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An 80-10 end-fed half-wave antenna can be a very good performing part of an HF station. But its performance depends heavily on a well-designed and carefully constructed 49:1 unun, which matches the long wire impedance to within tuning range of operation. But the perfor-mance of an end-fed antenna is also very dependent on height above ground.
For it's simplicity and small dimensions is very popular for portable or SOTA activities, and also as a static-mobile antenna. This Mini 49:1 UnUn can be used also as the base point of a vertical dipole antenna with its half wave length. MULTIBAND ANTENNA.
This project assembles a 49:1 ferrite-core (“FT”) type #43 transformer that matches 50 ohm input to 2500 ohm end fed antenna. It is optimized for 3.5/7/10/14 MHz but will work reasonably well on all amateur bands from 80 meters thru 10 meters with a 135 foot length of wire and a short connection to ground.
Ham Radio HF/VHF Antenna Lengths Chart. Here is a handy chart for determing 1/4 wave verticals, 1/2 wave dipoles, and full wave loop lengths. All antenna lengths in the information below are in feet and are the results based on the standard formula of 468 / FMhz = total length in feet.
If the transformer is used with an external tuner in conjunction with a single wire antenna typically 130-135 feet in length, power should be reduced on those bands that show an SWR above 1.6 to 2:5 without the tuner.
For best results, use the longest wire shown on the table that will fit your installation constraints. Installing the antenna wire as an Inverted L can change the feed point impedance and may require tuning (changing overall length of the wire) for best coverage of all HF bands.
Recommended wire lengths and Installation Notes for Unun models 4932, 4935, 9130, 9132 & 9135. Table shows typical SWR relative to installed wire length. SWR will vary based on topography, proximity of nearby structures, configuration of the antenna wire and choice of ground or counterpoise.
