Radio Communications Test Set 2955A provides comprehensive test facilities for AM, FM and ΦΜ mobile radio transceivers operating up to 1000 MHz. The 2955A is a combination of the following instruments:- RF power meter. DC and AF voltmeter. RF counter. AF counter. RF generator. AF generators (two). Modulation meter. AF distortion meter. S/N and SINAD meter. Sequential tones decoder and encoder. DTMF decoder and encoder. DCS decoder and encoder. POCSAG radio pager encoder. Digital oscilloscope. These are automatically connected to the appropriate socket w'hen an operating mode is selected. A large CRT display shows all the generated and measured information for each test and a direct indication of the control settings being used. The 2955A can be used to check a wide range of equipment including simplex and duplex radio telephones and mobiles using selective calling and cross-band repeaters. 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. Radio Communications Test Set type 2955R is identical to the 2955A except that the 2955R also contains a sensitive receiver for off-air monitor testing of transmitters. 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 <£M 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 <i>M. 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 20 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 <I>M for the RF signal generator. A combined 600 £2 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 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 SINAD (signal to noise and distortion) meter. The AF distortion and noise 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 CCITT and C-message weighted measurements to be made. Sequential 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 testihg, 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. The GPIB additionally enables a display to be configured to the user’s own requirements using a comprehensive character set. The GPIB also enables the 24 Column Printer (available as an optional accessory) to be used.