In 1896, Marconi successfully covered a distance of about 3 km using electromagnetic waves. A little later, he established radio contact across water between Lavernock Point, South Wales and Flat Holm Island. The transmitter consisted of a spark inductor coupled to a dipole antenna.
The total length of the dipole rf antenna is:L (cm) = 145/frequency (MHz) .
Radiation pattern and gain of fm dipole antenna
Dipoles have a toroidal reception and radiation pattern where the axis of the toroid centers about the dipole. The maximum gain of a λ/2-dipole is 2.15 dBi.
This is a fm antenna used generally for frequencies between 88 and 108 MHz.
Dipoles have a toroidal reception and radiation pattern where the axis of the toroid centers about the dipole. The maximum gain of a λ/2-dipole is 2.15 dBi.
This is a fm antenna used generally for frequencies between 88 and 108 MHz.
At the receiver side, he used another dipole and a glass tube filled with silver and nickel filings, the so-called coherer. The filings enabled the coherer to act as a ‘defined’ bad contact with the RF pulse energy ‘rattling’ the contact and thus driving the audio amplifiers connected to the output.
The circuit shown here operates on he same principle. Admittedly it does not cover the same distance as Marconi’s extensive radio equipment, but then you do not need to start filing away on the family’s silver cutlery! The transmitter consists of an empty (!) disposable cigarette lighter with a piezo spark mechanism. On the gas nozzle of the empty lighter you solder a 30-cm long,1-mm diameter (20 SWG) solid brass wire which acts as an antenna.
When the spark button is pressed, the antenna briefly radiates electromagnetic energy in the VHF FM frequency band. The effect is easy to verify by holding the transmitter close to an FM radio and ‘firing’ it!
The circuit shown here operates on he same principle. Admittedly it does not cover the same distance as Marconi’s extensive radio equipment, but then you do not need to start filing away on the family’s silver cutlery! The transmitter consists of an empty (!) disposable cigarette lighter with a piezo spark mechanism. On the gas nozzle of the empty lighter you solder a 30-cm long,1-mm diameter (20 SWG) solid brass wire which acts as an antenna.
When the spark button is pressed, the antenna briefly radiates electromagnetic energy in the VHF FM frequency band. The effect is easy to verify by holding the transmitter close to an FM radio and ‘firing’ it!
Radiation pattern and gain of fm dipole antenna
Dipoles have a toroidal reception and radiation pattern where the axis of the toroid centers about the dipole. The maximum gain of a λ/2-dipole is 2.15 dBi.
Dipoles have a toroidal reception and radiation pattern where the axis of the toroid centers about the dipole. The maximum gain of a λ/2-dipole is 2.15 dBi.
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