In 2010, the Civil Aviation Shandong Air Traffic Control Branch reflected in the Shandong Provincial Radio Management Office, Jinan Airport, the high-frequency ground, air communication station in the near, continuous noise interference, the transceiver RSSI value displayed by normal circumstances, 908dBm or less Raise to -101dBm, thus affecting the reception of the ground receiver to the remote aircraft communication signal, which makes the potential hazard of navigation safety have increased.
In this regard, the Shandong Radio Management Office is very concerned, and the organizational strength of the monitoring station is immediately arranged. After multiple tests, several related signals were found, but they were analyzed and verified, and they were uninterrupted, and they were excluded one by one. Since the interference signal is very weak, ordinary test equipment is difficult to capture the interference signal, more difficult to measure and position. Wireless Communication Test System Integration and Solutions Provider Beijing Zhongtong Huaying Technology and arrived at the end of December at the end of December to bring the Tektronix H600 Portable Wireless Signal Detection. The Tektronix H600 is a meter with real-time spectrum analysis functions produced by Tektronix, which has a strong capture capability for transient and buzzing small signals, which are fully validated in the interference finding process.
The technical staff of Shandong Radio Monitoring Station and Zhongtong Huaying Technology, based on the early test analysis, considered that the interference signals near the tower were more serious. Therefore, first test the office area of the Tower 1st Floor, it is found that there are several RFID devices in the water supply system, which is used to control the water supply system, so testing near the RFID, it is found that there are indeed multiple interference signals, and the screenshots are shown in Figure 1. Show:
Figure 1: Two transmit signals appear.
However, after turning off the RFID device, the tower reaction interference signal still exists and has not improved. It is not true interference signal that proves that the signal emitted by the RFID device is near the tower operating frequency band.
Subsequently, the testers of Zhongtong Huaying Technology directly came to the tower machine room for testing. Test staff test in the airport tower machine room, there are several signals near 122.900 MHz, see Figure 2:
Figure 2: 122.906 MHz and 122.893 MHz two signals have fallen 122.900 MHz.
Communication channels. Comparison FIG. 3 (the spectrum of the blue large signal, a 122.900 MHz channel call, indicating that the above two signals and some of the signals are the interference signal of the 122.900 MHz channel.
Figure 3: 122.900 MHz channel call instantaneous spectrum.
To exclude external interference factors, the tester has been photographed around the tower in the outdoors, and the meter automatically records the test results (as shown in Figure 4).
Figure 4: Spectrum map at outdoor test.
The road test results, the interference signal is basically unable to receive the interference signal on the ground, and the speculation may be due to too low the terrain. The tester came to the tower middle part of the tower. It was found that the interference signal was still unable to find that the interference signal may not be From outdoor equipment, it is caused by stray radiation of certain devices indoors.
Figure 5: Signal intensity instructions near the interference cabinet.
So the tester returned to the tower machine room and tested indoor equipment. When the spectrometer is close to one of the equipment cabinets, the interference signal is significantly enhanced (as shown in FIG. 5), it is inferred that a device in the cabinet produces an interference signal. After breaking up the equipment in the cabinet, it is found that one of the domestic photoelectric conversion equipment is the source of the interference signal. The following figure is the signal change of the cursor before and after the device is closed:
Before
After closing
Close the photoelectric conversion device, the RSSI index of the transceiver is restored below -110dBm, the noise of the sound of the sound is disappeared, and the air communication is basically normal, and the interference source is further proof.
This RF interference investigates some of us, and there are many kinds of civil aviation interference, such as a variety of devices from interior of the machine room. Some seemingly unrelated devices may also generate RF signal leaks, which interferes with communication equipment. The photoelectric conversion device II III III was not related to the principle of the component, the equipment aging, the system stability is poor, so that the equipment has spurious and radiation signals when working for a long time, and the high-frequency ground empty communication station is Continuous noise interference with frequency 122.900 MHz. The case also explains that it is an indispensable procedure and measures to rule out the system itself and other devices in the machine room when investigated RF interference.
Source: Tektronix, Read more
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