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COMMAND FAULT CHECKING
When a command is issued remotely, there are numerous things that can keep the desired result from occurring. If
a status signal exists, there is an easy way to compare the fact that a relay was energized and the action actually
took place. Assume the following:
Command 1 = TX ON AIR (latching)
Status 1 = TX ON AIR
Here is the virtual channel expression for a fault indication:
R1 XOR S1
R1 represents the state of the relay for channel 1 which is set to latch the transmitter on the air. S1 represents the
status from the transmitter confirming that it is actually on. XOR is the exclusive OR operator meaning that either
one or the other condition is true but not both. The truth table looks like this:
R1
S1
Result
Condition
0
0
OK
TX off
0
1
Fault
TX on with no command!
1
0
Fault
TX command on but no response
1
1
OK
TX on
If no status signal is available, there may be a metering value you can use like this:
R1 XOR (M1>90)
To prevent false alarms at startup, add a little delay to the alarm.
VSWR COMPUTATION
Displaying VSWR on an ARC Plus is easy using virtual channels.
Meter
Source
Label
Units
1
Plus-X
Forward Power
kW
2
Plus-X
Reflected Power
W
3
Virtual Channel
Rho*
4
Virtual Channel
VSWR
*Reflection coefficient, not usually displayed but needed for calculation
Meter 3:
SQRT (M2 / (M1 * 1000))
Meter 4:
(1 + M3) / (1
–
M3)
