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standard carricr frcHjucncics and tlić poorest figurę ohtaincd becomes the "raied performance" of the tuner.

Spurious Response

The thiiil type of measurement which indicates the capahility of a tuner in rcjecting interference is the spurious response test. Here the tuner is set to each of the standard carricr frequcncies and a signal generator with suflicient outpui voltagc tuneri over a wide frequency rangę. At each frequency where the tuner shows an audio output the signal generator out-put voltage is ad.iustcd so that the measurement procedurę of the usable sensitivity test is followed. This volt-age wilh the usable sensitivity test in-put \Oltagc is comcrted to a ratio and then expressed in decibels. The number of decibels givcs the amount of spurious response rejection by the tuner. A number of these spurious response fre-cjucneies may łie found, possihly due to forms of r.f. distortion within the tuner. Two particular ones will have to be recorded separately: image response and i.f. response. These frequcncies may turn out to be 10.7 mc. for i.f. response and equal to the tuned fre-quency plus 21.4 mc. for the image response frequencv of the tuner.

Other Tests

The other tests normally jterformed on tuners arc self-e.\planatory and it is merely a case of following the con-ditions specified in the standard. Some of these tests werc madę in the past

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