Update rigctl.1 set_ant

doc/man1/rigctl.1

@@ -667,7 +667,7 @@ and
 .IP
 Number is 1-based antenna# (\(oq1\(cq, \(oq2\(cq, \(oq3\(cq, ...).
 .IP
-Option depends on rig..for Icom it probably sets the RX only flag. See your manual for specific option values.
+Option depends on rig..for Icom it probably sets the RX only flag as in the IC-7851. See your manual for specific option values. Most rigs don't care about the option.
 .
 .TP
 .BR y ", " get_ant " \(aq" \fIAntenna\fP \(aq