Tips for using spectrum analyzer

1. What is a spectrum analyzer? A graphical tester that analyzes signals in the frequency domain. It displays the distribution of signal amplitude by frequency in a graphical manner, that is, the X-axis represents frequency and the Y-axis represents signal amplitude.

2. Principle: Use a narrow-band pass filter to select the signal.

3. Main functions: Display the spectrum, amplitude and frequency of the measured signal. It can display the whole picture and select the bandwidth test.

4. Measurement Mechanism:

1. Compare the measured signal with the reference frequency and reference level in the instrument. This is because the essence of many measurements is level testing, such as carrier level, A/V, frequency response, C/N, CSO, CTB, HM, CM and channel average power.

2. Waveform analysis: Through the 107 option and the corresponding analysis software, the line waveform of the TV is analyzed to test the video indicators, such as DG, DP, CLDI, modulation depth, frequency deviation, etc.

5. Operation:

1. Hard keys, soft keys and knobs: They are the basic operating methods of the instrument.

1. Three hard keys and one large knob: The function of the large knob is set by the three large hard keys. Press the frequency hard key once, and the knob can fine-tune the center frequency displayed by the instrument; press the sweep width hard key once, and the knob can adjust the frequency width of the instrument sweep; press the amplitude hard key once, and the knob can adjust the signal amplitude. When you turn the knob, the center frequency, sweep width (start and end frequencies), and dB of the amplitude are displayed on the screen at the same time.

2. Soft keys: On the right side of the screen, there is a row of unmarked buttons arranged vertically. Their functions vary with the project. Whatever is displayed on the right side of the screen corresponding to the button is that button.

3. Other hard keys: There are ten hard keys in the instrument state (INSTRUMNT STATE) control area: RESET, CANFIG, CAL, AUX CTRL, COPY, MODE, SAVE, RECALL, MEAS/USER, SGL SWP. There are four hard keys in the cursor (MARKER) area: MKR, MKR, RKR, FCTN, PEAK SEARCH. There are six hard keys in the control (CONTRL) area: SWEEP, BW, TRIG, AUTO COVPLE, TRACE, DISPLAY. There is a BKSP back in the numeric keypad, and on the right side of the numeric keypad are four ENTER keys in a vertical row, which are also unit keys. The three hard keys above the large knob are window keys: ON, NEXT, and ZOOM. The two arrow keys STEP below the large knob are used in conjunction with the large knob to adjust the volume up or down.

(II) Input and output interfaces: located in the lower row of the panel. TV IN is the signal input port for measuring video indicators; VOL INTEN is a set of knobs inside and outside to control and adjust the volume of the built-in speaker and screen brightness; CAL OUT is the instrument self-test signal output; 300Mhz 29dBmv instrument standard signal output port ; PROBE PWR instrument probe power supply; IN 75Ω1M-1.8G test signal total input port.

(III) Test preparation:

1. Restrictive protection: specifies the maximum input RF level and the maximum voltage value that causes permanent damage: DC 25V, AC peak-to-peak 100V.

2. Preheating: The test must wait until the OVER COLD disappears.

3. Self-calibration: Self-calibration should be performed after three months of use or before important measurements.

4. System measurement configuration: Configuration is to input some measurement parameters before measurement, eliminating the need to input parameters every time measurement is made. Content: test items, signal input mode (frequency or channel), display unit, format, noise measurement bandwidth and sampling point, frequency point for measuring CTB and CSO, test line selection, etc. Configuration steps: Press MODE key - CABLE TV ANALYZER soft key - Setup soft key to enter the setup state. Details are tune config tuning configuration: including frequency, channel, format, level unit. Analyzer input input configuration: whether to add preamplifier. Beats setup beat frequency setting, frequency point for measuring CTB and CSO (frequency offset CTB FRQ offset, CSO FRQ offset). GATING YES NO whether to select the test line. C/N setup carrier-to-noise ratio setting: frequency point (frequency offset C/N FRQ offset), bandwidth. . (IV) Methods for reading results: 1. Level reading: mainly use reference level REF. The top horizontal line on the instrument screen graph is the reference level line. The level indicated by this line is the reference level, and its value and unit are displayed in the upper left corner of the screen. The value of the reference level can be changed: press the AMPLITUDE hard key and rotate the large knob to change it, and the number will be displayed at any time. The decibel number dB/DIV of each grid of the graph is displayed in the upper left corner of the screen. 2. Reading of frequency: The three vertical lines of the center frequency, start frequency, and end frequency in the graph, and the frequency numbers represented by each are displayed at the bottom of the screen. The center frequency is adjusted by rotating the large knob with the Frequency hard key; the start and end frequencies are adjusted by rotating the large knob with the Span hard key (actually changing the scan width). 3. Use of cursor: Press the MKR key, and a flashing cursor will appear on the screen curve. The level and frequency of the cursor position are displayed in the upper left corner of the screen. The cursor can be moved arbitrarily, and the frequency and level of the position will be displayed at the position where it is moved. 4. Printing and storage 5. Video test VI. Common tests - spectrum test and channel test (Cable TV analysis): Press the MODE hard key, and two soft keys will be displayed on the screen: spectrum test and Cable TV analysis. Press the corresponding soft key to enter the respective test items. 1. Spectrum test: Use the three hard keys and the large knob to perform general analysis. 2. Channel test: Press the Cable TV ANALIZER soft key, then the Channel Test soft key to display the test menu (four pages in total), press the CHINAL SELECT soft key, and use the numeric keypad to enter the identification frequency of the channel to be tested (the analog TV channel is the image carrier frequency, and the digital channel is the channel center frequency), and then you can test the channel. The menu contents are as follows: LISTEN ON/OFF Sound on/off EM DEV FM modulation depth VIEW INGRESS Image crosstalk CARRIER LVL & FRQ Carrier level/frequency CARRIER/NOISE Carrier-to-noise ratio HUM Hum modulation CROSS MOD Crosstalk modulation CSO/CTBD DEPTH MOD Modulation depth SYSTEM FRQ RSP System frequency response IN CHNL FRQ RSP Channel frequency response DIE GAIN DIF PHAZ Differential gain, differential phase CLDI Color brightness delay difference DIGITAL CH POEWER Digital channel power FM RADIO FM radio VII. Several questions: 1. To measure C/N and CSO: The instrument provides two methods: turn off modulation and do not turn off modulation. To do not turn off modulation, insert a static test line into the modulation signal of the channel being tested, start the instrument's gating function, and normal broadcasting can be uninterrupted. To measure CSO, the beat frequency position must be set in the Setup in advance. So that the instrument can find the beat frequency at the set frequency. 2. When measuring HUM and CM, modulation must be turned off (without turning off the carrier). 3. When measuring CTB, the carrier must be turned off. This is because the CTB product is concentrated near the carrier frequency. After turning off the carrier frequency, both the CTB and CSO products can be seen on the screen. To distinguish which is CTB or CSO, use their relationship with the input level to make a judgment. 4. The following test items require the insertion of a static test line in the field reverse process: measuring C/N and CSO without turning off modulation; measuring CTB;

Front panel diagram