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RECEIVER VHF 26-200 MHz

RECEIVER VHF 26-200 MHz

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  IDEA ELECTRONIC PROJECT

This circuit enables a single super-regenerative receiver and great sensitivity to cover without "hole" frequency range from 26 MHz to about 200 MHz, The tour of these frequencies is, in 5 ranges, with the only change of the main coil. Listening takes place on a listener through an amplifier stage.
The principle of this circuit diagram shows the use of a BF transistor 233 rises and chopper oscillator, the signal from the antenna is applied through a capacitor 47 pf, between the choke coil H and agree L2, which improves the sensitivity of the potentiometer 47 KR allows fine tuning by varying the bandwidth of the antenna circuit. Capacitor 33 pf, disposed between the emitter and the collector, maintains the oscillations. This montage and gives high amplification and high frequency recognizes both that AM FM broadcasts. the choke shock VK 200 blocks mass HF signals. The polarization of the LF 233 is performed by the resistors R 180, and 10 KR 47 KR. and the amplified sensed signal is applied through an adjustable resistor, an amplifier consisting of two transistors 109 BC cascaded. The adjustable resistance KR 47, adjusts the volume and sensitivity. The headset is connected directly to the collector of the last transistor.
For mounting of components, some precautions are necessary, if not respect the orientation of transistors, diodes and chemical capacitor of 47 MF, All components are mounted flat, as close circuit printed, especially the BB diodes 142. the earpiece is directly soldered to the board. The inductor L1 is comprised of a single turn of wire enamel of 8/10 of a diameter of 7mm. The different coils L2 agreement, connected between the terminals A and B are carried out depending on the selected frequency range. the following characteristics:
frequency range coil winding Numbers:

26-40 MHz L2 A 18
40-60 MHz L2 B 8
60 100 MHz L2 C 4
100 to 130 MHz L2 D2
130 to 200 MHz L2 E strap

L2 L2 coils D i are made using enamelled 8/10 diameter wire wound n contiguous turns on tin diameter of 7 mm. L2 E coil consists of a simple strap of enameled wire. also from 8/10 diameter, which short circuits the points A and B. The frequency range change is carried out by replacing the coils 12.
For testing as antenna using a single bonding wire of great length, soldered directly onto the PCB. After carefully performed all the wiring and installation operations, power the receiver under a DC 9V da. We must collect in the ear in the absence of emission, a strong breath. Identical to the sound of a waterfall. Set the adjustable resistance for correct power Turn the potentiometer 47 KR and search for a station. Readjust the resistance KR 47 to eliminate the distortion and get the best listening sensitivity. The receiver is thus in working order, ready to receive transmissions. The reception is significantly improved by the use of an antenna adapted to each frequency range received. For the VHF range, the best reception operates with an antenna tuned in 1/4 wave.
For a more comfortable listening to a speaker, the receiver can be followed by a small amplifier 2 to 5 W about whose input is connected to the headphone output of this circuit.

NOMENCLATURE
-1 circuit imprimé
-1 écouteur
-1 transistor BF 233 = BF 199
-2 transistors BC 109
-2 diodes BB142 = BB105
-1 potentiomètre 47KR LIN
-1 résistance ajustable 47K
-1 résistance 1/4W 100R (marron-noir-marron)
-1 résistance 1/4W 180R (marron-gris-marron)
-1 résistance 1/4W 470R (jaune-violet-marron)
-1 résistance 1/4W 2.2K (rouge-rouge-rouge)
-1 résistance 1/4W 5.6K (vert-bleu-rouge)
-1 résistance 1/4W 8.2K (gris-rouge-rouge)
-1 résistance 1/4W 47K (jaune-violet-orange)
-1 résistance 1/4W 270K (rouge-violet-jaune)
-1 résistance 1/4W 470K (jaune-violet-jaune)
-1 résistance 1/4W 1.5M (marron-vert-vert)
-3 résistances 1/4W 1K (marron-noir-rouge)
-1 condensateur 33PF
-1 condensateur 47PF
-1 condensateur 470PF
-1 condensateur 4.7NF
-2 condensateurs INF
-2 condensateurs 47NF
-3 condensateurs 100NF=0.1MF

-1 condensateur chimique 47MF/25V/RAD.

-1 Im de fil émaillé diam 8/10mm

-1 soudure

-1 fil

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