Setting up the high SWR alarm
The high SWR alarm provides an alarm contact which could be used to turn off a transmitter or linear
amplifier in the event of a high SWR. The contact is available at the two pin green socket on the rear of the
meter. A mating plug is supplied with the meter. The contact can handle a maximum of 50 Volts and up to
500mA of current. The contact is optically isolated from the rest of the circuit and is not polarity conscious.
This menu item allows the user to select the contact to be either normally open or normally closed. A
simple method of connection would be to put the contact in series with the key line to the transmitter and
set the contact to be normally closed.
This item decides whether the alarm will be manually reset or auto reset. In manual reset, when the SWR
alarm threshold is exceeded the relay changes state. This will normally cause the transmitter to be cut off,
depending on the external wiring to the alarm contact. The relay will remain in this condition until the
button is pressed. If auto reset is selected, the meter resets the alarm after 3 minutes and again after 6
minutes. If the fault has cleared the transmitter will operate normally. If the fault persists the alarm is
locked on until manually reset.
The final item in the alarm setting menu is the SWR alarm threshold value. There are four choices. 1.50:1,
1.70:1, 2.00:1 and 3.00:1. Long presses of the button will cycle through these options. When the desired
value is displayed, a short press of the button will exit the menu.
The final menu display will indicate if any changes have been made. Changes are stored in non-volatile
memory. If no changes were made, the second line is omitted.
