Radio Communications Test Set type 2955B combines ail the measurement facilities required for testing mobile radio transceivers in the range up to 1000 MHz. it is a compact self-contained unit designed for bench or mobile use and can be considered as a combination of the following instruments:- RF frequency meter. AF frequency meter. RF signal generator. AF generators (two). RF power meter. AF and DC voltmeter. Modulation meter. AF distortion, S/N or SIN AD meter. Digital storage oscilloscope. Sequential tones decoder and encoder. DTMF decoder and encoder. DCS decoder and encoder. POCSAG radio pager encoder Push-button selection makes all the necessary interconnections for each measurement, eliminating the need for the many interconnections required when separate instruments are used. Function selection and data entries are made on a colour-coded keyboard with the operating sequence logically arranged from left to right. Instrument operation is greatly facilitated by means of CRT displays which provide prompts during data entry and guidance during operating sequences while also showing the instrument settings and the measurement results. The measurement results are displayed by digital readouts and also by either autoranging bar charts or by a storage oscilloscope which has repetitive sweep, single shot and freeze facilities. Frequency meters. As there are two frequency counters, simultaneous AF and RF frequency readings can be displayed. Ranges and resolutions are respectively from 20 Hz to 20 kHz at 0.1 or 1 Hz and from 1.5 to 1000 MHz at 1 or 10 Hz. Either an internal or an external frequency standard can be used. Signal generator. The signal generator can be amplitude, frequency, or phase modulated, internally or externally, the internal modulating signal being obtained from the AF generators. Amplitude modulation is variable up to 99% for carrier frequencies from 0.4 to 500 MHz. FM deviation can be set from 0 to 25 kHz and ΦΜ deviation from 0 to 10 radians. Transmitter and receiver RF signals use N and BNC connectors which are selected by means of a key. Reverse power overload is indicated by a visual warning and an audible alarm. When a reverse power overload is applied to the BNC socket, an automatic trip circuit operates* Modulation meter. Automatic frequency tuning and levelling of the modulation monitor provide accurate measurements of AM, FM and ΦΜ. Because of the independent tuning, modulation measurements can be made on duplex systems. The modulation can be observed on an oscilloscope and its symmetry checked from the peak and trough values displayed on a dual bar chart. The demodulated output is available at a rear panel socket. Provision is made for audible monitoring using the built-in loudspeaker or by an external loudspeaker or headphones. RF power meter. The absorption RF power meter measures up to 75 W continuously or up to 150 W for short periods over a frequency range of 1.5 to 1000 MHz. The connection of the RF Directional Power Head (available as an optional accessory) extends the capability of the instrument by enabling measurements of forward power, reverse power and VSWR to be made. AF generators. The two AF generators provide a range of frequencies from 10 Hz to 20 kHz for single-tone or two-tone testing. The audio output is available at a front panel socket and the generators also provide the internal AM, FM and ΦΜ for the RF signal generator. A combined 600 Ω Balanced to Unbalanced Convertor and 20 dB Attenuator is available as an optional accessory. AF voltmeter. Operating in the range 20 Hz to 20 kHz, the true RMS voltmeter has f provisions for measuring AF or AF plus the DC component. Band-pass and low-pass filters can be selected. Distortion, S/N (signal to noise) or S1NAD (signal to noise and distortion) meter. The AF distortion meter operates at 1 kHz which is supplied by one of the AF generators. The bar chart displays are autoranged at 10% and 30% (for distortion), at 30 and 100 dB (for S/N) or at 18 and 50 dB (for SINAD). The Psophometric Filter Units (available as optional accessories) enable ССГГТ and С-message weighted measurements to be made. Sequentia! tones decoder and encoder. For testing selective calling tones encoding and decoding equipment, the instrument is capable of receiving and generating five defined tone frequency standards plus a user-defined standard. Provision is made to receive and to send sequences of up to 33 tone frequencies. For transmitter testing, each received tone is compared with the standard frequency allocations which is held in memory and, if it is within the limits, its tone number and % frequency error are displayed. For receiver testing, the tones can be generated in single step, tone burst or continuous cycle. There is a revertive tones facility whereby tones are sent to a receiver and the the answering sequence is decoded. DTMF decoder and encoder. There are similar facilities for testing DTMF encoding and decoding equipment. DCS decoder and encoder, There are similar facilities for DCS encoding and decoding equipment. POCSAG radio pager encoder. The instrument can be used to check the response of a pager to an RF signal modulated with the pager’s address and an appropriate message. Deliberate errors can be created in the outgoing signal. GPIB interface Unit. This unit allows the instrument to form part of an automatic test system. Displays can be configured to the user’s own requirements using a comprehensive character set. With this unit, a 24 Column Printer (available as an optional accessory) can be used. Serial Interface Unit. This unit allows the instrument to be controlled by a personal computer using the EIA-232 (formerly RS-232) standard. Displays can be configured to the user’s own requirements using a comprehensive character set. Off-air receiver. In the Option 1 only, there is a sensitive receiver which allows off-air monitoring of transmitters. Calibration and testing. Routine calibration has been kept to a minimum. Calibration factors are stored in a non-volatile memory and can be accessed with a secure access code from the front panel keys or by the GPIB, permitting rapid recalibration. A built-in self test facility can be called up whenever it is required. This enables faults to be identified to major module level or to groups of components.