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U /~/~ ' K< tc ~u2 Cx ctvif-tj!7 ; U c ca CL i/y zr, Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 nvwv u-'- c~ 1 cc yb~ ~G~e?(/t uC A New Ficid for the Experimenter Over-all view of the color television system. The bottom unit on the left is the flying spot scanner which was made from a discarded TV set. The color slide to be transmitted is fastened to the face of the cathode-ray tube and is visible just beneath the upper chassis. In the center of the picture is the photo- cell chassis with three photomultiplier tubes equipped with red, blue and green filters facing the scanner. On the right is the sync and blanking generator. This, too, was made from a salvaged TV receiver, and is also part of the author's black and white television system. The coaxial cables from the photocell chassis carry the red, blue and green channels to the color unit, the upper chassis on the left. This is the heart of the system and contains a matrix for converting the three color signals to standard black and white, "I" and "Q" signals, plus the 3.58-Mc. color carrier oscillator, the color modulators and the burstsignal generator. I7H amateur television on its way to be- coming a popular phase of ham radio, it should be done in color. Since color TV has been confined primarily to commercial broadcast use, a great deal of planning and gathering of informa- tion was necessary before undertaking such a project. Such questions as what type pickup source would be desirable, could good color quality be obtained, what types of color filters should be used, and could junk-box parts be made to work had to be answered. After studying all of the facts and drawing up some circuits that would be satisfactory for amateur purposes, it was decided that it would be practical to go ahead with the project. Fig. 1 shows a block diagram of the system that was finally decided on and constructed. Type of Pickup Cost was a prime factor, and since this was an experimental project I decided to use the "flying spot scanner" type of pickup to transmit color pictures put on glass plates about 3% X 4 inches. These slides have been made with water colors, drawing inks, colored cellophane and trans- parency film. Briefly, the flying spot scanner depends upon a light source that is capable of scanning the color slide at the proper rate. The light at any one instant will depend on the den- sity of the slide at that point.. If the slide is in color the light will also be filtered as it passes through the slide. Assume now that the beam of light is passing through a red portion of the color slide- This * Box 8(17, Ilakot, City, Nebrn.cka. September 1960 Arniteur Color Te1'evis9*0 a simply means that the red dye in the slide absorbs all the colors except red. Therefore, this is the only color that will pass through the slide at this instant. If a photocell is now placed is front of the slide with a filter in front of it an that only red light will be allowed to pass through, then a voltage that is proportional to the light passing through the slide at that point will be developed by the cell. Now, if we have a second cell with a filter that will pass only blue light in front of it, and a third cell with a green filter, we will be able to produce every color of the rainbow, in- cluding white, simply by proper mixing of the three basic colors. Those who feel that regular black and white TV is on the far fringe of Itarn experintentatiora, had better catch their breath. ITOKYQ has built a color television systern which transmits slide pictures and drawings with ex- cellent quality. So far as we know, this is the first antatear color TV to be put on, the air, at least in the United States. The signal is very sintilar to the NTSC standard for cottwnercial broadcasters and can be viewed on a standard color .set with a 4211-11c. con- carter. It is also contpa-ti.ble witit reg- ular black and white receivers. By using junk-box parts and sections of t ice-awav TV sets rite author o g tt >> kent thr cost of rite system to $175. Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 j +!~, Rc%BlaterandGr~e1G C~ US a,41 61ters For example, assume it is desired to produce yellow. Red and green when mixed in the proper proportion will produce this color. Therefore as the light beam is passing through a yellow portion of the slide, the red cell will see red information and the green cell will see green information. When these two separate signals are recombined, the original yellow will be reproduced. Let's take one more example. If we want to reproduce white light, which is actually a mixture of all colors, it will be found that the red photocell will see about 30 per cent of the light, the blue cell will see about 11 per cent, and the green cell will see about 59 per cent. When these three signals are -added together, the original white will be reproduced. The amount of light actually reaching the photocells after passing through the color slide and the selective filters is very small, so sensitive photomultiplier tubes were used. The green and blue channels use 931-As and the red channel uses a IP22. These photocells are presently on the surplus market for about 85 each. The filters that were used in front of the red, blue arid green photocells were Kodak Wratten filters Nos. 25, 478, and 58, respectively. Each of the photocells is followed by a three-stage video amplifier em- ploying GAK5s. This unit was built on it separate chassis along with its own electronically-regulated power supply. Light Source Readily-available used television' receivers at iVeit h-~ pricurneIvc re pro , em oT a scaurung iglrt source. In this instance, an old RCA IKCS 28 chassis was obtained for $5. All of its front-end tubes were removed, ]caving onll the sync, video amplifier and deflection circuits intact. Arno nee rectifier tube was ~icT reL l rri pun;ll7'l with the one that was already in the set, since it was desired to use this power supply to run the re- mainder of the color unit. Provisions were also made to feed in_ Wanking au s r ulse~ta.cnu- trol thLesca nrn For the light, it 5AXPI picture tube was used. This is it TV serviceman's 5-inch substitution type tube. When selecting a tube to be used for color television, it must always be kept in mind that the light transmitted by the tube must have sufficient amounts of the three basic colors. If this condition is not met it will be impossible to obtain a satisfactory signal on all colors. Red is the hardest color to reproduce from the stand- point of both the photocell and the light source since each is down in output at this frequency. Matrix The real problem is still to come. The red, blue and green signals must now be prepared in such a manner that all their information can be put on one carrier and also produce a signal which is compatible with standard black and white re- ceivers. This is the job of the matrix. Its first function is to produce a black arid white signal from the three color signals. This is simply a matter of mixing the color signals together in the right proportions. The black and white signal will also be used in color reception as a mixing signal. By properly adding and subtracting the. red, Close-up of the photocell pickup unit showing the end which normally faces the scanner. The red, blue and green photomultiplier tubes are mounted front and center with their respective color filters wrapped around them. The gain controls on the front panel are for balancing the three channels. Behind the photomultiplier tubes are the red, blue and green three-stage video preamplifiers, and at the rear of the chassis is an electronically-regulated power supply. The coaxial cables on the right carry the three color signals lo the matrix. QST, for Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 And here (don't laugh, now!) is the transmitter. The In- verted socket at the right holds a 12AT7 parallel line oscillator for 420 Me. Shown above the chassis are ilia plate and cathode lines and the heater r.f. chokes. On the left is a 6CL6 modulator. It and the 12AT7 are connected in series across the plate supply, and video drive is applied to the 6CL6 grid. WCKYQ admits the irony of such a simple rig for so complex a system, but points out that TV signals are wideband and that the little 5.wattor does fine for local work. A 420-Mc. converter and standard color (or black and white) set are used for reception blue, and green signals electronically, all the in- formation they contain can be condensed into two signals if the black and white signal is prop- erly mixed with these two signals at the receiver. The two new signals that take the place of the red, blue and green information are called "I" and "Q.'' Now we can make use of a very special typo of modulation called "quadrature modulation." This is a system whereby two signals can modu- late one carrier by making one signal always lag behind the other signal by 90 degrees. The color .modulators operate on the standard color fre- quency of approximately 3.58 islc. and are of the balanced-modulator type. Effectively, we put all the color information on a single carrier and then suppress the carrier so that we are sending all the color information by d.s.b. Next, we mix this color signal with our black and white signal and with the standard sync pulses. Sync and Blanking Another ea L TV receive we obtained to generate the, svne pulses This receiver Was- left intact an is ac iuFtcd to receive a local station. The s nnc cant then be taken from the sync circuit in the receiver without an additional et ui meat being re( utrec . y obtaining the sync in this manner a superior pulse can be had with the minimum of cost. The blanking generator is built as a subehassis on this same unit. It is a group of multivibrators and clippers which effectively produce a pulse that will turn out the light source during the retrace period of the electron beam. pfhic month September 1935 The editorial 25 years ago was a plea to amateura to cooperate in cutting down QllM by three simple meth- ode: using the proper bands to'avoid jamming DX with local rats-chewing, trimming power to just that necessary for the Q130 in progress, and ceasing to teat on radiating antennas, using dummy antennas instead. September 1960 The only thing left now is to produce a pulse which will initiate a reference signal for the color receiver to lock on so that the proper colors will be reproduced. This signal is called a burst signal and is sent only during the period of time when no picture information is being transmitted. By making good use of the junk box the com- plete project cost a total of about 5175. The results have been very satisfactory. Colors are true and brilliant. All colors have been faithfully reproduced, including some of the hardest, flesh tones. There is it great deal of fun to be had in explor- ing this now phase of amateur radio, and I am sure that we will begin to hear a considerable amount from now on about experiments in ama- teur color television. Unlimited ideas and meth- ods are waiting to be tried out, and many systems like mine can be built out of readily-available parts. There are many different ways of produc- ing color TV and this is only one of them. So let's go color - there's nothing quite like it in ama- teur radio. q T- Note: Practical circuit dinrrams have been left out of this article, intentionally. Anyone experimenting with rotor TV would havo to acquire enough knowledge of the subject to devise his own, based on current commercial practice and standards if regular receivers are to be used. For more in- formation, consult texts much as Intredttetion to Color TV, grid Edition by Kaufman and Thomas, published by Rider. - Editor. The magazine served a pot pourri of technical fare inchtding articles on Plato tnorbtlation of pentodes .. . an all-purpose s.s. mnperhet with turret-type automatic coil changing ... it new type u.1,.f, transmitter a frequency-Lock multi-vidor .. a fh xible e,c.-controlled transmitter ... Plus technical topics and three pages of hints for the experimenter. The seventh international DX contest was hailed no "the greatest in the history of amateur radio." The win- der was W351 who rolled up 40,503 points in cnntacting 50 countries on nil continents. "Booth-takincll" nail QST. . Y'ho third tumual Field Ilay won boiled as beat Yet - the United Radio Amateur Club of Wilmington, Calif. took top honors with 1116 points. 15 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 May 14, 1963 Filed Sept. 9. 1960 I6~ R. E. GRAHAM TELEWRITING APPARATUS 3,089,9+18 INVENTOR R. E. GRAHAM A7'TORN Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 May 14, 1963 Filed Sept. 9. 1960 FIG. 2 R. E. GRAHAM 3,089,918 TELEWRITING APPARATUS HORIZONTAL DEFLECTION a COS cut r TRACKING UNIT 'OUT OF CONTACT' V 'Y'. INVENTOR R. E. GRAHAM ATTORNEY Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020029-4 so ~sI ~s2