Loop antennas may be constructed in many forms including horizontal full wave loops in square, rectangle or triangle (delta) shapes. They can also be in the vertical plane and are most often in the same shapes with the delta being very popular as it has both vertical and horizontal polarization. The impedance at the loop resonant frequency is approximately 100 ohms but will very slightly on harmonics. Loops are “quiet” antennas compared to verticals and dipoles and are omni-directional. The also exhibit gain on harmonic bands. Once you try a loop antenna you will know why they are so popular with old timers but still a secret to newcomers. Shown below are some typical designs:
Full Wave Horizontal Loop Antenna (a.k.a Skyloop)
This antenna is horizontally polarized and should be mounted as high as possible but works well at low heights of 10-30 feet. They are quieter than a dipole or a vertical, have a broader bandwidth and will usually out perform a dipole antenna.To determine the approximate circumference in feet of a full wave loop antenna use the formula:
1005/Freq in Mhz = length in feet.
The feed point impedance of a full wave loop antenna is theoretically in the vicinity of 120 ohms and requires a 2:1 impedance transformer (for single band loops or a 4:1 balun to match on multiple bands) with 50 ohm line. You will also need a feed line choke or better yet, just get the Hybrid 4:1+1:1 in a single box.
Vertical Delta Loops
Vertical delta loops can be oriented several way but the most popular is to have the “pointy” end at the top (usually a single support) and the lower horizontal ends just out of reach of humans and animals. Best feed point is 1/4 wavelength (246/f(mhz)) from the top point down one side. Vertical delta loops use the same 2:1 baluns as the horizontal loops or 4:1 for multi-band operation.
Bullet End Fed Long Wire (EFLW) Antenna Wire Kit for end fed long wire antennas - choose 41, 71, 111, 155, 173, 203, 268 foot lengths complete with end insulator, #14 Insulated stranded copper wire and spade lugs and heat shrink for lugs for attachment to an optional Bullet 9:1 unun.
Insulators are a very stealthy, strong, pair of 2 PVC, 2 1/4" long. 1" wide. 1 1/8" hole separation wire antenna insulators and may be black, gray or white depending upon inventory
See related products for 9:1 transformers from 100 watts to 5KW, 9:1 toroid kits, and feed line chokes.
For a complete installation you will need 9:1 unun, wire kit, appropriate length of coax, and feed line choke (SOFLC is easiest to use and change position as you tune the antenna).
Bullet Antenna Length - feet (41, 71, 92, 111, 155, 173)
Corresponding Counterpoise length feet (16, 42, 90, 37, 95, 80) - place feed line choke on coax at this measured length from 9:1 unun
TECHNICAL NOTE: If you are building your own End fed Long Wire antenna, don't forget the end fed coax choke (or equivalent counterpoise) which is required to make the antenna operate correctly! End fed coax choke part numbers are SOFLC, EFFLC-240
