FM TRANSMITTER AND BROADCASTING SYSTEMS
STACKED DIPOLE ANTENNA
The double stacked dipole has the benefit of 4.7dBi of gain and broadband operation. This is achieved using a specially designed splitter box to feed each dipole antenna with the correct RF signal phase. Providing the antenna is mounted correctly the SWR is less than 1.8 across the whole band from 87.5 to 108 MHz. This antenna system never needs tuning, just put your transmitter on any frequency from 87.5 to 108 MHz and switch on.
Normally the dipole system clamps as high off the ground as possible to a mounting pole of at least 4 meters in length and 50mm in dia which you need to provide and engineer yourself.
The RF field strength directly below this antenna is lower than that of a single dipole. The built in balun provides a truly unbalanced input and prevents any RF currents traveling down the outer of the feeder cable. This combined with the low field strength below the antenna reduces the chances of audio and TV interference considerably and maximises RF power to the horizon.
4.8dBi Gain at Band Centre
SWR less than 1.6 from 87.5 to 108 MHz
20 MHz Bandwidth
Aluminum and ABS Construction
50 ohm unbalanced input (SO-239 socket)
Coaxial line losses can be considerable at 87.5 - 108 MHz. For long runs use a good quality cable such as LMR400 or equivalent for connecting the antenna system to the transmitter.