Volume 1
MIL-HDBK-162A
Section 3
15 December 1965
ITEM NAME: DECODER GROUP
TYPE: AN/UPA-50(XN-1)
displayed targets.
TECHNICAL DESCRIPTION
The decode functions of the decoder group are (1)
Inputs
to check a target reply code for parity with a preset code
IFF Video: Mode 1, 2, or 3 SIF code train replies
(passive decode); (2) to check the reply code for bracket
Polarity: Pos
pulse coincidence (bracket decode); and (3) to translate
Pulse Amplitude: 2v plus or minus 0.5v
the reply code, which is in a binary coded octal form,
Pulse Width: 0.30 to 1.0 usec (0.45
usec
into its equivalent decimal number (active decode). As
nom)
a result of these functions, output signals are provided
Pulse Spacing: 1.45 to 2.90, usec plus
for display as the IFF target on an associated radar
or minus 0.50 usec as measured from
indicator, and a decimal number is read out on lamp
pulse leading edges
indicating devices. The IFF target display and the code
Pulse Spacing: 1.45 to 2.90, usec plus
readout are performed in synchronism. A three channel
or minus 0.50 usec as measured from
device, the code readout presents instantaneously the
pulse leading edges
reply codes of three discreate targets. In addition, a
Azimuth Signal: Three ph cursor-bear-
delayed code video output is provided for display and,
when interconnected, the surveillance radar video is
AN/SPA-IA; a 6.3v ac, 60 cyc reference v
passed or mixed with IFF video as an output. Selecting
Range Trigger: 12v nom amplitude; pos
and IFF, radar or mixed output, establishing a preset
polarity; at a repetition rate which
code and an IFF mode of operation, and enabling the
is the same as AN/SPA-IA range strobe
interrogator challenge are functions of operating controls
located on the front panel of the video decoder.
Radar Video: 0.30 to 1500 usec duration
A sector gate generated by the decoder indicator
of individual pulses; 2v (min) amplitude
unit of the decoder group provides a means of selecting
Input and Output
and segregating targets for active readout. This gate is
Impedance: 75 ohms (terminated) Outputs
applied externally to the video sweeps of the associated
Radar Video: Output supplied identical to
radar indicator and internally to the code translation
input; or as a mixed output w/IFF video
circuits. As displayed on a PPI type indicator the sector
Bracket Decode: A single 1.5 usec
gate is defined by azimuth radials and range areas
(nom) pulse
which appear as brightened traces to form essentially a
Polarity: Pos
rectangular shape on the screen. This defined area
Amplitude: Adjustable between 1.5 to 4.Ov
represents in range and azimuth the time during which
Passive Decode: A single 1.5 usec (nom) pulse.
target replies are enabled for active readout. The
Polarity: Pos
placement of the sector gate is a function of the
Amplitude: Adjustable between 1.5 to 4.0v
associated radar indicator controls; the area delimited
Bracket Decode: Normal bracket pulse;
by the gate is adjustable within limits by means of
stretched passive decode pulse (10
azimuth and range controls on the video decoder unit.
usec nom)
The sector gate is also useable for delimiting target
Passive Decode: Passive decode pulse
challenge to the gated area.
(10 usec nom)
RELATION TO SIMILAR EQUIPMENT
Code Video: Same form as IFF input
video, but delayed approx 40.8 usec
Decoder Group AN/UPA-49(XN-1) and Decoder
Polarity: Pos
Group AN/UPA-50(XN-1) are functionally identical units.
Amplitude: Adjustable between 1.5 to 4.0v
They differ only in their application to particular system
Target Sector Gate: Series of pulses;
complex and in minor circuit variations which are
pos polarity amplitude adjustable
necessary to make each group compatible with the
from 0 to 4v
characteristics of associated equipment. The AN/ UPA-
Power Requirements: 115v ac, 400 cyc, 1-ph, 50w
50 is used with Radar Recognition Set AN/UPX-1A and
Radar Indicator AN/SPA-BA. A Video Decoder KY-
INSTALLATION CONSIDERATION
3B7(XN-1)/UPA and a Power Supply PP-3078(XN-1) are
Related Equipment
units common to both groups. A Decoder-Indicator is
Required but not Supplied: For Decoder
the third unit in a group; the KY-404(XN-1)/UPA50 is
Group AN/UPA-50. One Radar Recogni-
used. Decoder Group AN/UPA-50 is a replacement for
tion Set AN/UPX-1A which supplies IFF
the
Decoder
Group
AN/UPA-24.
video inputs and one Radar Indicator
AN/SPA-BA which provides cursor/ant-
AN/UPA-5O(XN-1): 2
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