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Noise
Generator

NG 500

User Manual

UNAOHM S.r.l. - Via G. di Vittorio 49 - 20068 Peschiera Borromeo (MI) Italy

Tel . +39.02.36577787 Fax +39.02.51650195

Web: www.unaohm.it E-mail: [email protected]

Содержание NG 500

Страница 1: ...oise Generator Noise Generator NG 500 NG 500 User Manual UNAOHM S r l Via G di Vittorio 49 20068 Peschiera Borromeo MI Italy Tel 39 02 36577787 Fax 39 02 51650195 Web www unaohm it E mail info unaohm it ...

Страница 2: ...ERATOR TO THE DEVICE UNDER TEST 9 7 MAIN APPLICATIONS 9 7 1 FREQUENCY RESPONSE MEASUREMENT 9 7 2 MEASUREMENT OF DISTANCE TO FAULT OPEN CIRCUIT OR SHORT CIRCUIT ON A CABLE 13 8 APPENDIX THERMAL NOISE 16 9 WARRANTY 19 UNAOHM S r l reserve the right to change product specifications at any moment and without notice regardless of whether the change is of technical or commercial nature or being implemen...

Страница 3: ...r dust Do not turn on the instrument immediately after transferring it from a very cold place to a hot one to avoid condensation Do not obstruct the instrument s cooling slit fenditures or place it near strong sources of heat For prolonged use in the lab or in fixed places the instrument should be removed from the carrying case to allow for better heat dissipation Do not apply DC or RF voltages to...

Страница 4: ...r associated with it For example connecting a filter under test between the generator and the meter will let through only the portion of the white noise which falls within the filter s frequency response and this is shown on the meter in spectral fashion The accuracy of this simple measuring technique makes the set up just described comparable to units such as sweep markers or spectrum analysers w...

Страница 5: ...r supply UNAOHM BCH 15 0 9 4 2 W 220 Vca on without battery 4 1W 220 Vca off with a flat battery 10 5 W 220 Vca on with a flat battery MECHANICAL Size 150 x 100 x 25 mm Height x Width x Depth Weight without battery 0 200 kg Finishing Two compartment nylon bag instrument and power unit AMBIENT Calibrating Temperature 23 C 5 C Operating Temperature 5 to 40 C Storing Temperature 10 to 60 C Relative H...

Страница 6: ...ORIES N 1 External PSU battery charger BCH 15 0 9 N 1 Two compartment nylon bag N 1 Instruction manual 4 2 OPTIONAL ACCESSORIES 1 6V 1500mAh Ni MH Five AA size elements battery pack 5 CONTROLS AND CONNECTIONS See Figure 1 Figure 1 Control connection panel ...

Страница 7: ...rom a 230V mains through it 6 OPERATING INSTRUCTIONS 6 1 PREPARING THE INSTRUMENT FOR USE For safety reasons the instruments purchased with the battery leave our warehouse with the connector terminated lead of the battery disconnected It is therefore necessary that the buyer before using the instrument reconnects it This operation may be carried out by simply removing the instrument from its bag a...

Страница 8: ...UNAOHM NG500 Rev 0 7 Figure 2 Battery connections 6 2 POWER SUPPLY The generator as already mentioned in the specification section may be powered in three modes ...

Страница 9: ... ON battery is flat 2 By an external source of DC power from 12 to 16 VDC capable of providing at least 240 mA current to apply to the EXT DC IN 12 16 V 4 input jack The PWR ON 2 LED lights up to indicate that the power supply is available and the unit is operating 3 By means of a 230 Vac mains through an external power supply BCH 15 0 9 connected to the EXT DC IN 12 16 V 4 input The same power su...

Страница 10: ... units which precautions should be taken and any warnings to take into consideration to avoid the risk of incorrect measurements The appendix will deal with them in more detail together with some technical matters related to the measurements carried out 7 1 FREQUENCY RESPONSE MEASUREMENT A simplified structure of a typical centralized installation is given in figure 3 Note the antenna headend and ...

Страница 11: ...tor of the field strength meter tuning it to both the frequency band required VHF UHF or SAT 2 Set the attenuator of the meter to an input level between 70 and 80 dBµV 3 Switch the meter to spectrum function either expanded partial view of the bandwidth or full depending on how much of the bandwidth you wish to cover Note Ideally the pattern observed should have a constant amplitude level througho...

Страница 12: ...of the device will be determined by dB loss dB ref dB measurement dB gain dB measurement dB ref Warning if the device under test is active with gain and wideband be careful since the power increase due to the extended bandwidth may easily cause overload remember that each time the bandwidth is doubled corresponds to a 3 dB increase in signal level Therefore if necessary engage some attenuation on ...

Страница 13: ...tor supplies 80 dBµV each 1MHz bandwidth 2 Apply the NG500 generator signal directly to the input connector of the FSM set to 90 dBµV full scale and 1 MHz bandwidth as per Figure 4 Check for a reference level say at 81 dBµV Connect now the amplifier under test between the NG500 and the FSM with the same 1MHz bandwidht as per Figure 4 and take the level reading for example 96 dBµV The amplifier gai...

Страница 14: ... in Figure 6A Connect the line in question to the T connector If it is mismatched standing waves are created in it which are visible on the screen of the FSM with half sine oscillations as shown in figure 6B The measurement consists of finding out the space or frequency range between two minima or maxima which we will indicate as ΔF This ΔF frequency may be used to calculate given the type of coax...

Страница 15: ...the bandwidth of the meter which must be in any case much lower than ΔF It is evident that for small mismatches it is not possible to carry out a reliable measurement since the standing waves are not clearly marked Example Suppose that in the installation detailed in Figure 3 the signal is not present down column A at the user s outlets 3 4 and those that follow We can safely say that the failure ...

Страница 16: ...urement This distance corresponds to the approximate height of one storye which would then correspond to where the D2 shunter is It is therefore evident that either the cable or the shunter is defective To find out which one is defective disconnect the cable from the shunter D2 and connect a 75 Ω load termination if the standing waves viewed on the FSM disappear the defect is not in the cable but ...

Страница 17: ...tion of the electrons the difference in potential varies continuously in a totally irregular manner while in any case remaining at an average of zero We are therefore dealing with zero average voltage with momentary values that are extremely low that may be noted only if highly amplified This does not however signify that it is less real than the normal voltages obtained by the generators Thermal ...

Страница 18: ...efore be represented by the circuit in Figure 8 in which Figura 8 Equivalent circuit with pass band filter K 1 38 10 23 Joule degrees Kelvin Boltzmann constant T absolute temperature in degrees Kelvin zero degrees centigrade corrisponds to 273 K B bandwidth in Hz R resistance value in Ω For example If R has a value of 1000 Ω at an ambient temperautre of 20 C 273 20 293 K and the filter has a bandw...

Страница 19: ...f the generator i e 1000 Ω the voltage is decreased to half 2 µV On the basis of what has been briefly exposed the noise generator NG500 may be represented with the equivalent circuit as shown in figure 11 where the amplifier A has a bandwidth of 2000 MHz and an internal resistance of 75 Ω Figure 9 Final equivalent circuit ...

Страница 20: ...ed circuits are used the supply of spare parts is guaranteed up to the depletion of our stock and depending on the possibility of procuring them on the worldwide market The repair of instruments out of warranty is normally carried out and then the final cost is communicated to the customer the eventual request for an estimate of this cost prior to the actual repair must be made at the moment the i...

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