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LOCAL OPERATION
3-36
*DUPLEX*
All of the above information relating to modulation characteristics and frequency response testing
also applies to tests made using the Dx TEST mode. The oscilloscope facility is not available
when in Dx TEST mode.
Modulation distortion
C1640
dBdB
dB dB
kHzkHz
kHz kHz
a
cd
b
FrequencyFrequency
Frequency Frequency
11
1 1
Filter Response
Noise
Noise Noise
Distortion Products
Distortion Products
Signal
Filter Response
Fig. 3-10 Distortion level and signal to noise level measurements
The signal containing the information being communicated will become distorted during its
progress through the system. This distortion may be very slight and almost unnoticeable to the ear
or it may be so severe as to cause the information to become unintelligible.
The reasons for this distortion to the signal are the non-linearity of the amplifiers and modulators
in the system, and noise within the circuits becoming attached to the signal.
By applying a sinewave signal of known purity to the input of the system and measuring the
distortion and noise levels of the demodulated signal obtained at the output of the system,
evaluation of the quality of the transmitter is possible.
The three measurements used for this evaluation are SINAD level; distortion percentage; and
signal to noise ratio.
The procedures described below are carried out repeatedly under the instruction of the Service
Monitor software and the displayed results are continually updated.
To obtain the SINAD level of a signal at the output of a transmitter the output level is measured
and noted.
The signal measured consists of the value of the fundamental signal, the values of any distortion
products generated and the value of any noise present.
A notch filter tuned to the frequency of the input signal is then placed in the output signal path and
the level again measured and noted. The second measurement consists only of the values of any
distortion products generated and the value of any noise present. See page 3-36, Fig. 3-10 a, b, &
c, Distortion level and signal to noise level measurements.
- Operating Manual 1
- COMMUNICATIONS 2
- SERVICE MONITOR 2
- About this manual 3
- Associated publications 4
- Contents 5
- Fusibles 10
- Vorsichtsmassnahmen 12
- Sicherungen 13
- Eignung für Gebrauch 14
- Precauzioni 15
- Fusibili 16
- Caratteristiche d’uso 17
- Precauciones 18
- Idoneidad de uso 20
- Chapter 1 21
- GENERAL INFORMATION 21
- Purpose and features 22
- Transmitter testing 23
- Receiver testing 24
- Duplex testing 24
- Systems testing 25
- Service Monitor 26
- Amplifier 26
- Performance data 27
- Audio analyzer 29
- Transmitter measurements 31
- Audio generators 34
- Cellular and trunking 35
- Frequency standard 35
- General features 36
- Options and accessories 37
- EC Declaration of Conformity 41
- Chapter 2 42
- INSTALLATION 42
- Ventilation 43
- Power requirements 44
- Class I power cords (3-core) 44
- British 45
- North American 45
- Continental Europe 45
- Connecting to a DC supply 47
- RF and AF connections 47
- Hot Surfaces 47
- Accessory socket connections 48
- Remote control connections 49
- 9-WAY 9-WAY 50
- 9-WAY 25-WAY 50
- Self tests 51
- Routine maintenance 52
- 1. Visual inspection 53
- 2. Earth bonding tests 53
- 3. Insulation tests 54
- 4. Rectification 54
- Cleaning 54
- Chapter 3 55
- List of tables 56
- List of figures 57
- About this chapter 57
- Front panel layout 58
- Hot surfaces 60
- 27282920 62
- Getting started 63
- Test mode screens and menus 63
- HELP/SETUP 64
- Volts, dBm, dBV or Watts and 67
- Bar charts 69
- Using the test modes 70
- Connections 73
- Tx power 76
- Audio frequency filtering 78
- Audio distortion measurement 78
- Audio generator setup 80
- TRANSIENT ANALYSIS 83
- 50 % will place the trigger 84
- Transmitter frequency 85
- Display time scale 85
- Pre-trigger 85
- External attenuators 88
- Modulation characteristics 89
- Companding/limiting 89
- *STANDARD OSCILLOSCOPE* 89
- *EXPANDED OSCILLOSCOPE* 89
- *DUPLEX* 90
- Modulation distortion 90
- Rx test (receiver testing) 93
- AF input level measurement 99
- Making measurements 101
- AF bandwidth 103
- AF distortion 103
- Selectivity 104
- Spurious response 105
- AGC response 106
- Dx test (duplex testing) 107
- LOCAL OPERATION 108
- Systems 109
- Spectrum analyzer 109
- Overview 110
- Setting up 110
- Start frequency 111
- Stop frequency 111
- Peak find 111
- Resolution bandwidth 111
- Reference level 111
- Vertical scale 112
- Markers 112
- Tracking generator facility 113
- Centre at the 114
- Demod settings 115
- mode is the same as for the 116
- Input level measurement 118
- Input filtering 119
- Distortion measurement 119
- *Oscilloscope* 121
- Incremental adjustment keys 122
- Assigning 123
- Tones sub-mode 124
- Signal routing 125
- RF input attenuators 125
- Sequential tones 126
- Tone Generate Mode 128
- Tone ON/OFF control 129
- Revertive tones 130
- Output level 131
- Tone selection 131
- Tone frequency shift 131
- DCS receiver decoder testing 133
- Tx test DTMF tones function 135
- Rx test DTMF tones function 136
- Dx test DTMF tones function 137
- AF test DTMF tones function 137
- Tones ON/OFF control 137
- AF Tone Remote 138
- Testing a radio pager 141
- Decoding POCSAG type signals 142
- Oscilloscope 143
- Expanded display 144
- Stores, settings/results 145
- Storing 146
- DISPLAY HOLD STORE 146
- Other memory functions 146
- Titling store locations 147
- Memory card 148
- Write-protecting cards 149
- Coded store protection 149
- Storing on memory cards 150
- Printing from memory cards 151
- Error messages 152
- Real time clock 153
- Date and time stamping 153
- Printer 154
- Rear accessory 155
- LOCAL OPERATION 158
- Chapter 4 172
- TECHNICAL DESCRIPTION 172
- Power supply 173
- The display 174
- TECHNICAL DESCRIPTION 175
- Tx test mode 176
- Data generator 177
- Receiver circuits 178
- IF circuits 179
- Demodulators 180
- RF counter 181
- Measurement ranging circuits 181
- Distortion/SINAD filter 181
- Oscilloscope function 181
- Rx test mode 182
- RF oscillator 182
- Dx test mode 185
- Spectrum analyzer mode 185
- AF test mode 185
- Systems mode 186
- Chapter 5 187
- ACCEPTANCE TESTING 187
- Introduction 188
- Test equipment 189
- RF output tests 190
- ⎭ ⎩ 191
- RF output level 192
- BNC output mode 193
- Attenuator accuracy 193
- Spectral purity 195
- Signal generator 196
- Modulation meter 196
- Amplitude modulation 197
- Frequency modulation 198
- AF output tests 199
- Audio generator distortion 200
- Audio generator frequency 201
- AF input tests 202
- Audio voltmeter 203
- Specification 204
- RF input tests 205
- Splitter 206
- Modulation analyzer - AM 208
- RF frequency meter 210
- RF spectrum analyzer 212
- RF broadband power meter 214
- Signalling systems 215
- Appendix A 229
- DIRECTIONAL POWER HEADS 229
- Precautions 230
- Précautions 231
- Vorsichtsmaßnahmen 232
- Features 235
- Power measurement 238
- MAX SAFE POWER 239
- Supplied 241
- Optional 241
- General 242
- Procedure 242
- Technical description 244
- Appendix B 246
- AVIONICS SYSTEM 246
- Avionics system overview 247
- Glideslope signal 248
- Marker beacons 249
- The simulated VOR signal 250
- The simulated SELCAL signal 251
- Avionics system operation 252
- RF frequency and level 253
- Setting the RF level 254
- Using the [DDM] key 254
- Marker beacon 255
- Using the VOR Ident facility 257
- AEROFLEX INTERNATIONAL LTD 263
- 48000/025 Issue 1 264
- November 2005 265
Verwandte Produkte und Handbücher für Fernseher & Monitore Aeroflex 2948B
(8 Seiten)
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