Stereo superheterodyne receiver with a pilot tone for receiving broadcasting stations in the frequency band from 40-130 MHz based on a TV channel selector (SK-M-24-2). Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / radio reception
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We bring to your attention a simple stereo superheterodyne receiver, with a coding system, with a pilot tone for receiving broadcasting stations in the frequency range from 40 to 130 MHz, based on the domestic TV channel selector (SK-M-24-2). The receiver is very simple and it is important that it practically does not need to be adjusted and the adjustment process will take no more than 5 minutes!
If desired, it can be rebuilt in the range from 40-900 MHz.
Technical specifications
The sensitivity of the receiving path is not worse than ...... 1 μV.
Output power UZCH......4 x 80 W.
Supply voltage no more than ...... 18 V.
Intermediate frequency ...... 10,7 MHz.
The ability to conduct electronic tuning in range!
Disadvantages
The absence of a PLL, but as the operation of the frequency drift receiver has shown, no! if desired, it can be entered from the CXA1538 chip.
Since the conversion is carried out by a non-linear pin diode element, the timbre pumps up a little, but the sensitivity to atmospheric and impulse noise has dropped sharply, the sound is very clear!
(click to enlarge)
The circuit diagram consists of 3 blocks, the first is the TV channel selector, from there you need to pull out unnecessary elements, including the IF circuit and leave the right one. In the diagram, the numbering of parts coincides with the numbering on the selector printed circuit board, so pulling through will not be difficult!
The IF circuit must be placed away from the mixer and local oscillator and carefully shielded!
Setting
We take a ready-made IF circuit (you can buy or solder it from Chinese receivers), pull out the built-in capacitor from it and replace it with two trimmers from 6-40 peak, then turn off the antenna and change the capacitance of the trimmers and find the place where the sound (noise) is the loudest! Next, we solder a 5 cm long wire in place of the antenna with a trimming resistor engine (which is in the base of the transistor to which the antenna is connected), we achieve the best reception of radio stations, then we solder a normal antenna, it depends on your imagination and then ENJOY THE RECEPTION!
Attention! If side harmonics appear in the form of silence when the antenna is turned off and the range is tuned, then it is necessary to shield the IF circuit!
The local oscillator coil is wound with a wire with a diameter of 0,5 mm turn to turn on a mandrel with a diameter of 4 mm and has 5 turns, after winding it must be moved apart in the middle by 2 mm.
The mixer and UHF coils are the same, they are wound with a wire with a diameter of 0,5 mm on a mandrel of 4 mm and has 5 turns and are inserted between the turns of one or another coil! Other tuning blocks are not required!
If the receiver is planned to be used in a car, then the 12 volt stabilizer can be removed.
Author: neitronnaia burya, dendroiduz [dog] mail.ru; Publication: cxem.net
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