Owners of TVs with ZUSTST the submodule radio SMRC-2 living in the area uncertain reception, offer a simple way increase the sensitivity of APCI (and TV in General) in 1.5-2 times by replacing the values of a few resistors.
The analysis of the scheme the differential amplifier submodule radio SMRC-2, collected on the transistors VT2 and VT3, using techniques taken from [1] shows this cascade amplifies the signal and serves as apparently only to obtain a vapour phase the voltage required for normal operation IC D2 type differential CUR entrance. The schema snippet SMRC-2 shown in the figure. The numbering of elements corresponds to the scheme of the manufacturer, and the new resistor values. Gain cascade (estimated) with these values equal to 5, but the real is somewhat lower due to stray tanks installation and shunt operation IC D2.
Hams, loving to experiment and decided to repeat this scheme, I advise you to try to reduce the values of R9 and R13 (they should be identical) This will increase the gain, however, can lead to the excitation of UPCI. Now from theory to practice. In Lozova my MB antenna type 3-element "wave channel" aimed at Lozovaya repeater "Sideways" took the signal UT-1 (2 channel) from the town of Raisins (a distance of about 90 km). To rework the image was black and white, the sound from loud noises. After the alteration - the sound clear, the image is colored with light "snow". In conclusion I want to say that further enhancement of the sensitivity the TV probably due to the replacement of selectors channel SC-M-24 and SC-D-24 more modern all-wave SC-41, SC-M, etc.
Literature:
Author: G. W. Velichenko; Publication: www.cxem.net