How to build Transmitter FM 45W with valve

October 12, 2010 - category: FM transmitter


  • Tendency of catering: 220V AC
  • Frequency of emission at FM: 88~108MHz
  • Force of expense: max 45W (without the R3)

Circuit diagram

Transmitter FM 45W with valve-Circuit diagram


  • R1 15KW/2W
  • R2 1KW/10W
  • R3 1KW/10W (for biggest force in the exit you replace with short-circuit).
  • C1 50pF trimmer
  • C2 30pF trimmer
  • C3 22pF/4KV
  • C4, c6, c9 10nF/1KV
  • C5, c7 1nF/1KV
  • C8 100mF+100mF/450V (Double electrolytic)
  • C9, c10 10nF
  • RFC1, rfc2, rfc3 air Inductors: 15 coils diameter 8mm, from wire 1mm.
  • T1 Transformer 220V/6V-1A
  • T2 Transformer of configuration with being first 4 or 8W
  • T3 Inductor with core ferrite (externally it resembles with small transformer but has a turn only).
  • D1 BY127 rectifier
  • Lamp 807 SYLV USA or EL34 or equivalent
  • ANTENNA Simple dipole L/2. (L= wave length)
  • S1 Main switch of catering.
  • S2 Switch of catering of rise (him we close after zestacej' the thread).

Most elements you can him find in a old back-white television with lamps.


  • With the C2 we regulate the frequency.
  • With the C1 we adapt the resistance of aerial (practically him we regulate so that it is heard our voice in the radio as long as you become cleaner).


  • The catering better it does not become at straight line from the network 220V but via transformer 220V/220V of isolation and safety 1A.
  • When does not exist the R3, the force of expense is bigger, but respectively is increased also the hum 50Hz, because the simplicity of designing.
  • The control (Audio In) can become from a kasseto'fwno or other powerful source. If it is microphone it will be supposed precedes amplifier so that it acquires a force of order of 8W roughly.

author: Kyriakos Kontakos
circuit from http://www.electronics-lab.com/

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