The MFJ-17758 is a two band, 80- and 40-Meter center-fed dipole
antenna capable of handling 1500 watts. Its total length is 85 feet.
Each side of the dipole is broken up by a coil that presents a high
impedance at 40 meters and acts as a loading coil on 80 meters, allowing
the antenna to resonate on 80 meters even though it is physically
shorter than a half-wavelength (approximately 130 feet at 3.7 MHz).
Because this antenna acts as a dipole on both bands its impedance is
around 50 to 70 ohms, permitting it to be fed with coaxial cable. The
use of a current balun between the coaxial feedline and the antenna is
highly recommended, to help prevent stray RF from traveling down the
coaxial cable’s outer shield. This is easily accomplished with an
MFJ-915 RF Isolator and a “double male” coaxial connector (MFJ-7702).
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