LA1245 datasheet(4/11 Pages) SANYO

4 / 11 page

LA1245

No.737-4/11

Notes on LA1245 usage

1. When suddenly tuned to a broadcasting station of intermediate or high field strength, a large current of high frequency

flows into the signal meter circuit, causing the local oscillator malfunctions and abnormal noises.

To eliminate this :

· Use R208≥240Ω for manual tuning type.

· Use R208≥82Ω, and use the local oscillation coil at the 1/3 tap (except SW) for electronic tuning type (which uses a

narrow band filter).

2. Use the bias on the condition RF VCC≤IF VCC, since abnormal noise levels might be caused when detuning a strong

input on the codition RF VCC>IF VCC.

3. Use the signal meter driving output (VSM) at VSM≤VCC–2 (V) to avoid saturation caused by VCC.

4. Use 1/2 or more tap of LW and MW oscillation coil to improve S/N and the detuning characteristics of the distortion

ratio.

5. Use the full-tap of SW oscillation coil, to allow the sag in oscillation power by the decreasing of Q.

6. Avoid the coupling of the antenna tuning circuit and the local oscillating circuit so as not to leak the local oscillation

into the antenna tuning circuit.

7. Connect the detection capacitor C113 between pin 13 (output) and pin 14 (VCC) to avoid the leakage of the IF signal

into the GND line. Connection between pin 13 and pin 12 (GND) increases the tweet interference and deteriorates the

usable sensitivity.

Moreover, depending on the positions of C113 and the bar antenna, higher harmonics having twice or three times the

frequency of the IF signal may pass into the antenna and cause tweet interference, and in extreme cases oscillation

might be cause. To prevent this :

· Shorter lead wires and connect them near 13 and 14 pins.

· Place C113 far from the antenna.

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