Remote Circuit Diagrams

UHF Remote Control Receiver Schematic Circuit Diagram

Receiver for UHF Remote Control Transmitter

Designed primarily for use with the UHF remote control transmitter discussed in the previous article, this receiver employs a super-regenerative type with an active RF amplifier, denoted as T1. The antenna signal is introduced through a BNC socket and undergoes tuning via trimmer C4 in the input circuit.

Superregenerative Stage and Oscillator Locking

The amplified RF signal is then directed to the superregenerative stage, facilitated by transistor T2. Although the oscillator is not strictly tuned, it effectively locks onto the amplified RF signal transmitted through coupling capacitor C7. Extraction of the low-frequency modulation component from the oscillator signal is achieved through a low-pass filter consisting of R6-C11-R7-C-12-R8-C13. The demodulator output signal level ranges from 50 to 800 mVpp, necessitating additional amplification before it can be applied to a digital input.

UHF remote control receiver Schematic diagram

UHF remote control receiver Schematic diagram

Construction Details of RF Amplifier Inductors

The inductors used in both the RF amplifier input and output are crafted from 1mm silver-plated wire, with their lengths clearly specified in the component overlay. Positioned approximately 3 mm above the board surface, these wires are integral to the circuit’s functionality. It’s noteworthy that the stator terminal of C4 is bent upward and soldered directly to the input inductor. Similarly, junction C6-C is soldered “in the air,” directly onto the hot end of the inductor wire. Inductor L1, composed of 12 turns of 0.6-mm-dia. enameled copper wire, features an internal diameter of 3 mm. Chokes L2 and L3 each consist of 4 turns of 0.2-mm-dia. enameled copper wire threaded through a 3 mm-long ferrite bead.

Placement of SMT Components and Circuit Screening

Capacitor C8, a surface-mount technology (SMT) type, is affixed on the solder side of the board, along with the BFG65 and the BF980 transistors. The type indications on the transistors are legible from the component side of the board. The super-regenerative section of the circuit, delineated by dashed lines on the component overlay, requires screening from the rest of the components. To achieve this, soldering a 20-mm-high tin plate box directly to the PCB copper surface is recommended.

UHF remote control receiver Schematic diagram

UHF remote control receiver Schematic diagram
Resistors:
  • R1 = 330 kΩ
  • R2 = 150 kΩ
  • R3 = 680 Ω R4, R6 = 3.9 k.Q. R5 = 120 IcS2 = 10 kS/R8 = 33 Ic.C2 R9 = 8.2 IcE2
Capacitors:
  • C1 = 470 uF, 16 V radial
  • C2, C5, C9 = 330 pF ceramic
  • C3 = 1 nF, coffin-style leadless ceramic
  • C4, C6 = 10 pF trimmer
  • C7 = 12 pF, ceramic
  • C8 = 3.9 pF (surface mount)
  • C10 = 1 uF, 16 V, radial
  • C11 = 10 nF
  • C12 =  3.3 nF
  • C13 = 1 nF
Semiconductors:
  • T1 = BF980 or
  • BF966
  • T2 = BFG65
  • D1 = 1N4148
Inductors:

Construction details are given in the text: 2 off 3-mm ferrite beads 0.6 mm dia. enamelled copper wire 0.2 mm dia. enameled copper wire, 1 mm dia. silver-Plated copper Wire

Miscellaneous:
  • K1•K2 = BNC socket

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