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Spy Telephone Schematic
This FM spy telephone circuit is mounted serrial with the phone line. When is signal on the wires this transmitter will radiate airwaves thru the wires wich act as anntenna. There is no need for batteries because it got his voltage supply from the phone lines.
There is no need for antenna too, the phone wires [...]
Half wave Dipole antenna
Dipole antenna or half wave antenna are the most used because is easy to build and cost a few bucks but has some drawbacks like little directionality, small gain.
The dipole antenna is build generally like in the picture but it is symmetric and the coaxial cable is asymmetric, that’s why we use a piece of [...]
Yagi antenna 3 elementes
Yagi antenna can be used at transmission or reception but yagi antennas are more used for transmitters.
Yagi antenna or Yagi, is a directional antenna system consisting of an array of a dipole and a reflector and one or more directors.
The dipole in the array is driven, and another element, 5% longer, operates as a reflector. [...]
