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External RF interference examples

2022/04/18 > Back

Movie: Moon
The main actor Sam is an astronaut who has been stationed in the moon for many years to carry out mining work, and the robot Gerty tells him that the communication antenna on the lunar base can no longer be connected to the earth in real time after accidental damage caused by a solar storm, so Sam can only record videos and send the files to the family on the earth, each file transmission takes 3 months to reach the earth. This went on for almost 3 years until one day....

Spoiler alert----------

In fact, the main actor's company Lunar Industries deliberately built an interference-emission tower on the lunar base which constantly emitting noise to interfere with the communication antenna.

H&L wants to tell you: This kind of story does not only happen in the movie.

A lot of times we only emphasize electromagnetic interference inside the machine, but there are still some things that disrupt communications and are present externally. We briefly lists some of the most common types of interference that may be intentional or unintentional, but the majority are beyond your control.

1. Co-channel: Caused by more than one transmitter communicating on the same channel due to improper frequency coordination, deteriorating or malfunctioning equipment, or anomalous propagation.

2. Adjacent channel: Caused by a transmitter operating on an adjacent frequency and its energy spilling over into the desired receive channel.

3. Spurious emissions: Caused when a transmitter emits on frequencies on which it is not meant to operate. This can be observable by poor audio quality or connectivity.

4. Natural occurrences: Caused by natural events such as solar flares, northern lights, and other electromagnetic activities.

5. Intentional interference: It is performed by an actor with a willful intent to disrupt, disconnect, or degrade communications.

6. Intermodulation: Occurs when energy from two, or more, transmitters mix together to produce spurious frequencies that land in the desired receive channel. Third-order mixing products are the most common and usually, this occurs from nearby transmitters. The solution to this problem could be coupled with a narrow frequency filter that allows the signal to pass through the transmitter to the antenna, while the signal returned by the antenna feeder is sifted along the isolator.

7. Fundamental receiver overload: This is normally caused by a strong, nearby, transmitter simply overloading the receiver front-end or other circuitry, causing interference or even suppression of the normal received signal. The only solution is to install a filter on the line of the receiving antenna to let the desired signal pass through, so that the overloaded signal is attenuated.

With today’s increasing use of wireless devices, broadcast, communications, military and other RF sources all competing for radio spectrum, the chances of radio frequency interference (RFI) will only increase. With the proper tools, broadcast and communications engineers are able to quickly identify and eliminate sources of interference as they are detected.

Data resources: www.cisa.gov; interferencetechnology.com; www.2cm.com.tw