Reception band width adjusting method in am tuner

Abstract

Abstract PURPOSE:To attain simply and accurately the adjustment of a reception band width by measuring a high or low frequency of a reception frequency and substituting the measured value to a specific logical formula to set an object frequency for the adjustment. CONSTITUTION:A buffer amplifier 6 and a frequency counter 7 are provided to measure the frequency of a local oscillator 5. Then frequencies FL' and FH' of the local oscillator 5 while the inductance of a front end coil 1 is set to an Lmax and an Lmin is measured with an adjusting coil 3 and an adjusting trimmer 4 set to the initial state. Furthermore, an object frequency FH'' at the adjustment of the trimmer 4 is obtained according to the theoretical formula by using the values FL' and FH' and standard values FL and FH. Then the coil 1 is set to the Lmin and the coil is set to the initial state and the trimmer 4 is adjusted until the oscillating frequency becomes the FH''. Then the coil 3 is adjusted until the frequency reaches the FH while the coil 1 is kept to the Lmin. As the result above, the oscillating frequency at the Lmax is the FL. Then in measuring the frequencies FL' and FH', the trimmer 4 and the coil 3 have only to be adjusted only once each in a high frequency.

Inventors

• 👤 Shojiro Imai
• 👤 今井　祥二郎

Bibliographic Details