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About RF Cafe
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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Hobbyists in the technical realm have in many ways contributed mightily to the advancement of professional scientific knowledge and practice. This is partly because many hobbyists are also career technologists, but the majority are tinkerers, experimenters and otherwise participants who come from all walks of life geographically, economically, professionally, and socially. Just as with university and corporate laboratories, some of the discoveries are the result of structured, preconceived plans of action and designs of experiments with certain goals in mind; many, however, are due to serendipitous events that are recognized by their participants as being significant. Such is the case of 'TV DX' as related in this story. TV DX is the use of unique opportunities in the atmosphere's ionization state to facilitate signal transmission and reception at distance much greater than normally experienced. Data collected by amateurs were, during the era of over-the-air VHF and VHF television broadcasting, included in studies and theories created by professional scientists and engineers to help better understand and predict communications phenomena - both for exploitation and for interference avoidance. The same is true today for other venues like solar activity observers and pollution status reporters.
<--- Very interesting
story of unintentional radio DXing (starts ~ 1/2-way in)
Jean Shepherd: Code School - April 13, 1965
With the sunspot count on its waning side, overall effects of the now-famous 11-year cycle are being studied, with particular interest in vhf propagation.
In past years, reports which told of extraordinary long-range reception were often regarded as cases of mistaken identity or perhaps even a deliberate hoax. However, during the past 12 months, we have developed a sixth sense which makes us look twice at such dx loggings. After all, dxing the TV frequencies has been largely a case of exploring the unknown and uncovering new items of information, bit by bit, until we have an end result which indicates a new form of dxing and another mode by which the alert TV dx fan can drag in those faraway television stations.
March, 1958, was a slow month dx-wise for the greatest majority of TV dx fans across the country. One very unusual occurrence was a full-scale Sporadic E skip break, on March 15, which brought a 6-hour Es session to just about every section of the country west of the Mississippi. Signals were strong with much co-channel interference as high as channel 6. At the height of the opening, Ron Pugh of Ft. Bragg, Calif., switched to channel 7 to find KLZ-TV, Denver, Colo., showing with fast-fading audio and video. Reception was short lived, however, running from 1820-1832 PST. The distance involved is nearly 950 miles and the event represents one more instance of high-band signal propagation over a Sporadic-E skip distance during a widespread Es opening on the lower channels.
Another totally unexplained series of loggings is reported by Ray F. Boyd, Zirconia, N. C., when on the night of March 14 he logged seven California stations, including KCOP, channel 13, and KABC-TV, channel 7, both Los Angeles. These reports, if accurate, involve distances of nearly 2,500 miles on the high-band channels and come very close to providing a set of distances that may not be approached in the near future by TV dx enthusiasts.
FM and TV DX
Although you may not be completely aware of it, your television dx reports serve a very valuable scientific purpose. After Radio-Electronics finishes with the compilation, the reports are filed away for later study by prominent groups of scientists. Such reports are of definite scientific interest, as they illustrate freaks of nature and are therefore subject to further explanation by properly qualified authorities.
However, these reports do not serve as an end, but merely as a means toward an end. To understand completely the actions of vhf-uhf signals in our atmosphere, stratosphere and ionosphere, we should study not only the piece-meal samples of the spectrum (such as TV provides). We must also make use of every faculty available to us, including every type of unusual dx report which falls within the vhf-uhf region.
This is where the Frequency Modulation (FM) band enters the picture. FM helps fill a frequency range which lays between channels 6 and 7. Many other services such as taxi, police, airport and amateur have room within this range, but only FM is commercially available to the public. We have good reason to believe that the FM band's dx actions will resemble to some extent those of television channel 6, but we cannot be sure. To help fill in our knowledge holes, we are instituting an FM dx section, to be run at the beginning as a sidecar of the Television Dx Column.
Some major differences between the two, however, will be immediately self-evident. As FM dxing is not an organized hobby on a national scale, we will find it necessary to set our own limits as to what constitutes dx via FM and expand these guide posts as the hobby develops. We also wish to carry an occasional paragraph on antennas, tuner - and the like, purely from a sensitivity standpoint. It is hoped that both the hobby and column will grow together. To get the ball rolling, FM dx reports, lists of stations received, and so on are needed to begin our book of standards. Send along your results for listing.
The first and last weeks of July normally produce a good deal of Sporadic-E reception, with many sessions running as high as the lower FM channels. The best hours of the day continue to be 0700-1000, 1200-1400 and 1700-2000, all local standard time. By August, E sessions will begin to dwindle toward the normal fall low point, with any sessions after Aug. 15 running from 1600-2100 local standard time. E skip may hold up weakly as late as early September in southern latitudes along the Gulf Coast. One period expected to be especially hot for Es is July 25-28.
The summer months, with their slow-moving frontal systems and evening temperature inversions, is always ideal for extending the normal ground-wave range. Just after sunup and from sundown until midnight are periods usually especially productive over coastal, Gulf Coast and Great Lakes paths. Early evening and on until early morning hours will bring the best high-band ground-wave reception across the Great Plain States. Again, keep tabs on your fringe-area stations and watch for signs of general improvement in fringe-area signals.
The one major meteor shower of the year is due to become apparent in the early morning hours of Aug. 5-15. The Perseids shower is an annual occurrence, bringing joy to the heart of meteor-burst enthusiasts all over the country. Bursts on the high-band TV channels (7-13) are especially profitable during this period, peaking from the 12th-14th. Careful planning and the checking of operating schedules of station 800-1,400 miles distant on channels 1-13 may result in some excellent loggings on your part, which you are not likely to intercept by any other form of wave propagation.
Reporters to the TV Dx Column are urged to drop a postcard to the TV Dx Column, Radio-Electronics Magazine, 154 W. 14 St., New York 11, N.Y. In return we mail you a set of prepared dxing forms. These are engineered to extract all necessary information from you the dxer and make dx reporting as painless as possible. Oh yes, they also function on the FM band ... send for yours today ... they're free!
Posted May 9, 2014