WHAT'S THE POINT ?
Here is a version with a power amplifier. A modest power, but comparable to that of other miniature receivers.
We deliver it to you brutally. The antenna signal arrives on C13 / C14, C7 provides tuning, C6 and C5 cover the range of 87.5 to 108 MHz. Resistor R1 reduces the amplitude of the signal sent to the power amp. The latter consists of a TDA 2822 M which offers two amps that we have wired in bridge in order to benefit from a little more power. Another justification: this amp requires only a few external components. Interestingly enough, the power supply requires only three 1.5V components and also works on three Ni-Cd batteries in series, or 3.6V.
The size of the printed circuit is that of a three-element battery coupler R6- Potentiometers and capacitors have been installed on the side, one that receives the switch, in order to be able to install control buttons. We also give you the characteristics of the chokes, (no need to write to the author, it does not provide them ...) The coil L1, once adjusted, will have its turns immobilized by glue (for example Tack Pack Loctite In order to eliminate the feedback effect: the HP vibrates and transmits its vibrations to the local oscillator! The tuning is done by spreading or tightening the turns of the coil until the range is covered.In fact, For P1, we have taken an adjustable one, a small potentiometer log would be preferable (to retrieve, with its button, on an old "transistor" For the button of the capacitor, we took a pinion coming from a toy, pinion glued on the axis of the adjustable capacitor.Other sprocket pinions are relatively close, we have a little miniaturized the realization. For the volume, it is mounted on a screw passing through the central part of the slider. You can optionally install a reduction ratio for tuning, it will be facilitated. The battery holder will be installed against the printed circuit board with milled countersunk screws or after tapping, unless you prefer the double-sided adhesive solution. The HP will preferably be installed on a small speaker cabinet that will enhance the bass response. The very small HP that equips our prototype does not shine by its acoustic qualities ...
LIST OF COMPONENTS
Resistors 1 / 4W 5%
R1: 15 kr - R2: 47kr - R3, R4: 4,7r
C1: MKT 5 mm 0.15 mF - C2: MKT 5 mm 8.2 nF - C3: ceramic 22 nF - C4: ceramic 10 nF - C5: ceramic 22 pF - C6: ceramic 100 pF - C7: adjustable 4-20 Ceramic pF - C8: ceramic pF - C14: ceramic pF - C14: ceramic pF - C14: ceramic pF - C15: C24: MKT 5 mm 0,1 mF - C16: ceramic 2,2 nF - C18: ceramic 220 pF - C19: ceramic 10nF - C20: tantalum 1 mF 10 V - C21: tantalum 10mF 6,3 V - C22: chemical 330 MF 10 V (or 220 mF) - C25: MKT 5mm 10nF
Ci1: integrated circuit TDA 7000 Philips - Ci2: integrated circuit TDA 2822M SGS / Thomson - L1: 4 turns on 5 mm drill, wire 5 to 6 / 10e - L2: 5 turns on drill 4.5 mm, To 6 / 10e - Battery holder, 3 R6, connector, inter, HP 8 ohms - P1: potentiometer 4.7 kr
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