3.9 RF preamplifierA device, whose noise factor (NF) in the measurement band is within 9 dB, to amplify themeasurement signals to measure the signals which are of the measuring limit or below, or to securethe dynamic range. The measurement is to be carried out by setting up the RF amplifier before thespectrum analyzer. The measured values shall be corrected by deducting the value of amplifiedproportion by the RF amplifier. It is permitted to use the RF preamplifier which is housed in thespectrum analyzer or the active antenna. When using the RF preamplifier, it must be ensured tocheck the spectrum distributions before and after the RF preamplifier connection in order to confirmthat the measuring value is shifted in proportion to the amplification by the RF preamplifier. In thecase where the actual amplified volume of the measurement value does not conform to theamplification volume preset at the RF amplifier, the RF preamplifier shall not be used.In addition, confirmed data shall be recorded in the measurement report.Example: MH648A made by Anritsu Corporation, 8449B made by Agilent Technologies3.10 Coaxial CableThe coaxial cable shall have the impedance of 50 and connects the antenna, the probes or the RFpreamplifier, and the spectrum analyzer. The cable loss proportion shall be added as a correctionvalue to the measurement values of the spectrum analyzer.3.11 Artificial Power Circuit NetworkThis is also called AN (Artificial Network) or LISN (Line Impedance Stabilization Networks) andsimulates the high frequency distribution constant or the impedance characteristics of the vehicle'swire harness which is observed from the terminals of automotive electric and electronic parts. Oneswhich conform to CISPR 25 or ISO 7637-1 shall be used. Since the measurement port contained inthe artificial power circuit network is not used in this standard, it shall be connected with 50terminal. Fig. 7 and Fig. 8 shows its configurations and characteristics. In the case where theoperations of specimens cannot be assured as this artificial power circuit network is connected, orwhere the condition becomes obviously different from the mounting condition on the actual vehicle,the artificial power circuit network shall not be used. This is also the case when the certified voltageand the certified current of the artificial power circuit network are exceeded. The reason that its usewas avoided shall be stated in the test plan sheet and the test report.