Reverse Power Protection (-50 Unit With Mod Status 7) - Aeroflex NAV 2000R Operation Manual

Aeroflex Operation Manual
4.8 REVERSE POWER PROTECTION
(-50 UNITS W/MOD STATUS 7 ONLY)
For the following discussion refer to JPN schematic drawing 02-6157-00. With the POWER switch in the
OFF position, relay K101 is in its normally open state. This prevents any damage to the instrument while
it is not in use. On power-up, a reset command is issued by the NAV 2000R CPU board to flip-flop U2.
U2's output turns on Q1 and Q2 providing drive to relay K101's control pin thereby closing the path
between the NAV 2000R output stage and the unit under test.
U1 compares the voltage from the detector circuit composed of R102, CR103 R101 AND C101 to a 2V
reference. Should the detected signal exceed the 2V threshold (approx. +20 dBm of RF input), U1's
output will change state clearing U2 and opening relay K101. In addition, the CPU board is notified of the
tripped condition via the RPPINT discrete output. Maximum trip time is 4 msec. Pin diodes CR103
through CR106 provide high speed protection of the NAV 2000R output by clamping the RF signal to
ground until K101 has opened the RF path. K101 will remain open until the RPPRST line is asserted by
the CPU board.
NAV 2000R SIGNAL GENERATOR - REV. 0 – JULY 26, 2007 - PG 4-28