Three of these amplifiers are used in series to build the 455 kHz IF amplifier. AGC voltage comes from the AGC Circuit
http://www.pan-tex.net/usr/r/receivers/secifamp.htm
Primary winding has 18 turns, the secondary winding has 4 turns. The capacitors across the IFT primaries are 82pF. The -6db bandwidth is about 2.5KHz.
http://homepage.tinet.ie/~ei9gq/ifamp.html
Based on Philips TDA7000 receiver chip. It is tuned with a BB105 varicap diode in the 13MHz IF band.
http://jcoppens.com/sat/rx/tda_if.en.php
IF amplifier filters are LC resonator stages separated by individual stages of amplification. The principle is called synchronously tuned filters stages. In if amplifier filters there can be any number of resonators per individual stage.
http://www.electronics-tutorials.com/filters/if-amplifier-filters.htm
Design and implementation of an IF-Amplifier for FM-receiver PMR446 operating at 446 MHz. IF-amplifier realized with discrete components works with the center frequency of 21.4 MHz.
http://www.ele.tut.fi/teaching/74601/Ryhmien_raportit/pdf/08.pdf