AGC s A244D (TCA440)

A very successful AGC circuit is the ND6T, however, other connections may be appropriate in some designs. the described AGC circuit uses A244D (TCA440), or integrated circuit for receivers up to 30 MHz. We will use only a part of it for AGC, which is a four-stage MF amplifier and its control circuit. The range of regulation can be up to 60 dB, which is really a lot. He will tell more about this integrated circuit datasheet.

The principle of AGC is simple. An NF signal is fed to input A244D, which is intensifying. The output signal is rectified by a diode and fed back to the gain control circuit of the first three stages of the amplifier in A244D. At the same time, with the values ​​of variable resistance and capacitor C5, we create the possibility to set the level of regulation and the time constant..

Probably the biggest disadvantage of the A244D is, that the MF part of this integrated circuit operates only at lower frequencies, do 2 MHz. The idea outlined here processes the NF signal, but we can also use it to control the MF frequency, e.g.. 455 kHz or similar. To terminal no. 10 it is also possible to connect an indicator S-meter.

Spring:

[1] A set of lectures from the nationwide seminar for radio amateurs of Zväzarm Tatras 1983, Use available ICs in amateur radio practice

[2] MKARS80 transceiver OM0AAO