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.
Inverted L antenna with radiator and counterpoise for simple installation - choose 80/160 meters and 1.5KW/5KW feed line choke included inside weatherproof enclosure. Separate counterpoise and ground connections
* Complete package - just add coax
* works single band with ease
* can be configured as vertical or inverted L configuration
* Choice of 1.5K, or 5KW PEP rated choke to suit power needs
After many requests we have created a compact, special interface box with internal feed line choke and separate connections for counterpoises (not grounded) and ground connection. The 1:1 choke keeps RF current off the outside of the coax braid and on the antenna where it belongs. The extra choking action also means that the coax feed line will not act as a radiator causing unnecessary RF interference (RFI).
80 M radiator/counterpoise is 70 Feet (you get 1 each) - adjust length to your favorite frequency
160 M radiator/counterpoise is 130 Feet (you get 1 each) - adjust length to your favorite frequency
Antenna is tuned to you favorite frequency by shortening the counterpoise (roll it up or cur length) while keeping the radiator length constant.
Choose 1,5KW PEP or 5KW PEP options.
1.5KW and 5KW are in 4" x 4" x 2" enclosure. 1.5KW is 3 pounds, 5KW is 5 pounds. 2 antenna insulators are included.
ADD CMNF-1500 (1.5KW) or CMNF-5000 (5KW) common mode noise filter at radio end of coax to reduce common mode noise up to 6 "S" units on long coax runs!
