Mac's Radio Service Shop: Television DX |
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AT&T "Reach out and touch someone" commercial, c1979 Before there was the World Wide Web (aka the Internet) and unlimited cellphone calling plans, personal communications over any distance for most people was limited to local telephone calling areas. Long distance calling rates were high enough to prevent casual calling of family, friends, and businesses in the U.S. Overseas call rates were extremely prohibitive. The price to "Reach out and touch someone" could set you back 10¢/minute or more. Even today, an old-fashioned landline plan from AT&T can cost you $3.50/minute to the UK, $4.50/minute to Japan, and $5.00/minute to China. Depending on where you lived, calling someone in the next neighborhood over could be a long distance call, while calling 50 miles in the other direction would be considered local. Toll-free "800" long distance numbers were implemented to encourage people to make contact with businesses without incurring additional charges. Late night TV shows were famous for using 800 numbers to entice customers into buying Ronco gadgets and term life insurance policies. Radio was the primary medium for receiving communications from far away at no cost other than equipment procurement. CB radio enabled two-way communications up to fifty miles or so without the need for a special license, and of course a Ham licensee could span the globe. If you were satisfied with merely listening, shortwave radios facilitated the "magic" of hearing broadcasts from around the world. Under favorable atmospheric conditions, particularly at night, even a cheap AM/FM radio could pick up stations half a continent away. What was considered annoying interference to most listeners was big game for "DX" hunters. "DX" is Ham shorthand for "long distance." This 1951 installment of "Mac's Radio Shop" describes what became a real thrill for TV owners: TV DX. The most enthusiastic tuners-in went to extremes to pick up TX stations many states away, even if the picture and/or sound quality was barely perceivable.™ See also TV DX - July 1958 Radio−Electronics, Mac's Radio Service Shop: Television DX - September 1951 Radio & Television News, Tips from a TVDX−er's Notebook - November 1957 Radio−Electronics. Mac's Radio Service Shop: Television DX
Suddenly Barney, the "hired hand" of Mac's Radio Service Shop, slammed his solder gun down on the bench and demanded of his boss: "Mac, what's so doggone funny? You've been grinning like a television toothpaste commercial ever since you came back from lunch." "Well," Mac explained, "by the time I got over to the Dutchman's this noon, all of the counter stools were taken, and I had to sit in a booth. While I was eating I couldn't help but overhear a hot antenna argument going on between a couple of rabid TV fans in the booth behind me. Each guy was whooping it up for his antenna system and using as evidence the distant television stations he pulled in during that 'opening' we had around last Decoration Day. Number One gave all the credit to his battery of Yagis, while Number Two was convinced that his collinear array was what enabled him to yank in the DX." "And that's side-splittingly funny?" Barney questioned with arched eyebrows. "In a way it is. I kept thinking how amusing it would be if I butted in and related my own experience during that period. You will remember that I had just received my new television chassis at the time and was waiting on a cabinet. However, I was so eager to try out the high-fidelity amplifier on a couple of speakers I had at home that I unpacked the chassis and set it on top of the shipping carton, cut a twin-lead folded dipole roughly for the FM band and tossed it on a desk beside the set, slid in a picture tube, and turned on the set. "While I was adjusting the ion trap on the seventeen inch tube I was using, I began to notice pictures on the screen. In the next couple of days, using that very poor antenna, a yardstick for an antenna tower, without any booster of any sort, and at this Northern Indiana location seventy miles from the nearest TV transmitter, I logged Cuban stations on Channels 4 and 6; Miami and Jacksonville, Florida, stations on 4; Chicago stations on 4, 5, 7, and 9; San Antonio, Texas, on 4 and Houston on 2; Milwaukee on 3; Louisville, Kentucky, on 5; and Indianapolis on 6. While there was fading on some of the signals, both sound and picture were received in each case with sufficient clarity to make identification easy and positive. In many cases, the reception was perfect, without the slightest snow or noise." "You don't suppose you could have stumbled on some kind of a super antenna in that twin-lead job, do you?" Barney suggested hopefully. "Not a chance," Mac replied with a chuckle. "Just to make sure, while Cuba was rolling in on Channel 4, I took off the antenna and touched one of the terminals with a screwdriver. 'Television Para Todo' came in almost as well as it had with the antenna. "No," he continued, "the point of the whole thing is that the antenna efficiency seems to mean little during these periods of freak reception. In fact, a low antenna may actually do a better job of picking up DX at such a time than will an antenna mounted on top of a high tower. Either refraction or reflection causes the distant signals to come in at pretty steep angles. The fact I could pick them up down in the bottom of this river valley proves that. Signals from fairly close stations, on the other hand, are usually not subject to so much distortion and continue to be picked up better by more elevated antennas. As a result, an antenna that is really up in the air picks up enough signal from a nearby station to interfere seriously with a DX signal. A low antenna, on the other hand, gets the distant signal just as strongly and without the interference from the close station." "Then you think that when one of these freak DX periods start, the thing to do is to start looking for faraway stations with a tuning knob in one hand and a folded dipole in the other." "It's worth a try, anyway," Mac said, smiling at the graphic picture Barney's words evoked. "One thing in favor of such a system is that it allows you to switch the antenna around much quicker than can be done with a rotating motor, and that is a distinct advantage in this freak reception. The signals from Texas were received best with the ends of my folded dipole pointing southwest and northeast - exactly opposite to what a person would normally expect and indicating that the signal was arriving by way of a most devious route. Furthermore, I counted as many as five separate ghost images on the signal from Houston, some displaced from the main signal by as far as three inches on the sixteen-inch screen. These ghosts kept moving back and forth behind the main signal, and by turning the antenna, the chief signal and one of the ghosts could sometimes be made to exchange roles. Often the signal arrived in the form of closely-spaced waves of strength, and being able to whirl the antenna about quickly during the peak of the wave permitted the best position to be readily determined. "Next time, though, I intend to use a special antenna I am making up just for freak DXing," Mac continued. "It consists of a folded dipole with end sections that telescope like the slide on a slide-trombone. A telescoping reflector is also used, and both units are mounted so that the space between them can be easily varied without up-setting their relative alignment. The element sections and the 'boom' are marked so that the array can be quickly set up for any channel." "Why go to all that trouble when you say the efficiency of the antenna is unimportant when the DX signals are really piling in?" "I'm not trying to increase the efficiency of the antenna," Mac explained. "What I want is an antenna that is more one-directional to help in establishing more accurately from just which direction the signal arrives; furthermore, by being able to tilt the simple array, I hope to get a rough idea of the angles at which the signals come in. Still another hoped-for advantage lies in the possibility of doing a better job of separating several stations likely to be found occupying a single channel during one of these unusual periods. You should have heard five different stations battling it out on Channel 4 like cats fighting over a fishhead as I did last May 30th. That certainly makes you want something to help unscramble them." "What produces DX like that, anyway?" Barney asked. "I don't know," Mac readily admitted. "As a ham, you are, of course, familiar with the theory that clouds of ionization frequently appear about fifty miles above the earth and reflect back to earth high frequency signals that ordinarily would never be returned. This 'Sporadic-E Ionization' as it is called may happen any time, but it occurs most frequently during May, June, and July. That could explain my experience except for one thing: that the signals from Texas seemed to be arriving from either the southeast or northwest-exactly opposed to the southwest direction in which Texas lies from here. "Some of my friends," he went on slowly, "who know a lot more about such things than I do, tell me that there is a growing theory that under certain favorable circumstances a current of air under exactly the right conditions of moisture, barometric pressure, and temperature can actually act as a huge waveguide and 'pipe' a high frequency signal from one part of the earth to another. Maybe that is the answer. At least it would permit the signal path to have a bend in it, as that one from Houston seemed to have. "At any rate," he continued, "I'm going to do all the 'observing' I can every time one of these openings occurs. Hams have been doing that for years, but their numbers are very small compared to the millions looking at TV screens every day. If only a small percentage of these TV fans become interested in noting some of the factors that affect abnormal DX signals, perhaps we can learn enough about them to enable us to control these conditions." "Could be," Barney agreed with a shrug. "Today's miracle is tomorrow's normal occurrence. I keep remembering that at one time they gave the whole spectrum above two hundred meters to the hams because they thought these frequencies would never be of any practical value - the Indian givers! Next time the TV channels get hot, just let Old Barney know, and he will be right in there waving a folded dipole alongside you!" Mac's Radio Service Shop Episodes on RF Cafe This series of instructive technodrama™ stories was the brainchild of none other than John T. Frye, creator of the Carl and Jerry series that ran in Popular Electronics for many years. "Mac's Radio Service Shop" began life in April 1948 in Radio News magazine (which later became Radio & Television News, then Electronics World), and changed its name to simply "Mac's Service Shop" until the final episode was published in a 1977 Popular Electronics magazine. "Mac" is electronics repair shop owner Mac McGregor, and Barney Jameson his his eager, if not somewhat naive, technician assistant. "Lessons" are taught in story format with dialogs between Mac and Barney.
Posted October 2, 2020 |
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