Introduction The 2026 is a multisource signal generator offering as standard two signal sources in one instrument. Up to three sources may be fitted, each of which is a fully functional modulated signal generator. Each source can either be routed to its own individual RF output or switched to the input of an RF combiner network before being fed to a separate combined RF output. All sources cover the frequency range 10 kHz to 2.4 GHz. An additional RF input is provided to enable the output from an external RF signal generator to be combined with the signals from up to two internal sources. Each signal source can be controlled independently in frequency and level, and each has its own amplitude, frequency, phase, FSK and pulse modulation capability. All parameters can be entered from the front-panel keyboard and a rotary control can be used to adjust most settings. The instrument includes a GPIB interface which allows remote control of all standard signal generator functions except the supply switch. The instrument is provided with built-in tests specifically for use with two or three combined sources such as for amplifier and receiver intermodulation tests and receiver selectivity tests. The sources may be locked together, offset in frequency (additionally with a harmonic or sub-harmonic relationship) as well as level. Microprocessor control ensures that the instrument is flexible and easy to use and allows programming by the General Purpose Interface Bus (GPIB) or RS-232 serial bus. The GPIB is designed to IEEE Standard 488.2 and is a means of sending commands to an instrument, via a data bus, from a remote controller or personal computer. The instrument can therefore be used manually or as part of a fully automated test system. Main features Operation Selection of parameters on the screen may involve one or more of the numeric, hard or menu selection keys or the rotary control knob. Parameters may be set to specific values by numeric key entry, while values may be varied in steps of any size using the [ ^ ][ ΰ ] keys or altered by moving the control knob, set to a particular sensitivity. Display The display is a dot matrix liquid crystal panel, with backlighting. Display contrast and brightness may be varied to accommodate differing lighting conditions and the setting saved in memory. Frequency selection Carrier frequency is either selected directly via the keyboard or remotely via the interfaces. Frequency resolution is 1 Hz across the complete frequency range of 10 kHz to 2.4 GHz. A series of carrier frequencies can be stored in non-volatile memory for recall when required. Output Peak RF output levels from each signal source of up to +24 dBm can be set up to 1.2 GHz (+20 dBm up to 2.4 GHz) by direct keyboard entry with a resolution of 0.1 dB down to -137 dBm. The peak output level from the combiner is +4 dBm up to 1.2 GHz (0 dBm up to 2.4 GHz). RF ON/OFF keys are provided to disable each individual output as well as the combined output. A choice of level units is available to the user and provision is made for the conversion of units (for example, dBm to μΥ) by a simple keypress. An electronic trip protects each independent signal source output against reverse power of up to 50 W. This prevents damage to output circuits when RF transmitter or DC power supply is accidentally applied to an RF OUTPUT connector. To facilitate testing of receiver squelch systems, an attenuator hold function allows control of the RF output without introducing RF level drop-outs from the step attenuator. Modulation Comprehensive amplitude, frequency and phase modulations are available. Pulse modulation can be applied to the carrier from an external pulse source. The instrument also produces FSK modulated outputs. An internal modulation oscillator is provided, having a frequency range of 0.01 Hz to 20 kHz. Sine, triangle and square waveforms are available. The oscillator is capable of generating one or two modulation tones simultaneously in one modulation channel. A BNC connector on the front panel offers access to the internal LF signal as well as providing an input for external modulation signals to be combined with the internal signals. These sources can be combined to give a number of modulation modes. The pulse modulation can be used in combination with the other forms of modulation. The frequency modulation range provides a 1 dB bandwidth of typically 100 kHz and provides FM deviation of 0 to 100 kHz. AC or DC coupled FM can be selected. Phase modulation is provided with a 3 dB bandwidth of 10 kHz and deviation range of 0 to 10 radians. Amplitude modulation with a 1 dB bandwidth of typically 30 kHz and with modulation depths of up to 99.9% is available with a resolution of 0.1%. Pulse modulation is available as standard with typical rise and fall times of less than 10 μs and 40 dB on/off ratio. The instrument also accepts one or two logic level inputs to produce a 2-level or 4-level FSK modulated output. The required FM deviation is set by keyboard entry. The external input voltage required for specified modulation is 1 Υ RMS (1.414 Υ peak). To accommodate other signal levels, Automatic Level Control (ALC) can be selected which provides correctly calibrated modulation for inputs between 0.75 and 1.25 Υ RMS. A modulation ON/OFF soft key simplifies the testing of signal-to noise-ratio. Incrementing All major parameters can be incremented or decremented in step sizes entered via keyboard entry or remotely. If no step size is entered for a parameter, the steps are preset to 1 kHz for carrier frequency, 1 kHz for modulation oscillator, 1 kHz for FM deviation, 0.1% for AM depth, 0.01 rad for ΦM and 1 dB for output level. In addition, the rotary control knob can be used to vary the parameter with the sensitivity of the knob being changed by means of the [x 10] and [^10] keys. Control knob operation can be assigned for the adjustment of one parameter, while another parameter is adjusted by the increment and decrement keys. By this means two parameters, for example carrier frequency and RF level, can be adjusted simultaneously. Frequency sweep The sweep capability of the instrument allows comprehensive testing of systems. Four parameters are used to specify sweep; start, stop, step size and time per step, all of which may be specified by the user. The sweep can be paused at any time and the frequency and level manually altered. During the sweep the RF level can be altered using the rotary control. Sweep triggering can be single shot or continuous and can be initiated directly or on the detection of a trigger. The triggering signal may either be programmed or from a TTL signal applied to the rear-panel TRIGGER 1 input. When frequency coupling is enabled, the coupled sources will track with the swept source. Memory The instrument provides both non-volatile and volatile memory for storing instrument settings. The non-volatile memory provides 100 full instrument settings and 100 settings of carrier frequency only. The volatile memory (RAM) also provides 100 instrument settings. Any one of the non-volatile instrument settings can be selected as the power-up setting for the instrument. Software protection To prevent accidental interference with the contents of internal memories, internal data is protected. Programming A GPIB interface is fitted so that all functions are controllable via the interface bus which is designed to the IEEE Standard 488.2. The instrument can function both as talker and listener. The instrument also has an RS-232 interface which uses the common GPIB command set to control the instrument and also allow new software upgrades or applications to be downloaded into the instrument. Calibration data All alignment data is digitally derived. Realignment can be undertaken, without removing covers, by protected front-panel functions or via the GPIB interface. Spectral purity With an SSB phase noise performance of typically -121 dBc/Hz at 20 kHz offset from a 1 GHz carrier, these instruments can be used for both in-channel and adjacent channel receiver measurements. Harmonically-related signals and non-harmonics are typically better than -30 dBc and -60 dBc respectively. Calibration This instrument has a recommended two-year calibration interval after which it should be returned for recalibration (for addresses refer to ‘International Service Centers’ section at end of manual).