SNV-12 Operations Manual
1-1
1
Overview
1.1
Scope
This instruction manual provides the information necessary to install and operate the SNV-12
DSP-based, 12 Site Voter.
1.2
Description
1.2.1
General
The SNV-12 will select, from up to 12 individual sites (or 36 in an expanded system), the input
with the best signal quality. For FM receivers, the SNV-12 votes based on the noise level
present in the received signals. Alternatively, a full Signal-to-Noise Ratio (SNR) calculation
works best with AM or HF systems. Individual plug-in Site Voter Modules (SVMs) use digital
signal processing (DSP) to measure noise and speech signal levels and to calculate the SNR.
Pilot tones or External COR inputs may be used to inform the voter when the voting receiver is
unsquelched. A Control Processor Module (CPM) controls the Site Voter Modules and a
Console Interface Module (CIM) provides monitoring of the voted signal. Together they
provide an interface to a command console or computer terminal.
1.2.2
Card Cage and Backplane
The Card Cage is a 19" wide EIA standard rack-mounted Eurocard cage equipped with a
backplane board that the modules are plugged into. The modules PC Boards are 100 x 220
mm. The card cage height is 5.25" (3RU) tall, 19” wide, with a depth of 11". An AC input
module and a power transformer assembly are located on a metal panel that is mounted to the
backplane. The AC module is a combination AC line filter, power cable connector, input
voltage selector and fuse holder. The backplane interfaces the outside world via D-
subminiature and terminal strip connectors, and internally to the plug-in modules via 60-pin
card edge connectors. No active or passive electrical components reside on the backplane
board.
1.2.3
Power Supply Module
The Power Supply is a single-board module that plugs into the left-most slot in the backplane.
The power supply's backplane connector is offset relative to the connectors for the other
modules; this prevents improper location of the Power Supply Module in the slots reserved for
the other cards. In turn, these other modules cannot be plugged into the Power Supply slot.
The Power Supply incorporates a dual-primary line transformer with a bridge rectifier and filter
capacitors to provide a +15V unregulated DC bus. The bus feeds a linear regulator that
supplies all modules with +12 VDC, and the bus also feeds a switching regulator that provides
-12 VDC. Each individual Site Voter Module contains a switching +5V regulator operating
from the +15V bus. The Power Supply can be powered by either 115 or 230 VAC or +12
VDC. A trickle charger output is provided at the DC Supply terminals for use with battery
backup operation.
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