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UNAOHM NG 500 User Manual

Noise generator
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Summary of Contents for UNAOHM NG 500

  • Page 2: Table Of Contents

    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 implemented to comply with legal requirements of specific countries.

  • Page 3: Warning

    UNAOHM 1. WARNING MARK This instrument is in conformity with the following standards and documents: EN 50082-1 - EN 55011 - EN 61000-3-2 - EN 61000-3-3 - IEC 801-2 IEC 801-3 - IEC 801-4 Safety Regulation EN 61010-1 The below-indicated safety precautions and general warnings must be carefully observed during all phases of use, maintenance and servicing of the instrument to avoid damages to persons, animals and property.

  • Page 4: Introduction

    The NG 500 generates white noise in the 5 to 2300 MHz range. The output signal level of the meter depends on the bandwidth of the measuring device (voltmeter, wattmeter etc); in fact the level is directly proportional to it.

  • Page 5: Specifications

    ~ 4 hours (With standard 6V/1500 mAh Ni-MH battery) 4.2 W (on without battery), @220 Vca (With an external power supply, UNAOHM 4.1W (off with a flat battery ), @220 Vca BCH 15/0.9 10.5 W (on with a flat battery).

  • Page 6: Accessories

    UNAOHM 4. ACCESSORIES 4.1. STANDARD ACCESSORIES 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.

  • Page 7: Operating Instructions

    UNAOHM 1. NOISE OUT: BNC output signal connector. 2. POWER SUPPLY / BATTERY LOW PILOT LED: the pilot LED "ON" lights up to indicate that the unit is operating. In DC operation via battery, the pilot LED light blinks when battery capacity is approaching flat status, and switches off when flat status is reached.

  • Page 8: Power Supply

    UNAOHM Figure 2 Battery connections 6.2. POWER SUPPLY The generator, as already mentioned in the specification section, may be powered in three modes: NG500 (Rev. 0)
  • Page 9 UNAOHM 1) By means of the standard 6V dc battery pack. The unit can work continuously for about four hours under ideal operating conditions. The "POWER ON" (2) LED indicates that: ⇒ power to the unit is on when LED lights up.

  • Page 10: How To Connect The Generator To The Device Under Test

    It is therefore important to keep attenuation under control. Two instruments are necessary to carry out the measurement: the NG 500 noise generator and a field strength meter fitted with a spectrum analyser, that will be referred to further on in this manual as FSM.
  • Page 11 UNAOHM Figure 3 Simplified structure of a typical shared installation Figure 3 legenda: -Sistema di antenne riceventi = receiving areal system -Miscelatore = mixer. The operations are carried out in two phases. First the instruments are calibrated connecting the noise generator to the field strength meter thereby establishing a reference level.
  • Page 12 UNAOHM response of each instrument does not guarantee perfect linearity (they both have a certain tolerance on linearity). Furthermore, the display on the tube may appear poorly defined due to the nature of the “noise” signal. To improve it, it may be useful to include a video filter if provided with the field strength meter.
  • Page 13 UNAOHM Figure 4 Connections to check the frequency response of a device under test Figure 4 legenda:-Dispositivo sotto test = Device under test (DUT). -Misuratore di campo = Field Strength Meter (FSM). Example If you wish to measure the gain of a channel amplifier, such as channel 23 covering the frequency range from 486 to 494 MHz (8MHz bandwidth device) : 1) Make sure the amplifier accepts 80 dBµV + 10 log (8) = 89 dB without getting into saturation...

  • Page 14: Measurement Of Distance To Fault (Open Circuit Or Short Circuit) On A Cable

    UNAOHM Figure 5 Channel amplifier response taken as measuring example 7.2. MEASUREMENT OF DISTANCE TO FAULT (OPEN CIRCUIT OR SHORT CIRCUIT) ON A CABLE As mentioned previously, it is possible to find the distance at which a transmission line is strongly mismatched (up to the case of either a shortcircuit or an open circuit).
  • Page 15 UNAOHM Figura 6 Connections for distance to fault calculation Figure 6 legenda: -Misuratore di campo = field strength meter (FSM) NOTE the maximum cable length which may be measured depends on the attenuation itself; if for example the cable has 20 dB attenuation for 100 meters, possible mismatch will not provoke substantial standing waves.
  • Page 16 UNAOHM For example, once having measured a ΔF of 30 MHz as in figure 6B and having noted that the cable is of the PEE type, it may be established that the open circuit (or shortcircuit) is at a distance of 4 meters from the point of measurement.

  • Page 17: Appendix - Thermal Noise

    UNAOHM 8. APPENDIX – THERMAL NOISE All electronic components, both passive and active, generate a signal caused by the thermal agitation of the electrons that are freed from their respective atoms and move without restraint in the conductor. The free electrons are in constant and chaotic motion among the practically still atoms in the metal.
  • Page 18 UNAOHM On a practical level, the noise spectrum is always limited by the bandwidth of the device in which it is generated or through which it transits. With respect to the result, this is equivalent to filtering the noise voltage from the start, picking up only the one that crosses the device with the B bandwidth.
  • Page 19 UNAOHM If the circuit, as is usually the case, is closed on the typical impedance which is the same as that of 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”...

  • Page 20: Warranty

    UNAOHM 9. WARRANTY This UNAOHM instrument is guaranteed against defects in workmanship and materials for a period of one year. Any necessary adjustments or repairs will be provided from our works where the instrument is to be delivered packed in adeguate packing AFTER an authorization for return has been received.

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