Operating the meter with the Alarm activated.
When the SWR rises above the alarm threshold, the alarm relay is operated. The contact will close if
“normally open” operation has been selected. It will open if “normally closed” operation has been
selected. This screen is displayed briefly.
The display then reverts to the normal measurement screen, but the yellow color persists.
In the above example, the alarm contacts have been wired to cut off the transmitter. Zero power is
correctly indicated and if manual reset has been selected, it will remain in this condition until reset by
pressing the button.
If the high SWR condition remains, the alarm will be immediately re-triggered. To investigate the cause of
the high SWR, it will be necessary to reduce transmitter power and turn off the alarm through the meter
menu.
If auto-reset has been selected, the meter will apply transmitter power to the load after approximately
three minutes. If the fault condition still exists, the alarm will be re-triggered and the transmitter turned
off. The meter will try again in a further 3 minutes. If both retries are failures, the alarm is locked on until
manually reset by pressing the button. If the fault condition has cleared, the transmitter will continue
normal operation and the screen color will revert to normal.
Additional notes
If the screen becomes blue, it means the power rating of the meter is being exceeded. Reduce power
immediately to prevent damage to the meter.
If the screen flashes red during receive, it means the antenna is picking up strong signals. This normally
only occurs with very large and high antennas and when a thunderstorm is near-by. The meter detects the
lightning. Shut down the station and earth the antennas.
Some unexpected high SWR readings may occur when large RF currents are passing along the braid of the
co-ax cables, depending on where the cables are earthed. This doesn’t occur when the antenna is fed via a
balun. It is also possible for DC currents to flow through the meter if there is, for example, a poor negative
supply connection to the transmitter. These currents may upset the bridge balance especially if the centre
conductor of the co-ax is involved.
