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.
DC Voltage Common Mode Noise Filter - Marine, RV, Communications, 600 Volts/30 Amps
DC Common Mode Noise Filter for marine, RV, mobile, portable and fixed station HF operations
The RFI-DC-30 is a common mode noise filter for DC powered equipment up to 30 amps and 600 VDC at 105 degrees C and provides effective dual suppression of common mode current with individual chokes on the positive and negative cables in the HF frequency range from 1-61 MHz (beneficial up to 160 MHz). Very useful for suppressing noise from generators, inverters, battery chargers, solar panels, wind generators, and other noise producing devices sharing the same DC power bus. Simple to install between noise source and noise victim without any modifications to either device.
The enclosure box is a PVC 4″ x 4″ x 2″ weather resistant enclosure with 1/4″ stainless hardware for ease of connection to DC voltage circuits and (optionally) to ground for greater attenuation of the common mode current present on the DC positive and negative lines.
