photo Philips SOZ 362 5 kW AM short-wave transmitter type SOZ 362

An AM short-wave broadcast transmitter having an output power of 5 kW and suitable for operation on any frequency in the 2.2-28 Mc/s range.


Philips' Telecommunicatie Industrie have over 40 years' experience in the manufacture of broadcasting transmitters. This experience, combined with a modern outlook and great inventiveness, results in products satisfying high international standards. The 5 kW channelised shortwave transmitter SOZ 362 is one of those products.

It meets the strictest requirements as to distortion and noise level and the greatest care has been devoted not only to performance and reliability but also to the outward appearance of the transmitter.

Unit construction

The RF unit, the modulator and the power supply unit are the basic units from which the transmitter is constructed.

Each unit is separate, complete in itself and housed in a steel cabinet of standardized dimensions. The number of RF units can be increased to a maximum of three per transmitter. In this way a change-over to another frequency can be made in a matter of seconds, thus making possible a considerable increase in the number of actual transmitting hours. An aerial relay supplied with each RF unit permits faultless automatic switching of the aerial.


The transmitter is equally suitable for local manual operation and remote-controlled operation.

The necessary controls are fitted on the front panel. Reliability is so great that maintenance of the transmitter consists merely in switching it on or off and taking a few meter readings. The remote control unit has to be ordered separately. The remote control relays, however, are included with the transmitter.


Prefabrication is employed on such a large scale that this 5 kW transmitter is very simple to install and can be installed quickly. A manual containing full instructions is supplied.

Prefabricated inter-unit wire forms are separately packed and can be placed between the cabinets in a very short time. All cables suplied are cut to length, provided the transmitter lay-out is decided upon before the equipment is shipped. All installation work can be carried out with the usually available tools; there are no special tools to buy.

With each transmitter a standard kit is supplied free of charge. These standard kits contain components such as fuses, pilot lamps, etc. In addition, some enamel is supplied to repair any superficial damage sustained in transit or during installation.


Neither maintenance nor installation requires special skill. The various components are specially arranged to make them easy of access; the RF and modulator units are fitted with telescopic runners, while the power supply unit has a front door and lift-off covers. The interlocking and switching relays of each unit are fitted on a fixed panel at the rear of the cabinet. Standard spare-part kits are available as optional extras. Full advantage can be taken of Philips' service facilities all over the world.


In construction, particular attention has been paid to efficiency and to use under conditions of tropical heat, extreme cold and considerable humidity. Each cabinet is fitted with drying lamps to prevent condensation occurring after the transmitter has been switched off. Only high-quality components are used in order to increase reliability.

The transmitter is equipped with the famous philips tetrodes, types QQE 06/40, QE 06/50 and QBL 5/3500. The useful life of these tubes is increased even further by conventional rating. The transmitter is smoothly finished, both at the front and at the rear. In addition, various protective circuits have been incorporated to guard staff and equipment from the consequences of operational errors. A safety-gate switch fitted on the door of the power supply section switches off all high tensions (4500 V, 800 V, 600 V) as soon as this door is opened. No voltage can be applied to the output tubes until they are being cooled. The transmitter is completely screened and produces no troublesome radiation.


Various methods of air-cooling are possible with this transmitter. If required, the blowers may be installed in an area quite separate from the actual transmitter room. This is not strictly necessary for noise prevention as the blowers used are of the low-noise type. The air is drawn in through oil bath filters and then taken through each RF and modulator unit under pressure. The resulting higher pressure in the cabinets keeps dust out. The heated air can be led out of the building or be used to heat the transmitter room.


The outward appearance of this robust transmitter is simple and well-proportioned, having been designed by a special department of the Philips concern. The pleasant appearance of the transmitter is further enhanced by a completely smooth finish and an attractive arrangement of the controls and meters over the transmitter front. For the same reasons the exciter unit is fitted behind a blank panel, which also protects it against accidental detuning.

The cabinets are finished in two-tone grey enamel, the front of the transmitter having dull chromium ornamental strips.

All doors have heavily chromium-plated handles.

The controls are normally labelled with English text, but labels can be provided in various other languages on request.

Flexibility of lay-out

The type SOZ 362 transmitter is extremely flexible and can be installed in rooms of various shapes and sizes. The larger separate components, such as the modulation choke, the modulation transformer, etc., can be set up either in a separate room (basement) or behind the transmitter proper. In the latter case, the side walls of the transmitter may be extended by means of matching panels, while a door in the side wall gives access to the compartment thus formed behind the transmitter. By means of blank panels the width of the transmitter can be increased to match its depth.

Circuit description

The transmitter can be fitted with up to three type SFE 287 RF units. The number used will depend on the number of frequencies required. The transmitter also comprises a type SFV 169 modulator and a type SFD 167 power supply unit, each housed in a separate cabinet.

Radio-frequency unit type SFE 287

The driver stage of this unit consists of an interchangeable type SFE 133 exciter unit. A selector switch enables this exciter unit to be used either with a crystal-controlled circuit or, in emergencies, with a self-oscillating circuit. There is a third possibility, when an external drive unit or a VFO with high frequency-stability, e.g. Philips' type SFE 249, is employed. This additional equipment has to be ordered separately.

The exciter unit comprises a two-stage amplifier whose push-pull output stage is equipped with the type QQE 06/40 twin tetrode. The exciter unit has a frequency range of 2.2-28 Mc/s, divided into 7 sub-ranges. The latter are covered by using different plug-in anode circuit coils in the oscillator and buffer stages.

The amplifier stage of the RF unit is equipped with two type QQE 06/40 twin tetrodes in a push-pull circuit. The anode circuit is capacitively coupled with the output stage. The latter stage contains two air-cooled type QBL 5/3500 tetrodes, operated under class C conditions in a push-pull circuit.

Cross-neutralization by means of two neutralizing capacitors is employed in the output stage. The 600-ohm feeder circuit is coupled with the anode circuit of the output stage by induction. Each RF unit is tuned to one specific frequency in the 2.2-28 Mc/s range. This range is divided into the following sub-ranges: 2.2-3.2 Mc/s, 3.2-4.7 Mc/s, 4.7-6.9 Mc/s, 6.9-10 Mc/s, 10-14.7 Mc/s, 14.7-21 Mc/s and 21-28 Mc/s.

The change-over to another frequency is effected within seconds by switching from one pre-tuned RF unit to another and this improves the efficiency of the transmitter considerably.

Modulator unit type SFV 169

The type SFV 169 modulation amplifier consists of three push-pull stages. The low-power circuit is a two-stage amplifier, the first stage being equipped with one and the second with two type QE 06/50 tetrodes. The two tetrodes of the second stage are connected in push-pull. This amplifier includes a network for maintaining a phase relation suited to the application of feedback. The voltage amplifier is followed by a zero-gain cathode follower stage, equipped with three type QE 06/50 tetrodes, which drives the grids of the two air-cooled type QBL 5/3500 modulator power tetrodes. Feedback is applied to the grids of the input voltages amplifier from the anode circuit in the output stage via a resistor-capacitor network having zero phase shift up to frequencies that are many times the highest modulating frequency.

The input impedance of the modulator unit is 600 ohms.

Power supply unit type SFD 167

The power supply unit comprises four different rectifier units, viz.:

a single-phase full-wave rectifier for -170 V DC, equipped with two type DCG 4/1000 G mercury-vapour rectifier tubes;

a three-phase half-wave rectifier for 600 V DC, equipped with three type DCG 4/1000 G mercury-vapour rectifier tubes;

a three-phase half-wave rectifier for 800 V DC, equipped with three type DCG 4/1000 G mercury-vapour rectifier tubes; and

a three-phase half-wave rectifier for 4500 V DC, equipped with three type DCG 5/5000 GB mercury-vapour rectifier tubes.

A common transformer, built into the power supply cabinet, is used for the 600 V and 800 V rectifiers. The power supply unit most be connected to a three-phase mains of 380 V, 50 or 60 c/s, with an earthed neutral conductor.

Frequency range 2.2-28 Mc/s in seven sub-ranges
Frequency tolerance 2.2-4 Mc/s: ± 20.10-6
4-28 Mc/s: ± 15.10-6
RF output (carrier) 5 kW rated
RF output impedance 600 ohms balanced (on special order 50 or 75 ohms unbalanced)
Standing wave ratio max. 1.4 : 1
Spurious radiation according to CCIR recommendations
AF input impedance nominal 600 ohms balanced
AF input level (reference 1000 c/s at 100% modulation) 0 dbm ± 2 db
(0dbm = 1 mW into 600 ohms)
Linear distortion (from 30 to 10,000 c/s, reference 1000 c/s at 60% modulation) within ± 1.5 db
Non-linear distortion (from 50 to 10,000 at 90% modulation) less than 3 %
Noise level (reference 1000 c/s at 100% modulation) better than -60 db (unweighted)
Modulation capability 100% instantaneously
60% continuously in the range 50-10,000 c/s
Carrier shift less than 5% up to a modulation depth of 95%
Power supply 3 x 380 V ±5%, 50 c/s or 60 c/s ±5%
four-wire mains (adaptation to other voltages is possible by use of an optional, separate autotransformer)
Power consumption (transmitter equipped with 1 RF unit) at 0% modulation: approx. 11 kW
at 30% modulation: approx. 13 kW
at 100% modulation: approx. 16 kW
at stand-by: approx. 2.5 kW
consumption per additional RF unit at stand-by: approx. 1.7 kW
Power factor approx. 0.82
Ambient temperatures at sea level: 10° to 45° C
at 6000 feet: 10° to 35° C
Relative humidity up to 95%
Dimensions (for a transmitter with one RF unit) height: approx. 84 in. (2120 mm)
width: approx. 64 in. (1620 mm)
depth: approx. 34 in. (870 mm)
Minimum floorspace: 120 x 140 in. (3000 x 3500 mm)
Weight (for a transmitter with one RF unit) approx. 4620 lb. (2100 kg)

RF stages AF stages and modulator Rectifiers
Number Type Number Type Number Type
2 QBL5/3500 (6076) 2 QBL5/3500 (6076) 3 DCG5/5000GB (872A)
3 QQE06/40 (5894) 6 QE06/50 (807) 8 DCG4/1000G (866A)
1 OA2

1 E80L (6227)

1 EF91 (6AM6)


ITU Country
ITU Country