PURPOSE: To reduce the higher harmonic disturbance, by providing at the front stage of the 1st mixer a filter which switches in accordance with the frequency of reception for the VHF low band, VHF high band and UHF band, respectively.
CONSTITUTION: The signal received through the antenna 14 is amplified by the wide-band amplifying circuit 15 via the filter circuit 23 and transmitted to the 1st mixer 16. The signal of the 1st local oscillating circuit 17 with variable frequency is supplied to the mixer 16, and the received signal is converted into the signal of a certain 1st IF frequency. This signal reaches the 2nd mixer 19 via the narrow band pass filter 18 that eliminates the image signal and is then converted into the signal of the 2nd IF frequency by the local oscillation signal having a fixed frequency of the 2nd local oscillating circuit 20 to be delivered through the output terminal 22 after amplified by the IF amplifier 21. The filter circuit 23 is used having such characteristics as to attenuate the low band of VHF when receiving the VHF high band and attenuate the VHF band when receiving the UHF, respectively.
| JPS56103932 | HARMONIC FILTER UNIT |
| JPS6041312 | CIRCUIT ELEMENT |
SAITOU TAKESHI
NAGASHIMA TOSHIO
YAMAMOTO SUSUMU
