2.1 INTRODUCTION 2.1.1 The Racal-Dana signal generator Model 9087 is designed primarily for the testing of communication equipment over the frequency range from 10 kHz to 1.3 GHz. The RF output is phase-locked to the frequency standard, the wide frequency range being obtained by the use of a multi loop synthesizer. The instrument is microprocessor controlled, and combines versatility with ease-of-control. 2.2 RF TUNING 2.2.1 Tuning may be effected in one of five ways. These are: (a) Numeric keyboard. The required frequency is set directly. (b) Step-up and step-down keys. The displayed frequency is changed in steps. The step size may be one of three preset values, or an operator-set value. (c) Spinwheel. The displayed frequency changes in steps as the spinwheel is rotated. Again, the step size may be one of three preset values or an operator-set value. The use of the spinwheel, particularly with a small step size, affords all the advantages of analog tuning while retaining the stability of a synthesized system. A HOLD control is provided to isolate the spinwheel to prevent accidental changing of the frequency set. (d) GPIB. An internal interface is fitted. (e) Direct frequency access (DFA). The required frequency may be set by applying suitable control signals directly to the microprocessor data bus to a rear-panel socket. The use of this method permits extremely rapid changes of frequency to be made. A special interface is required. Full details may be obtained from Racal-Dana Instruments. 2.2.2. The frequency set is displayed on a 10-digit, dot-matrix LED display, affording 1-Hz resolution throughout the frequency range of the instrument. The decimal point is fixed, and leading zeros are suppressed. 2.3 FREQUENCY SWEEP 2.3.1 The 9087 incorporates a frequency-sweep facility which permits the output frequency to be swept, in steps, between two operator-selectable frequencies. The step size can be selected by the operator, and four preset step rates are available. 2.4 RF OUTPUT 2.4.1 Automatic levelling maintains the output level within ±0.4 dB for output frequencies up to 650 MHz, and within ±1.0 dB for output frequencies in the range from 650 MHz to 1.3 GHz, relative to the 50 MHz level. 2.4.2 The output-level range is from +19 dBm to -140 dBm into 50 Ω. The level may be set by means of a numeric keyboard, or the set value may be stepped up or down using either the step keys or the spinwheel. The step size may be one of three preset values, or an operator-set value. 2.5 MODULATION FACILITIES 2.5.1 Amplitude, pulse, frequency, and phase modulation facilities are provided. Two internal-modulating frequencies, locked to the frequency standard, are provided, and external-modulating sources may also be used. Details of the permissible range of modulating frequencies, and of the modulation depths and peak deviations which can be obtained, are to be found in Section 1 of this manual. 2.5.2 Amplitude or pulse modulation may be applied simultaneously with frequency or phase modulation. Either or both of the internal-modulating sources, or a combination of internal and external sources may be used. 2.6 FR0NT-PANEL SETTING STORAGE 2.6.1 A non-volatile memory allows the storage of up to 33 (100, if the 100- location memory option is fitted) complete sets of front-panel control settings. These may then be recalled when required. The recalled data may be implemented immediately, or may be displayed for checking before the instrument output is reset. This facility allows the contents of the store to be examined without affecting the output of the instrument. 2.6.2 An exchange facility allows the contents of any two store locations to be exchanged without affecting the output of the instrument. 2.6.3 On switching off, the current front-panel control settings are stored automatically. On switching on again, these settings are immediately implemented. An initialization program is also provided to set the instrument to a known state. 2.7 ERROR INDICATIONS 2.7.1 Certain errors in the operation of the instrument will result in the flashing of a LED-error indicator and the generation of a service request (SRQ) via the GPIB interface. The errors which can be detected are each given a two-digit code, which can be displayed. The nature of the error can then be established by reference to the pull-out information card beneath the instrument or to Section 4 of this manual. 2.8 DIAGNOSTIC CHECKS 2.8.1 Several points in the instrument's circuits are monitored for possible malfunction. The detection of a fault is indicated by the generation of an error indication. A digit in the numeric displays will flash to indicate the location of the fault. 2.8.2 In the event of overheating, the instrument is switched automatically to the standby condition, with only the frequency standard and the microprocessor system active. 2.9 SPECIAL FUNCTIONS 2.9.1 A number of special functions are available to the operator. Details are given in Section 4 of this manual. 2.10 OUTPUT PROTECTION 2.10.1 The RF output will withstand the accidental application of reverse-RF power at levels up to 1 W. 2.10.2 Protection against reverse powers of up to 50 W is given by the internally mounted, reverse-power-protection-unit option. This isolates the RF output socket, and sounds an audible alarm, when reverse powers are applied above the threshold level. The device latches in the tripped state. 2.11 GPIB INTERFACE 2.11.1 An internally mounted interface to the IEEE-488-GPIB is provided. This enables all the instrument functions, except the line power switching and frequency standard changeover, to be remotely controlled. An adapter to provide compatibility with the IEC 625-1 bus is available as an optional accessory. 2.11.2 Control via the GPIB may be exercised in one of three ways. These are: (a) Immediate Mode Control, in which each data byte accepted by the 9087 from the bus is processed before the next byte is accepted. This provides the shortest delay in completing the resetting of the 9087's output following a data entry made on a controller keyboard. (b) Deferred Mode Control, in which the complete data string is accepted from the bus and stored before processing is commenced. The use of the bus is therefore limited to the data transfer time, and better utilization of the bus is possible at the cost of a small increase in the total time taken to vary the 9087's output parameters. (c) Learn Mode Control, in which data strings related to particular settings of the 9087's output are generated in the 9087 and stored in an external memory. When a data string is fed back to the 9087 as an addressed command, the output parameters will be set to the related values. This provides a significant saving in time when compared with keyboard control, and, by feeding back a succession of data strings, the 9087 may be stepped rapidly through a number of different output-parameter patterns. Two lengths of data string are available, the longer controlling the full range of output parameters and the other controlling frequency only. The longer data string may also be used to monitor the instrument's settings. This may be found useful when the 9087 is used in operator-interactive systems.