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This is a simple 27MHz FM-CB receiver built with TCA440 for listening CB ( citizen’s band ) transmissions with FM (frequency modulation). The selection is made with ceramic filters. This 27 MHz receiver works with an intermediary frequency of 455 kHz. The input filter is 27 MF type, so we obtain an acceptable attenuation of the mirroring frequency.
The 10 meters 27MHz CW radio amplifier is equiped with VN66AF transistor produced by Siliconix wich has some advantages: its cheap, great dielectric insulation and high gain. Here we use VN66AF as an rf amplifier for 10m band (26 … 30 MHz ).
NBFM or Narrow Band Frequncy Modulation is used in this 27 MHz fm transmitter circuit schematic. This circuit is an application by Motorola MC2833 – VHF transmitter with FM modulation and narrow band in a single chip.
The output power is 10mW (+10 dBm) and the coverage is 10 – 20m.
P1 is used to adjust microphone amplification and P2 to adjust the deviation. Remember that this 27MHz fm transmitter use NBFM with maximum 5KHz deviation, this mean you have to use an nbfm receiver to obtain enough audio level.
