Television digest with electronics reports (Jan-Dec 1953)

10 NEW DEVELOPMENT in picture tube design, demonstrated at IRE convention, may simplify manufacture and servicing of TV sets and at same time cut costs and even improve picture. At least that’s what’s claimed by GE for its internal magnetic focus (IMF) tube, and judging from interest displayed by other picture tube manufacturers, device could find ready acceptance by industry very soon. IMF tube incorporates focusing device and ion trap within electron gun of tube itself. They’re set at factory, sealed in for perfect adjustment and focus for life of tube, according to GE engineers. This eliminates troublesome and touchy ion trap adjustments, simplifies production by cutting out cumbersome brackets and gadgets around neck of tube. Being permanently focused, tube requires no focus knob on set. GE claims it’s much easier to produce and gives better focus that the zerovoltage “self-focusing” electrostatic-focus tubes which were introduced as material-saving measure. GE says new tube will cost $1.50 more than present magnetically focused tubes, 25<? more than electrostatic, eliminates parts costing about $2.50. It may be used as High-powered uhf stations hitting fcc’s iooo-kw ceiling are still at least a year away, but manufacturers of the war-developed klystron tubes reported encouraging progress toward goal when we talked with them at this week’s IRE convention in New York. Varian Associates, which makes 12-kw klystrons for GE, reports it’s working on “early stages” of development of klystron to power 60-kw uhf transmitter, which, coupled with highgain antenna, could deliver 1000 kw ERP. Varian engineer N. P. Hiestand, in paper presented at convention, said new tube — being developed for GE — will probably be tested in 1954. Tube has 4 cavities, and 6 models will cover entire uhf band. Said Hiestand: “Thei-e’s no theoretical limit to the power which can be generated by klystrons.” Eitel-McCullough (Eimac) says progress is beingmade toward its 50-kw klystron (Vol. 8:10), and reports it will offer 12 or 15-kw klystron in about 3-4 months. DuMont, whose uhf transmitter is built around Eimac’s 5-kw klystron, is expected to bring out transmitter using diiect replacement for magnetic or electrostatic tube. Some sets may accommodate tube with no extra parts, but most will require close-fitting steel shunt band around tube neck and small centering device. GE will sample gun to other tube manufacturers, tube to set manufacturers in couple weeks, hopes to have new tube ready for fall market in several sizes. We observed pictures on set using IMF tube, found them clear and sharp, focus remaining satisfactory as line voltage was varied from 90-130 volts. GE says more than 100 of the tubes have been life-tested for 7000 hours under extreme conditions, equivalent of 4 years’ use. Tube uses 3 tiny alnico 5 magnets in focus assembly, one in ion trap unit. GE and almost all other tube manufacturers at IRE convention prominently featured the new 24-in. rectangular tubes in their displays (Vol. 9:11). Most of them are quoting delivery dates from May to July, although some small tube makers said model is now in production in non-aluminized version. Westinghouse showed new metalconed 24-&-27-in. tubes, both due for production in fall, in addition to glass 24-in. Eimac 12-kw tube. Eimac engineers are enthusiastic about new tube’s 45% efficiency, as compared to 25-30% in previous klystrons. They say this will mean big saving to telecasters in electricity. New 12-15-kw tube won’t be much bigger than 5-kw tubes (about 40 lbs.), will have externally tuned cavities. Three will cover uhf band. Though DuMont hasn’t turned out many uhf transmitters, Eimac officials say klystron isn’t the hold-up, adding that they’ve ali'eady made more than 100 of the 5-kw uhf tubes. DuMont this week announced new uhf transmitting antenna, to be made to its specifications by Gabriel Co.’s Workshop Associates Div. It’s a 2-bay 24 wavelengthsection slotted antenna, which can be electrically and mechanically tilted and incorpoi'ates null fill-in features. It has power gain of 21.5 at beam peak, 17.5 on horizon. Gates Radio Co. displayed TV transmitter at IRE convention and officials said company would have 500-watt vhf transmitter and 5-kw amplifier for delivery in 6 months. Company also plans uhf transmitter, but it’s still “in development” and won’t be available until 1954. ENTHUSIASM over performance of uhf receivers, converters and antennas is reflected in findings of 4-man engineering team from Howard W. Sams & Co., Indianapolis technical publishers, which spent 2 weeks in South Bend area testing uhf equipment. Crew used mobile equipment, made tests in more than 100 different locations at varying distances from station WSBT-TV (Ch. 34), using “virtually all uhf antennas currently available, all popularly used transmission lines and wide variety of uhf receivers and converters.” Among their findings: “Excellent results were obtained at distances up to 30 mi. from the transmitter [and] satisfactory reception could be obtained at distances up to 45 mi. through proper selection of antenna and lead-in combination.” As we did on our own visit to South Bend last month (Vol. 9:9), Sams’ field crew found area’s flat terrain apparently had no “dead spots.” In antenna tests, team found that height isn’t necessarily all-important factor. “In uhf fringe areas,” they concluded, “the first consideration is to select an antenna having sufficient gain rather than picking one with only medium gain and attempting to mount it at a higher elevation.” It’s far better, they added, “to install a highgain antenna at a moderate height than it is to install a medium gain antenna at an abnormally high elevation.” In latter case, losses in longer lead-in may counteract any gain achieved by greater height. Crew’s report pi-aised operation of uhf receivers and converters. “Tuning was not difficult and drift presented no serious problem,” they said, “and in most cases the converters would not require retuning from day to day, which speaks pretty well for their stability.” Complete report of field suiwey, including recommendations of antennas and lead-in lines for use under various circumstances, will appear in March-April issue of Howard W. Sams’ PF Index & Technical Digest. Compatibility tests and evaluation of network color transmissions are object of STA received by Philco’s WPTZ last week to transmit color 12:45-1 p.m. daily until April 30. STA specifies that tests aie “in order to obtain reaction of non-technical observers among the viewing public to the quality of black-&-white pictures during color transmission and to evaluate the quality of color transmissions when received via coaxial intercity transmission facilities.” “The Story of KPTV” titles atti-active 68-p. booklet put out by Empire Coil Co., owner of Portland’s KPTV, telling in photos and press clippings the story of construction and initial operations of woidd’s first commercial uhf station. It’s full of good material for other uhf enterprisers; write Empixe Coil Co., New Rochelle, N. Y., for gratis copy.