NAEB Newsletter (Aug 1958)

TV TECHNICAL TIPS —Cecil S. Bidlack In almost every television station operation, occasions have arisen when the intercommunication between the director and the camerman is not loud enough to overcome ambient noise. Donald K. Haahr, of the WOI-TV staff, sends along the methods used there to overcome this difficulty as developed by two of their engineers, Thomas F. West and Leo E. Runge. The two most obvious program offenders are sportscasts and musical productions. Quick camera changes during the climax are important, yet this is usually the time of most program volume. Our ill¬ ustrations show two of the three methods used at WOI-TV to assure its cameramen getting necessary instructions in spite of program or crowd noise. The first step in this improvement was to con¬ struct a bracket which mounts the microphone as¬ sembly of a Western Electric Type 52 AW headset to a war surplus double cushion headset (see photo). The WOI-TV crew likes them because they offer intercom to both ears, at the same time blocking un¬ wanted sound from the normally used ear. They are rugged and they are more comfortable, especially in cold weather. The second step was to incorporate an amplifier at the director’s position which fed a higher talk level to the intercom circuit. The talk voltage was raised from the usual .5 volt normal level to approximately 3.0 volts, which is about the maximum, above which cross talk may be observed in the video circuits of the camera cable. The addition of a key switch al¬ lows the director to have the line audio amplified on his headset alone. One disadvantage is that the di¬ rector’s mike is amplified into his own ear piece. As a result of this second step it became evident that it would be desirable to have an amplifer at each headset location with its own volume control; in this way the audio in the intercom circuit could be normal mike level. The third step was to build a transistor amplifier in a x 2 1 /4" x 4" aluminum minibox shown on the panning handle of the camera. The power supply is self-contained and to date the bat¬ teries have lasted over three months using them about three hours per week on remote pick-ups. The cost of materials is less than ten dollars per unit. If you’d like to complete constructional details of these amplifiers including a parts list, schematics and the layout of the plexiglass panel mounting the com¬ ponents (see photo), we’ll be glad to mail them to you upon request. ***** We are also in receipt of a brochure, from Mr. Haahr of WOI-TV, of a color television recording and reproducing system developed by Dr. William Hughes of the Iowa State College Experiment Sta¬ tion. The system uses 35mm black and white film. Electronically, the brochure states, the ICS system is not much more complicated than current black and white film chains. Mechanically, it is much simpler than even the simplest black and white film chain since it uses a continuous (non-intermittent) film movement. If you wish the brochure on this color television recording and reproducing system, write to the Director, Engineering Experiment Station, Iowa State College, Ames, Iowa. ***** There’s an excellent article in the June 1958 RCA Broadcast News by John H. Roe, titled “How to Get Good Picture Quality from the TK-15 Studio Vidicon Camera.” This paper discusses the use of the new 7038 vidicon and tabulates the important points to remember to obtain maximum picture quality. It also tabulates steps in camera set-up procedure. The importance of lighting is stressed as well as the necessity for correct adjustment of target voltage, beam current, illumination and lens openings to give maximum signal to noise ratio, low lag, depth of focus and normal output. The article has been reprinted and is available from RCA upon request. ***** The B.B.C. has developed a video tape recording system which they call Vision Electronic Recording Apparatus. The May 1958 technical issue of the AUGUST, 1958 Sheraton-Fontenelie 9