At the Radio Operator's Desk
At the extreme left is the short-wave transmitter with the short-wave receiver alongside. At the extreme right is the long-wave transmitter and the long-vave receiver.

Successful two-way radio communication with Chatham, Mass., was maintained by the latest Zeppelin, LZ129 on its second trial flight. This meant bridging a distance of 4375 miles by radio. Readers will no doubt be interested in the type of equipment employed on this latest airship. There are two transmitters, one for long waves and one for short waves, and two all-wave receivers. The aids to navigation consist of three sets of direction-finding apparatus.

The Transmitters

The long-wave transmitter can be tuned to any wavelength between 575 and 2,700 meters if 525 to 11 kc. Plate circuit modulation is employed. The power in the antenna is 200 watts for c.w. and 125 watts for telephony. The radiator consists of a two-wire antenna, 120 meters in length which can be unreeled by motor-winch. The receiver and transmitter employ the same antenna, equipped with an automatic device which switches it over when one speaks into the microphone. As soon as the speech stops for more than half a second, the installation automatically returns to receiving conditions.

The short-wave transmitter has the same power as the long-wave transmitter and can tune from 17 to 70 meters (17,700 to 4,280 kc). This range is divided into two overlapping bands. The antenna consists of a quarter-wave trailing wire, which is reeled out to the required length for the frequency in use.

The necessary power is supplied by an internal combustion motor and a generator which furnishes the electrical power for lighting of the ship. the power for the radio equipment and the heating current for the electric kitchen. The filament and plate supplies are obtained by means of the usual transformers. The necessary filters are placed in the lines in order to eliminate interference.

Two all-wave receivers are employed for reception, one to be used in conjunction with each transmitter. They are four-tube receivers employing two tuned r.f. circuits with a frequency range from 15 to 20,000 kc. subdivided into 10 bands. Switching from one band to another can be done quickly because all coils are mounted on the edge of a disk which can be rotated by hand.

The power supply for the receivers consists of a storage battery for both A and B supply, These batteries can be charged during the flight.

Radio Compass

Three different direction-finding receivers are employed on board the airship. The first one serves for the navigation during the flight, to find the location of the ship by means of cross bearings and to follow a course indicated by beam transmitters. It has a wave-length range from 300 to 1,800 meters. Two other directional receivers are employed for landing in bad weather.

A large loop is connected to two of these receivers by means of a transformer. A small loop is coupled to the third directional receiver.

The output of the three receivers is connected to two indication instruments. Each instrument has three pointers and each pointer is controlled by one of the three receivers. When the airship lands the ground crew of the airport operates three radio transmitters which give complete directions for grounding the ship, releasing the grab-lines, etc.

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