. The Bell System technical journal . -up time. This require-ment is met with plug-in terminating impedances, pads, leads, etc., andwith oscillators and detectors tuning continuously over a wide range offrequencies. Several filters of the same type are normally testedsimultaneously, all being measured at one frequency before the nextfrequency is set up. Contact fixtures for particular types are providedwhen justified by quantity requirements, in order to facilitate thetransfer of test leads from one filter to the next. Transmission loss characteristics of channel filters under variouscondition
. The Bell System technical journal . -up time. This require-ment is met with plug-in terminating impedances, pads, leads, etc., andwith oscillators and detectors tuning continuously over a wide range offrequencies. Several filters of the same type are normally testedsimultaneously, all being measured at one frequency before the nextfrequency is set up. Contact fixtures for particular types are providedwhen justified by quantity requirements, in order to facilitate thetransfer of test leads from one filter to the next. Transmission loss characteristics of channel filters under variousconditions are shown in Fig. 14. The solid curve illustrates a normalfilter. The loss in the passband is approximately db, with distor- MANUFACTURE OF QUARTZ CRYSTAL FILTERS 531 tion of about db over a band 3 KC wide. The peak losses arefrom 75 to 90 db, with the intervening valleys approximately 65 other curves illustrate three types of defects occasionally ob-served, namely: {a) displacement of one attenuation peak caused by. TWINNING INQUARTZ PLATE FREQUENCY Fig. 14—Insertion loss characteristics of crystal channel filters, showing the effectsof deviations from normal conditions. twinning in one of the crystal plates, (&) abnormal distortion caused bya per cent error in resonance adjustment, and (c) low loss at peakscaused by leakage across a crystal or by components which are in-adequately balanced to ground. As an aid to locating the particularcomponents or adjustments which are responsible for such defects, acatalogue of trouble-shooting instructions, arranged by classes offilters and types of symptoms, has been compiled. Cleaning, finishing and labelling constitute the remaining operationson crystal filters. High temperature processes such as vapor degreas-ing and baking of the finish are inapplicable here because of the natureof the component apparatus in the filter. The surface is scratch-brushed, washed with a solvent and sprayed with aluminum
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
