A field strength meter, as understood from its name, is an instrument that measures field strength (level). It can satisfy high precision measurement of field strength (level), picture/sound ratio, carrier/noise ratio, digital channel power, spectrum analyzer, HUM, intermodulation and return evaluation of TV, FM and CATV systems. The product is equipped with an LCD display that can visually display the measurement data. Brief explanation of field strength Field strength is the abbreviation of electric field strength, which is the magnitude of the electric signal induced by the antenna at a certain point in space to characterize the electric field strength at that point. Its unit is microvolt/meter (μv/m), and for convenience, dBμv/m (0dB=1μv) is also useful. Field strength measurement When the antenna has the same polarization direction as the measured signal in the air, the maximum induced signal can be obtained. Generally, a radio frequency (RF) RMS level meter (voltmeter) can be used to measure it. When the line is well matched, the level value read by the meter is the RF voltage Er (dBμv) obtained by the input port of the meter (generally 50Ω or 75Ω). Er can be expressed by the following formula Er=E+Ga+20lgle-Lf-6---(1) Er is the reading level of the instrument input port (dBμV); E is the electric field strength (dBμV/m); Ga is the receiving antenna gain (dB). If a half-wavelength dipole antenna is used, Ga=0dB; le is the effective length of the receiving antenna (λ/π); Lf is the receiving feeder loss (dB); 6 is the correction value (dB) for converting the open port from the termination value. The electric field intensity E (dBμV/m) can be obtained from equation (1), namely: E=Er-Ga-20lgle+Lf+6---(2) Now give an example for specific description: set the test frequency to 228.25MHz (λ=1.31m) Then 20lgλ/π=20lg1.31/π≈-7.6dB; The receiving antenna is a half-wavelength dipole antenna, Ga=0dB; Lf selects a cable with attenuation of 10dB/100m, and the attenuation is 1dB when the practical length is 10m; the indicator level is 15dBμV. When substituting the above data into formula (2), we get E =Er-Ga-20lgle+Lf+6 =15-0-(-7.6)+1+6 =15+7.6+1+6 =29.6dBμV/m Air Fryer No Oil,Multifunction Air Fryer,Electric Air Deep Fryers,Deep Fat Fryer With Timer Ningbo ATAP Electric Appliance Co.,Ltd , https://www.atap-airfryer.com
May 17, 2023