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.
RFI Solution Kits
Palomar Engineers provides a variety of Radio Frequency Interference (RFI) and Electro-Magnetic Interference (EMI) solutions from 100 KHz to 1000 MHz.
We have many RFI solution kits targeting common RFI problems encountered by consumers, broadcast professionals, radio operators, industrial plant managers, marine/ship operators, solar power contractors, etc. For custom individual RFI problems we offer individual ferrite RFI suppression components in bead, snap on and ring topology to fit various wire/cable configurations for AC/DC power cables, coaxial feed line, and device interconnect cables.
Different ferrite mixes suppress different frequency ranges. To select a mix for your interfering frequency see: Choosing a Ferrite Mix
To learn about using ferrites for RFI/EMI suppression check out : RFI Tutorial Center
Get a Copy of Ham Radio RFI Cheet Sheet for all your communication RFI issues!
If you need additional help call 760-747-3343 or email Sales@Palomar-Engineers.com describing your problem.
