End-Fed Longwire Antenna with a 9:1 UnUn rated at 700 watts,

covering 160 meters through 10 meters, only 124' 6" long.

  

The following tables show the recommended lengths to use for antenna wire based on the bands you wish to cover.

SWR across the HF frequencies will vary based on topography, proximity of nearby structures, configuration of the antenna
wire and your choice of ground or counterpoise.

Installing the antenna as an Inverted L will change the feed point impedance due to top loading and may require changing the
overall length of the wire for best coverage of all HF bands.

Should you decide to install the UnUn in a high location, the use of a counterpoise wire is required as any long wire run to a ground
rod, stake, or radial field will degrade the performance of the antenna.

Please keep in mind this design is intended primarily for use by those living in restricted antenna areas or for temporary or emergency
installations where simplicity and broad HF coverage is important.

Recommended Wire Lengths (in feet) for 9:1 UnUn - 160m through 10m

53    59    72    88.5    98.5    124.5    135    146    162    175

Values in Blue are best overall lengths to use for optimum HF spectrum coverage.


SWR for all lengths should typically be under 2.2:1 and in most cases will be under 1.8:1 for 160m - 10m.

Built in and external antenna tuners will match the antenna on all bands.

Experimenting by slightly by changing the wire length (+ or -) is encouraged to provide the best overall performance for
individual installations.

If you have difficulty obtaining an acceptable SWR on all bands, consider using one of the alternative lengths shown in the table below.

Alternative Lengths (in feet) for both 4:1 and 9:1 UnUns - 160m through 10m

58    71    84    107    119    148    203

If your need for band coverage is limited to 40m through 10m, shorter antenna lengths of 36, 44 and 49 feet may also be used
with the 9:1 ratio UnUn.

By design, UnUns are wound in such a manner that they provide minimal or no RF choking. Although not necessary, a 1:1 isolation / choke
balun may be desirable at the transmitter end of the feedline to stop RF from entering your equipment and reduce receiver noise caused by
common mode currents.

    

Best Installation:

Hang the antenna as a Sloper configuration with one elevated counterpoise. Several different length counterpoises may improve performance.
The length of counterpoise should be a minimum of 30 to 40 feet but not the same length as the antenna wire.

Shorter length counterpoise wires can be used of operation is confined to 40m or higher.

Any counterpoise should be at least 1 foot above ground running away from, or perpendicular to the antenna wire.

Do not ground the counterpoise stud when using a counterpoise(s) or radial field!

Counterpoise wire(s) close to or laying on the ground will couple and become radials and will reduce antenna efficiency.

You may also use the UnUn with no counterpoise or ground if your feedline is at least 25 feet long or longer.

In this configuration, the coax shield will act as your counterpoise and there should be no ground at the UnUn.

With this configuration, there is a high probability of common mode currents on the coax shield, so a good 1:1 choke balun should be installed
in the feedline, at or near the point it enters your shack or operating position.

Good Installation:

Attach a counterpoise stud to a radial field of 8 wires minimum, each 10 to 20 feet long. More is better and will increase the antenna's efficiency.
(Longer length radials are not necessary.)

OK Installation:

Attach a counterpoise stud on UnUn to a good ground rod at the feed point of the antenna.

Although the balun enclosure is weatherproof, connectors are not. Be sure to wrap all coax connections in coax seal or your favorite weather proof tape.
Conductive grease will prevent the brass terminals from corrosion. Ring terminals should be crimped AND soldered and coated with conductive grease.






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