Since the 1964 FCC requirement that all television sets provide UHF reception, manufacturers have spent considerable time and money on the design and development of economical U1IF tuners.
Size, performance, cost and reliability are the objectives in tuner design. The introduction of small screen portable sets has made the dimensions of the tuner a decisive factor in design. A miniature UHF tuner is attractive in that it may be used in all sets, but miniature units are not efficient in performance and are expensive to manufacture. A larger tuner, tor example, 2,7" x 1.3" x 2.8n* is more efficient easy to manufacture, but often will not fit in small sets. The size problem is solved by manufacturing different size tuners, but this requires additional manufacturing lines and increases inventory cost,
I ransistorized UHF TV tuners are superior to tube types because they can be manufactured in small sizes, are more officii nt and stable, and do not require periodic maintenance while providing a longer life span Figs, la, b and c show three sizes of UHF tuners presently in use. The first two can be used in small screen portable sets while the larger is suitable for console sets,
! he UHF TV tuner described here was built to demonstrate the capability of the new UHF oscillator device, SE3005, and to provide guide lines for its use in tuner design. After the basic size of the tuner is established the design problem would be to assure optimum performance, simple construction, reliability, low cost and ease of manufacturing. Fig. 2 shows the finished tuner. The two compartments on the left are double tuned passive rf pre-selector cavities, while the third, on the right, is the local oscillator cavity. The center section also houses the mixer diode and associated components.
The pre-selector rf cavities have capaci-lively tuned lines. The lines and the cavities are self resonant at i ,000 MHz. The lines are selected by an empirical method, rnathe-matical analysis is difficult because the frequency of operation spans from the point where simple transmission line theory can
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