Abstract :
With the development of communication technology encourages people to create a
communication system that is easy to use with a relatively affordable price, including radio
telecommunication systems, with a wide range and it is cheaper than using cable
communications systems. In a radio transmitter, there are five main parts: the encoder,
modulator, power amplifier, antenna, and power supply. One important part of a radio
station is the antenna. The antenna is a very important component in radio
telecommunication system because it serves to transmit or receive radio waves. Antenna as
a transmission medium for wireless devices that utilizes free space as a medium conductor.
In STT Telematika Telkom Purwokerto unavailability antenna as radio transmitters so that
the author makes an design of omnidirectional antenna for transmitter Frequency
Modulation. In this final task antenna made is omnidirectional antennas 5/8λ.
Omnidirectional Antenna 5/8λ is Antenna with composed of vertical elements whose length
is 5/8 lambda and horizontal elements 1/4λ in length and must be equipped with loading as
a series of matching his device. Measurements were taken using a measuring instrument
Power & SWR meter, dummy load and Spactum anlyzer. The results of the measurement
antenna is an antenna can work at a frequency that has been set is 107.7 MHz with VSWR
value of 1.3. Has a radiation pattern that is suitable for emitting electromagnetic waves in
all directions, or by 3600 with 50 Ω impedance and a gain of 6.15dB. beam antenna range
of 3 Km.
Keywords: FM, Omnidirectional, 5/8λ, 107.7 MHz.