Application Examples of Portable Spectrum Analyzers for Radio Signal Monitoring

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Application Examples of Portable Spectrum Analyzers for Radio Signal Monitoring [Copy link]

Portable spectrum analyzers have become a common choice for radio interference detection and analysis, especially for on-site interference troubleshooting and tracking and positioning applications, due to their rich functions, excellent performance, compact size, light weight, and easy portability and operation. In order to give full play to the best performance of the equipment, it is necessary to operate the equipment appropriately according to the specific use environment and occasions. The following takes the portable spectrum analyzer FSH of Rohde & Schwarz as an example. Explain the optimization settings and usage tips for troubleshooting radio interference.

General operating tips

1) To achieve the maximum scan speed at the beginning, use a wideband full-span scan with coarse resolution and set the measurement time to the minimum value.

2) Once the frequency range of interest is determined, use the start and end frequencies to limit the frequency band and reduce the values to improve resolution and sensitivity

3) When running a full span sweep, you can switch to dual trace mode and select the frequency of interest by marking

Dual trace mode

4) Stop full span scanning, the receiver automatically switches to fixed frequency mode, the maximum IF real-time bandwidth reaches 10MHZ, and the signal can be analyzed and demodulated by zooming in and out.

When a spectrum analyzer is used in conjunction with an active directional antenna to track and locate interference, the following operations can be performed:

1) Tune the spectrum analyzer to the center frequency of the target interference signal

2) The demodulation bandwidth must be greater than or equal to the bandwidth of the interference signal to obtain maximum sensitivity (if the demodulation bandwidth is too narrow, the spectrum analyzer will only measure part of the RF level, which will reduce the system sensitivity)

3) Turn off automatic frequency control and manual gain control to avoid the automatic adjustment effect of the receiver affecting the measurement results.

4) Turn on the average detector to provide a stable level reading and increase the measurement time to 200 milliseconds to improve stability

5) Turn on the Tone function to monitor the audio tone, which helps to locate the signal without having to keep watching the level value displayed on the screen; if the signal is too strong, turn on the attenuator ATT to avoid overloading the receiver

When the interference signal is very close to the useful signal, you can operate in the following way

1) Set the receiver to the center frequency of the useful signal and set the span to 10 MHz

2) Only the useful signal spectrum is displayed in the wideband spectrum

3) Use the zoom function to highlight the spectrum peaks outside the center frequency. Other peaks may be interference signals.

4) Select the average function to smooth the displayed curve

5) Set the measurement time to 100 milliseconds or longer.

When the interference signal and the useful signal have the same frequency but are not transmitted at the same time, the following operation can be performed:

1) Set the receiver to work at the center frequency of the useful signal and the span to 10 MHz

2) Select the spectrum plus waterfall display mode

3) Set the IF spectrum to maximum hold mode and set an appropriate measurement time, such as 100 milliseconds

4) It is obvious from the waterfall diagram that after the useful signal is emitted, there is an interference signal with an uncertain emission time; if you only take a screenshot of the spectrum, you cannot capture these two signals well, but you can easily monitor them in the waterfall diagram

When a short-term interference signal is hidden in a stable useful signal, bracketing the same frequency can be operated in the following way

1) Use full span to scan and display the spectrum, such as GSM900 downlink 935MHz-960MHz

2) It is difficult to distinguish short-term interference signals among the large number of signals displayed

3) By activating the trace differential operation mode, the spectrum at the time when the receiver DIFF MODE button is pressed is saved as the reference spectrum

4) Each subsequent measured spectrum will be subtracted from the reference spectrum.

5) Stable signals present in both spectra will be suppressed, while new patterns not present in the reference spectrum will be revealed

6)这种模式可显著降低需要对其进行分析的峰值信号的数量，从而很方便的看出偶发干扰信号。

The above is the optimization settings and usage tips for using a portable spectrum analyzer to troubleshoot radio interference summarized by Antai Testing . You can use it as a reference.