Loss of Signal

Common issues related to Loss of Signal are:

1. Power off at the RTU- A quick visit to the site will give you the opportunity to see that the main power is still on that feeds the RTU cabinet. Although most Micro-Comm RTU’s have battery backup, there is a possibility that the battery is faulty and not able to power the RTU long enough to give you a power fail condition. This means the RTU will immediately go off as soon as power is lost, resulting in a Loss of Signal.

2. Faulty radio- Even though the radio is ON, and you can hear telemetry data, there may be an issue with the radio’s ability to transmit, which without proper tools is hard to diagnose. Simply exchanging the radio with a known working unit is a quick way to determine if it is faulty.

3. Faulty power supply- If a power supply is weak, it may not be able to supply enough current when the radio is transmitting. Note the radio may pull about 4 amps or more when transmitting and the power supply simply may not be able to produce the necessary power. You may test the power supply by using a voltmeter to monitor voltage while keying up the radio to transmit. The voltage should not drop more than ½ a volt DC. Any more will indicate a faulty power supply. Also, the radio may make an unusual beep if it cannot get enough current to transmit. A simple way to diagnose a faulty power supply is to exchange it with a known good working unit.

4. Faulty Personality Module- on M1500’s, M1550’s, M1650’s and similar, there is a STATUS light just below the POWER light. If the status light is off or blinking, the RTU most likely will be in Loss of Signal. In most cases, replacing the personality module will fix this issue.

5. Antenna/coax issue- Visually inspect the antenna and make sure it is intact, has no missing elements and is pointing in the correct direction. Make sure coax is not loose and swaying in the wind. Other things related to the antenna system that can cause LOS are faulty lightning arrestor and patch cord (small cable that goes from lightning arrestor to the back of the radio).

On most all Micro-Comm controllers, COM1 is used for
radio communications. RXD will flash when you hear sound
on the radio as data is received. TXD will come on for a
short duration when the RTU keys up the radio and transmits
data.

Other things to consider when diagnosing a Loss of Signal:

1. In some cases, the Loss of Signal may be caused by another site that communicates with the site in question. This could be the central OR another site that relays to the site in question. These situations may be a little harder to diagnose. Call the Micro-Comm service department for help.

2. In very rare cases, another radio system may be interfering with the RTU’s ability to communicate properly. Signs of interference normally will be sounds on the radio that are skewed, unusual, voice or any sounds that do not sound like what you normally might hear. If you suspect interference, contact the Micro-Comm service department for assistance.

3. If the radio is warmer than normal, it could be a sign of a short in the antenna system which includes the patch cord, lighting arrestor, coax and antenna.

Learn more about antenna and coax issues here

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