On-camera WRP20 System of IRTE Company (Italy)

By Oleg Jurtaev

Review contents:

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About five years ago on Italian and then on world market there appeared on-camera WPR20 system. The main task that was standing in front of the developers was to create universal on-camera system for video signal transfer. Really, they got the multifunctional set that includes few parts.

Among basic peculiarities of WPR20 the following should be mentioned:

• reliable construct6ion, corresponding to CCIR recommendations;
• waterproof transmitting radio frequency head;
• straps of transmitters fastening to any cameras;
• simple setting and use;
• high level of noise protection (special reflection protection system);
• low consumed power;
• build-in test opportunities for control over system? s condition.

WPR20 system consists of three parts: transmitting, receiving and control module.

Transmitting part Rcam-ctx represents a on-camera block with transmitting antenna. On-camera transmitter is specially developed for providing reliable radio connection with receiving block with leaving an opportunity of operation in all frequency diapason. In the scheme of transmitter already are integrated all necessary automatic functions what significantly simplified the operating process with equipment. Simplified construction of transmitter? s and antenna? s body provides solidity, necessary for intensive work, and also waterproof, what allows to use on-camera block out of studio almost in any weather.

Starting choice of video signal transfer channel, channel of service connection and level of video signal are done by pressing of only one button of power supply turning on. In few seconds after system? s activation there happens a shutting down of that button to avoid accidental pressing and following unplanned change of conditions of work settings.

High stability of frequency is achieved by use of phase lock loop controlled by microprocessor. Microprocessor controls also the level of video signal modulation constantly controlling the quality of transmitting signal.

Transmitting module of Rcam-ctx itself (left) and mounted to the camera

For reflection of operating parameters of system in on-camera block there is LCD display. On it current statistic information and warning signals (in case of defects appearance) are represented.

Technical parameters of transmitter are:

• frequency diapason is 2.4…2.7 GHz;
• amount of chosen radio channels is 16;
• entry power is 200 mW;
• amount of channels of service connection is 16;
• frequency diapason 9of service connection transfer is 912.75…915.3 MHz;
• RS-170 video interface;
• CCIR Racc.405-1 video signal emphasis;
• irregularity of AFC of video signal in the band of 10 Hz…5 MHz — +0,5 dB;
• group video signal delay is 20 ns;
• weighted signal/noise ratio is usually 65 dB;
• power voltage is10.5…16 V;
• consumed current is 600 A max.

Receiving part of on-camera WPR20 system consists of two units. First is receiving Rcv-79 head with antennas and second is control block Rcv/2500. Among themselves these two units are connected by triax cable. Receiving part is situated in the zone of optical visibility and transmitting on-camera block, and antenna directs into operator? s side. Control block can be situated on significant distance from receiving antenna (up to 350 m) and usually is situated in video projection booth, in equipment stand.

Rcv-70 wireless system receiving module

Control block allows to control the following parameters of transmitting part:

• Tally signal;
• diaphragm;
• parameters if receiving and transmitting antennas;
• parameters of 900 MHz filter;
• parameters of 2 GHz filter.

Control signals are sent by triax cable to receiving head, which has in its set transmitting EK-Rcv/2500 module, which transfers all control signals to on-camera block via radio channel.

As receiving transmitting block on receiving side is controlled by own microprocessor; that is why some control functions, such as tracking control of transmitting antenna are operated automatically. Automation of receiving/transmitting system allow achieving minimal level of emanation with storage of necessary quality of video transfer. Besides, automatic tracking system of transmitting antenna significantly lowers the level of impact of radio signal emphasis usual for TV studios. Due to automatic, receiving system operates independent from operator? s position.

Receiving block has an opportunity of setting of automatic equalizer parameters for setting of frequency and AFC form, which is changed if strong emphasis is present.

Detailed radio frequency channel among receiving and transmitting blocks provides additional opportunities for organization of service connection between operator and video engineer. As additional conveniences on receiving block there are two video outlets: one is video from the camera and another is programmed video.

Technical parameters of receiving part:

• frequency diapason is 2.4…2.7 GHz;
• number of chosen radio channels is 16;
• number of channels of service connection is 16;
• RS-170 video interface;
• Racc. CCIP 405-1 correction of emphasis of video signal;
• band of service connection channel is 300…3000 Hz;
• maximum length of triax cable is 350 m;
• power voltage is 220 V ±15%;
• operating temperature diapason is -10…+45°C.

One of the most interesting peculiarities of on-camera WPR20 system is the system of auto tracking of transmitting antenna, which is used for lowering of wave emphasis impact..

The of auto tracking system operation is special construction of transmitting antenna. Transmitting antenna consists of four emanating elements oriented in relation to each other on 90° and having circular emanating polarization. Emanating elements are connected to electron commutator, which provide necessary distribution of radio frequency signal. During processing of way of row of shot unfolding the auto tracking system tests each one of transmitting elements and chooses the necessary condition of system? s operation: emanates one elements (amplification is 8 dB) or all system. Such an approach allows controlling the quality of radio channel after each shot and chooses optimal parameters of transmitting system, what leads to effective lowering of energy consumption. In case of absence of answering signal from the base station antennas system operates as antenna with circular direction diagram.

Rcv/2500 control module

Absence of mechanical parts in the set of a system significantly increases its reliability and security, what is very important during assembly on video camera.

To justify totally its assignment as of reporters set of wireless transfer WPR20 components are situated in special firm case, which protects blocks against damages during transportation. Time for fixing and setting of system out of transportation condition is not higher than 10…15 min.

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