is normally the opposite
logic level of the transmit data output when data is
transmitted. However, the bit before a logic transition
occurs, the transmit shape output is the same logic
level as the transmit data output. This results in a
logic 1 level that is slightly higher and a logic 0 that is
slightly lower. This pulse shaping minimizes interfer-
ence between data bits when the data is filtered by the
low-pass filter.
The data from U111 is fed to buffer U126A and
Transmit Data Enable Gate U117B. Gate U117B is
controlled by A/D processor U111 directly. When
enabled this gate passes the data to EEPOT U151.
U151 is an electronically adjustable potentiometer that
adjusts the gain of transmit audio amplifier U126B.
The gain of U126B can only be adjusted through the
software. Therefore, a computer must be attached to
the MAC card. U126B provides the required signal
level at the output of the low-pass filter. A relatively
stable DC bias voltage for U126C/D is required
because these stages are DC coupled to the transmit
TCXO (see Section 6.2.3) and changes in bias voltage
can cause fluctuations in the transmit frequency.
U126C/D form a low-pass filter that attenuates
square-wave harmonics in the data signal above 150
Hz to prevent interference with the audio band. From
this filter the signal is fed to summing amplifier
U129B and combined with the transmit audio signal.
The output of U129B is fed to Transmit Modulation
Mute Gate U118D. This gate is controlled by A/D
processor U111/latch U106. When enabled, transmit
audio and data are passed to the Exciter modulation
input and the transmit TCXO.
When needed the External Modulation input on
P100, pin 11 is fed to External Modulation Mute Gate
U118C. Gate U118C is controlled by A/D processor
U111/latch U106. When enabled, this gate passes the
modulation on pin 11 to the summing amplifier
U129B and gate U118D to the modulation input of the
Exciter.
The repeater on the lowest frequency channel in
each system must periodically transmit the station call
letters as a continuous-wave identification encoded by
Morse Code. This identification is programmed with
the Edit Parameters software.
The CWID output is controlled by A/D processor
U111/latch U107. This output is fed to CWID tone
generator U100B/A and turns the tone generator on
and off to create the Morse Code. From the tone gen-
erator the signal is fed to bandpass filter U129A. This
filter passes the 800 Hz fundamental present in the sig-
nal. The output of the filter is jumpered by P106 on
J106, pins 2/3 and P107 on J106, pins 4/5 to the sum-
ming amplifier and applied to gate U118D, and to the
modulation input of the Exciter.
The input and output connectors for the MAC are
defined as follows.
6.10.12 P101 SIGNALING CONNECTOR
The signal interface connector P101 (64 pin) con-
nects the Address and Data buses and control lines to
the backplane connector. See Figures 6-18 and 6-19.
Pins 1-10 ADDRESS BUS
Pins 33-42
This provides a path between the MPC main pro-
cessor and the processor and memory of the MAC.
This bus retrieves information programmed into mem-
ory for the operation of the MAC.
Pins 11-14 DATA BUS
Pins 43-46
This data bus provides a means of transferring
data to and from the processor on the MAC with
peripheral devices in the MAC.
Pin 15 MREQ
A memory request line operates in conjunction
with the Read/Write lines. These provide the ability to
read from or write to the processor memory.