Specifications

H.6.10 VSWR PAL
This PAL contains resettable VSWR trip counters.
H.6.10.1 Single VSWR Trip
When the VSWR PAL U11 receives a single active high VSWR
trip signal from either one-shot, it executes the following func-
tions:
a. The 4 Second Timer Request output will go logic high and
start the 4 Second Timer. The 4 Second Timer output will
go logic high, and is connected back into the PAL.
b. During the 4 Second long Timeout, the Blink output is
logic high, and the VSWR Test Status and J6-9 is logic low.
This low pulse holds the VSWR Test Status LED on the
Control front panel RED for 4 seconds. This keepstheLED
on long enough for the operator to see that a VSWR trip
occurred.
c. The VSWR PAl will count to one internally.
d. After the Timeout pulse goes low, the LED will return to
GREEN and the PAL counter will reset itself to zero.
H.6.10.2 Multiple VSWR Trips
If 5 VSWR trips occur within approximately 20 seconds, the
transmitter will Foldback power by one step. One VSWR trip is
uncounted or removed every 4 seconds.
Refer to Figure H-3, VSWR Logic Timing Diagram, for the
following discussion.
When the VSWR PAL receives more than one Antenna VSWR
trip signal from the one-shot, the PAL will continually count the
number of trips.
a. If only two trips occur as shown on the left side of the
drawing, the Blink output will only go high for 4 seconds,
and 8 seconds after the last Antenna VSWR pulse, the
counter will be reset to zero.
b. If four trips occur as shown in the center of the drawing,
the counter will count up to four and begin counting down
again if no additional trips occur.
c. The right side of the drawing shows that if the counter is
set to two and three more trips are registered, the Antenna
VSWR output goes high for 250uS.
When Antenna VSWR goes high, TP34 Antenna VSWR Fold-
back goes low and generates a 250uS Antenna VSWR-L at J6-1.
a. This will cause the Controller to foldback the power level
by one increment (0.5 dB is the first increment) and latch
the Antenna VSWR and Analog Input Power Foldback
LED’s on the Control front panel RED.
b. If five more VSWR trips occur, the power output reduced
by additional steps.
Operation for Network VSWR is the same, except the output is
at J6-5.
Refer to the Controller Section for more information concerning
the foldback levels and recovery time.
H.6.11
VSWR Self Test
The VSWR Self Test logic circuits are located on the Controller
and Output Monitor board. The Controller generates a VSWR
Test Request-L pulse, whenever any of these conditions occurs:
a. The transmitter is turned on at any power level.
b. The power level is changed. For example, LOW to MED
or MED to HIGH.
c. The VSWR TEST push-button on the LED board is de-
pressed.
H.6.11.1 Successful VSWR Test
On the Output Monitor board, the incoming VSWR Test Re-
quest-L pulse at J6 performs the following:
a. Both VSWR Test Circuits Drivers pull the inverting inputs
of both VSWR Comparators high, simulating VSWR
faults.
b. U11-4 goes logic high, which triggers the 4 Second Timer
and activates the Blink output to turn the VSWR Test LED
RED.
c. Inverter U14-2 goes logic high and forms a pullup supply
for Q46 via CR154. This allows a Network VSWR fault to
be generated at the same time as an Antenna VSWR fault.
d. If the VSWR PAL receives both the Antenna and Output
Network input signals within the 4 Second Timeout pulse,
the Blink signal is released after four seconds and the
VSWR Test LED returns back to GREEN. This is the
indication that a successful VSWR Test has been per-
formed.
H.6.11.2 Unsuccessful VSWR Test
a. If the VSWR PAL does not detect both VSWR trips before
the Timeout, the Latch output will go high and remain
high. This will latch the VSWR Test Status LED RED to
indicate that the test failed.
NOTE
The only way to clear the LED is to pass a successful test.
H.6.11.3 Testing The VSWR Test Circuit
A method of testing the VSWR Self Test logic is as follows:
a. Pressand hold the VSWR Inhibit switch S21 on the Output
Monitor.
b. Press the VSWR Self Test push-button on LED board.
c. After 4 Seconds, the VSWR Self Test LED should remain
RED.
d. Release the VSWR Inhibit and press the Self Test again.
e. After 4 Seconds, the VSWR Self Test LED should return
to GREEN.
H.6.12
Manual VSWR Trip
Manual VSWR Trip push-button switches are available on the
Output Monitor board to test VSWR tripcomparatorsand VSWR
fault counting logic. Switch S11 is a manual trip for the Antenna
VSWR logic, and switch S4 is a manual trip for the Network
VSWR logic. Each switch simulates a VSWR by grounding one
side of the detector transformer. This causes current to flow
through transformer which is rectified into a positive DC voltage
02/17/04 888-2339-002 H-5
WARNING: Disconnect primary power prior to servicing.