10. Application Circuit using the IF count method
The LA1136N and LA1137N can be configured for tuning using either the stop detector or the IF count method. The application
circuits are examples of tuners using the IF count method. The stop detector can be used in any of the application circuits by
making the circuit modifications shown below.
11. Improving Fidelity
Distortion for low-frequency(fm
% 100 Hz), high-modulation signals can be reduced by increasing the capacitance connected to
RF AGC of pins 1 and 2 (LA1136N, LA1137N). However, increasing this capacitance (C2) by a large amount can increase the
AGC response time to an unacceptable level.
12. Loop Antenna Specifications
The recommended loop antennae for the LA1136N and LA1137N are the Korin 42579719100 (LA-1500) and 4257976000
(LA-100A). Note that these are the same antennae previously recommended for the LA1135.
13. AGC ON Level Frequency Characteristics
The frequency at which the sensitivity decreases by –3 dB from the point whenf=1 MHz is as shown below.
Normal
Wideband
LA1136N, LA1137N
37 MHz
24 MHz
LA1135
20 MHz
7 MHz
In other words, in AGC for the main signal, the point at which the AGC sensitivity drops 3 dB is 37 MHz, as shown in the
diagram below. The AGC ON level –3 dB frequencies for narrowband and wideband AGC have been extended from those of the
LA1135 to cover the entire SW3 shortwave band. As a result, the wideband AGC sensitivity is significantly increased and
susceptibility to shortwave interference, reduced. This has been achieved without any increase in dispersion or distortion.
The other pins are the same as those shown in the application circuits.
Ω
RF
AGC
ON
mixer
input
level
–
dB
AGC ON level variation ± 1dBupto30MHz
LA1136 RF AGC ON mixer input frequency – Hz
Narrowband AGC ON level
Antenna
dumping
ON
input
level
–
dB
fr = 1 MHz
Pin 3 input – dB
Wideband AGC ON level
Unit (resistance: Ω, capacitance: F)
LA1136N, 1136NM, 1137N, 1137NM
No. 3507-17/28