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60 MHz Coaxial Cable System for 10800 Channels Per-Alrik Hallberg, Thorwald Lundmark and Luigi Manes By extending the band transmitted over coaxial cables to 4-60 MHz it is possible to transmit 10800 channels, in the form of twelve supermastergroups or six television channels. LM Ericsson in collaboration with the Italian company FATME, which is a member of the Ericsson Group, have developed a 60 MHz system for coaxial cables, ZAX 10800. The equipment is manufactured in the same construction practice as the 4 MHz and 12 MHZ coaxial cable systems. The article gives a description of the equipment and also the result of a field trial in Italy. with six tubes is 32 400 channels and the capacity of a cable with twelve tubes is 64 800 channels. This is a very considerable capacity, which it is rarely desirable to exceed, among other reasons because of the consequences of a cable break. In the case of coaxial cable of small diameter, however, the repeater distance will be very short which means more noise than is desirable. UDC621 315212 Fig. 1 Equipment for sending and receiving in the line terminal COM Combiner FEQ Fixed equalizer PE Pre-emphasis network PEQ Pre-equallzer LBO Line building-out network PC Pilot combiner PFU Remote power feeding unit FLO Fault location oscillator DE De-emphasis network EEG Echo equalizer SEP Separator The growth of the long-distance traffic creates a demand for greater traffic capacity. Since the cost of electronic equipment is only a fraction of the cost of cables, existing coaxial cables have naturally been utilized as far as is technically and practically possible. A limiting factor, however, is that the transmission data of the cable may deviate so much from the calculated data that it is difficult to obtain sufficiently accurate attenuation equalization. Most existing coaxial cables of normal diameter are suitable for transmission of 60 MHz and the cost per channel kilometre is low even in the case of new cables because of the high transmission capacity. The balance between cable cost and repeater cost is better than in the case of other 4-wire coaxial systems. The transmission capacity of a cable The 60 MHz coaxial cable system for 10800 channels, ZAX 10800, consists of terminal equipment and line repeaters. The system is in the LM Ericsson tradition in this field as regards reliability, maintainability and mechanical construction practice. The terminal equipment is described first, then the different types of line repeaters and the power feeding equipment, followed by regulation, equalization and fault location. The mechanical construction is described briefly and finally the results from a trial route are presented. Terminal equipment The function of the terminal equipment is to adapt the line band from the multiplex equipment to what is needed for transmission over the line, see fig. 1.
PER-ALRIK HALLBERG THORWALD LUNDMARK Transmission Division Telefonaktiebolaget LM Ericsson LUIGI MANES FATME, Rome Fig. 2 Line repeater with fixed gain Fig. 3 The basic design of the pre-amplifier. In a regulating line repeater a thermistor T is used and in a non-regulating repeater a resistor R that corresponds to a certain gain. RN is a regulating network. Fig. 4 The basic design of the power amplifier Send direction On the send side the necessary regulating pilots 61160, 22372 and 4287 kHz are added and the upper part of the band is pre-emphasized. It may also be necessary to include stop filters to suppress disturbances in the line band at the pilot frequencies, The frequency comparison pilot 4200 kHz can be fed into the equipment at a level of 0 dBm or -7 dBm. It is fed in together with the other pilots. The fault location frequencies are generated, with a unique frequency for each line repeater, and are supervised at the receiving terminal. The received frequencies can be loop connected at one of the terminals so that all supervision can be carried out from the other terminal. The attenuation in the send side station cable can be equalized by up to 3.5 dB in an active equalizer, which corresponds to a line length of approximately 30 m at 60 MHz. The equalizer is also equipped with two similar inputs, so that measurements can be carried out with additional measuring frequencies during traffic. A corresponding facility is provided at the output in the receive direction. Receive direction The main task of the receive side is to equalize and regulate the received line band. This is done with the aid of fixed equalizers, an echo equalizer and regulation equipment related to the two extra pilots 22372 and 4287 kHz. Regulation with the aid of the main pilot 61160 kHz takes place in the terminal repeater, where de-emphasis to flat (frequency independent) level also takes place. The pilots are suppressed by filters with 50 dB attenuation. The frequency comparison pilot 4200 kHz, which is only transmitted over the system and thus is not used for regulation purposes like the other pilots, is extracted in a flat amplifier and is fed to the frequency control equipment in the station. The flat amplifier also compensates for the basic loss of the passive stop filters, and feeds the fault location frequencies both to the loop connection and to a test point on the front of the unit, where they can be checked with the aid of an external instrument. Line repeaters The line repeater is available in three variants: one with fixed gain, one with pilot regulation and one for use in the terminal. All three have the same mechanical design and each is a compact unit that includes the equipment for both directions of transmission. Line repeater with fixed gain The simplest version of the line repeater has fixed gain. The main parts, fig. 2, for one direction are — amplifier — pre-equalizer — power separation filters — line building-out network and common for both directions are — zener diodes — fault location oscillator. The amplifier part consists of two 2- stage amplifiers: one pre-amplifier with low thermal noise and one power amplifier with fixed gain and very low harmonic distortion, figs. 3 and 4. Together they give a gain of 28.5 dB, which can be varied over the range ±3 dB, by changing a resistor in the feedback network. A transformer is placed between the two amplifiers in order to provide phase inversion in each line repeater. In this way a more favourable addition of the noise contributions from the individual repeaters is obtained 6 . Fig. 5 The principle tor power feeding the line repeaters. 31 -34 are the different connection points. Every other line repeater is changed over so that the feeding direction is always changed. This balances the power feeding relative to earth, which also leads to a reduction of the hum modulation.
Page 1: ERICSSON REVIEW 1 1978 OPERATIONAL
Page 5 and 6: ERICSSON REVIEW NUMBER 1 • 1978
Page 7 and 8: 3 STEN RIMBLEUS Stockholm Telecommu
Page 9 and 10: Fig. 4 (left) The operation and mai
Page 11 and 12: Types of faults, measures and subsc
Page 13 and 14: 9 ABDULLAH AL-SABEJ Chief Engineer
Page 15 and 16: Stored Program Controlled PABX, ASB
Page 17 and 18: 13 When the receiver is lifted the
Page 19 and 20: 15 five such matrices permit connec
Page 21 and 22: 17 Fig. 8 Printed board assembly fo
Page 23 and 24: Technical data Capacity Number of e
Page 25 and 26: 21 HENNING ANDERSEN VILLYK. PEDERSE
Page 27 and 28: 23 signalling was to be carried out
Page 29 and 30: 25 Fig. 10 Simplified block diagram
Page 31: Fig. 12 The principle for common tr
Page 35 and 36: 31 Fig. 9 Regulation range for the
Page 37 and 38: Fig. 12 Power feeding of the line r
Page 39 and 40: 35 oscillators also cease operating
Page 41 and 42: Technical data Electrical data Cabl
Page 43 and 44: 39 CHRISTOPHER LORENZ Financial Tim
Page 45 and 46: The Ericsson Group With associated

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