Signal Generators 2018A and 2019A are synthesized generators similar except for their frequency range— 80 kHz to 520 MHz and 80 kHz to 1040 MHz respectively. Microprocessor control provides simple and rapid operation by direct keyboard entry of settings and the non-volatile memory, which can store up to one hundred settings, further reduces measurement time. Optional GPIB programmability extends the range of applications to include use in automatic test systems.
The excellent overall performance and wide range of facilities provided ensure that the generators have many uses in development, production and maintenance areas and for military applications. These features are further enhanced in four variant models.
Selection of carrier frequency is accomplished by direct entry via the keyboard or over the General Purpose Interface Bus (GPIB), with indication by an 8 digit liquid crystal display and units annunciators. Frequency resolution is 10 Hz up to 520 MHz, and 20 Hz above 520 MHz. Carrier frequencies can be stored in the non-volatile memory with immediate recall when required. A CARRIER ON-OFF switch is provided to completely disable the output. Provision is made for operation with an external reference frequency of 1 MHz or 10 MHz as required.
Selection of frequencies above the upper limit of each Generator is inhibited, but carrier frequencies below 80 kHz can be set with a warning appearing on the display. The generators are usable down to 30 kHz with minimal degradation of performance. One of the variant options provides a lower carrier frequency limit of 10 kHz for tests on l.f. communications equipment.
An incrementing facility permits stepping of carrier frequency in precisely defined increments of any size with an indication of total shift by use of the TOTAL SHIFT key and with provision for instant return to the starting frequency.
RF output levels up to 2 V e.m.f. ( + 13 dBm) can be set by direct keyboard entry or via the GPIB, with resolution of at least 0.1 dB over the entire range and a total accuracy of ± 1 dB from 80 kHz to 520 MHz and ±2 dB above 520 MHz. Levels are indicated on a four-digit liquid crystal display with units annunciators. Output levels can be incremented in steps of any size and up to twenty level settings can be stored in the memory.
A choice of nine calibration units is available to the operator and provision is made for the simple conversion of units (e.g. dBm to μ\/). Calibration data for the output level is held in the memory and may be altered from the front panel using a protected key sequence or over the Interface bus.
The output level can be offset by up to ±2 dB from the calibrated value to compensate for cable or switching losses external to the Generator. The operator may also use this facility as a means of deliberately offsetting the output level to ensure that all generators in an area give identical measurements. While using the offsetting facility the main calibration of the Generator is not lost and may be returned to at any time.
Comprehensive a.m., f.m. and Oscillator is included to facilitate frequency response measurements. A frontpanel socket provides a variable level output from the a.f. Oscillator.
The wide range frequency modulation provides f.m. deviation up to 5.2 MHz for 2018A and up to 10.4 MHz
for 2019A. Excellent f.m. accuracy is ensured by the storage of calibration values in the memory. Phase modulation is available with a deviation range of up to 520 radians for 2018A and up to 1040 radians for 2019A. Amplitude modulation is provided up to 99% depth. Modulation settings can be stored in the memory for recall when required. It is also possible to increment the deviation and depth settings.
External modulation is possible with a wide band input of 50 Hz to 100 kHz for f.m., 50 Hz to 10 kHz for p.m. and 20 Hz to 50 kHz (d.c. coupled) for a.m. A modulation levelling function is included which can be disabled when not required. HI and LO lights are provided as an aid to maintain calibrated modulation. They are extinguished when the input level is in the range 1 V ± 5%.
An auxiliary f.m. input is provided to allow a low level modulation signal to be mixed with either internal or external modulation. This facility is provided to allow sub-audible tones to be applied with standard modulation when testing military or commercial radio receivers which require such tones to lift the squelch.
Enhancements offered by the variants provide pulse modulation, improved a.m. and extended f.m. bandwidth. Pulse modulation is intended for use in the testing of radar systems, and improved a.m. for testing avionics equipment. The extended f.m. bandwidth variant is ideal for stereo broadcast measurements and tests on mobile radio equipment fitted with digital signalling circuits.
All parameters can be incremented or decremented in steps of any size, which may be simply entered via the keyboard of GPIB. If no step size is entered for a parameter the steps are pre-set to 1 kHz for carrier frequency, 1 kHz for f.m. deviation, 1 radian for p.m. deviation, 1% for a.m. depth and 1 dB for output level.
A single tap on either the UP or DOWN key moves the parameter by one step. If the key is held down the parameter steps once, waits one second and then moves at three steps per second. For search purposes it is possible to reverse this stepping direction without the one second delay.
Operation of the TOTAL SHIFT key displays the variations in all parameters from their original settings. Use of the RETURN key sets the selected parameter back to its start value.