by Elliott P. Fagerberg, Consulting Author, Geneva, Switzerland-A report on the addition of a new dimension to telecasting in Europe. (BROADCAST ENGINEERING January 1965)

Helicopters are being used increasingly in several European countries for "live" telecasts of outdoor events. Basically, helicopters provide two important advantages:

They make possible airborne, overhead camera shots, and they provide a support for equipment used to' relay signals from remote cameras on the ground.

Success in using helicopter techniques has been reported by Radio Television Francaise (RTV) in broadcasting the "Tour de France" bicycle race. For these telecasts a helicopter is used both for direct aerial shot and as a relay for signals transmitted from video cameras mounted on motorcycles.

A transistorized image-orthicon camera is used for the airborne pickups. This camera is provided with a synthetic-resin cover for protection from the weather. Closeup pictures are obtained from cameras mounted on motorcycles that follow the racers; equipment aboard the helicopter is used to' relay signals transmitted from the motorcycles. The signals are picked up with two FM receivers tuned to' 492 and 532 me and are retransmitted from the helicopter by two FM transmitters, one operating on 650 me with an output of 5 watts and the other on 780 me with an output of 50 watts. The video signals from the helicopter camera are also transmitted through these units. A conventional radiotelephone system is used for relaying instructions from the helicopter to the motorcycles and a truck-mounted receiving station.

Circularly polarized, printed-circuit receiving antennas are used on the helicopter and the motorcycles. The helicopter antennas are extended and retracted by electric motors.

A similar system has been used by the Radio Televisione Italiana (RAI); a helicopter makes possible coordinated pickups from two cameras mounted an automobiles (Fig. l ) and a third all a motorcycle (Fig. 2). Although RAI anticipates putting a cameraman in the helicopter, the aircraft is now used only as a relay station.

On each of the station wagons is mounted a transistorized camera using a 3/1 image orthicon. A generator driven by the engine of the vehicle is used to charge batteries which in turn power the cameras.

The helicopter and auto transmitters have outputs of 6 watts each. The motorcycle transmitter power is 3 watts. Three receivers with different types of antennas operating in diversity are employed at the receiving truck (Fig. 3). A diagram of the system is shown in Fig. 4.

A system similar to those already described has been used by the Belgian Radio and Television System. During the race, the helicopter flies over the course at an altitude of 900' to WOO'. The video is sent from the motorcycles to the helicopter by .7-watt FM transmitters operating in the 500 me band. Aboard the helicopter is a 50-watt FM transmitter which retransmits the video signals in the 500 me band. Using an omnidirectional antenna (under the aircraft in the cover illustration), the helicopter relay permits constant contact with a fixed ground receiving station within a radius of about 15 miles. The ground station uses a directional antenna with a gain of about 12 db.

Microphonics due to mechanical vibrations of the helicopter proved to be a serious problem in initial tests of the equipment. This was eliminated by shock-mounting the electronic equipment in the helicopter.

Interference was another serious problem. It was produced by signals from other stations operating entirely outside the desired frequency band and by the radiotelephone system aboard the helicopter. The difficulty has been eliminated by inserting band-pass filters in the antenna transmission line.

To give the helicopter pilot maximum freedom in maneuvering his craft while following the races, helicoidal antennas have been installed on the motorcycles and the helicopter. The use of circularly polarized antennas on the motorcycles reduces the effects of interference due to reflected waves at some relative positions of the helicopter and the motorcycles. Belgian TV engineers are convinced that ground based stations for such telecasts should be located in rural areas to minimize the effects of industrial static.

One serious problem remains to be solved. The sync generator in the portable camera does not produce pulses that are satisfactory for good video transmission. It has been the practice to replace this information at the ground relay or the studio by pulses generated locally. The ground-based sync-pulse generator is synchronized with the signal from the helicopter by means of a "slaving" unit. This synchronization has not worked satisfactorily because of the numerous breaks in transmission from the motorcycles to the helicopter. A proposed solution is to use a return transmission channel to "enslave" the sweep of the portable camera to the sync generator at the studio.

The Israel Broadcasting Service has made satisfactory use of a "military-type" transceiver for live telecasts from a helicopter. While being unable for security reasons to disclose details of the cameras used, Israeli radio engineers report that a BBC-type lip microphone has been used effectively to exclude undesired noise.

Live telecasts have not yet been reported in Scandinavia, but in both Sweden and Norway helicopters have been successfully used for filming outside events for TV broadcast. The Swedish Broadcasting Corp. has obtained effective stabilization of the camera by means of a gyroscopic device. Engineers for the Norwegian Broadcasting Corp. have not yet been able to record a running commentary on the film of aerial shots because of noise within the helicopter.

A number of European broadcasting organizations report successful use of helicopters for making antenna - pattern measurements. These organizations include the "Deutsch Welle" of Cologne and the Bayerischer Rundfunk of Munich in Germany, the Oesterreicher Rundfunk in Austria, and the Independent Television Authority in Great Britain.

The latter organization has used helicopters for testing new television transmitting antennas. In verifying the effective radiated power directed toward France from Dover, the Authority's engineers were able to determine very accurately the radiation pattern of the antenna mounted on the transmitting mast. Also, power-loss measurements over a very long radio transmission path were carried out with the trans­mitting equipment supported in space by a helicopter.

Thus it can be seen that, although the methods of usage vary from country to country, the helicopter is assuming an increasingly important role in European television broadcasting. .•.

           Fig. 1. Auto-top camera used in Italy.  Fig. 2. Motorcycle camera uses vidicon.   Fig. 3. Multiple-antenna ground station.