Loop Antennas

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)

Palomar Horizontal Loop Config 2022 300x202 - Loop Antennas

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

Palomar Vertical Loop Config 300x198 - Loop Antennas

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.

 

440580552 - Loop Antennas
+3

Snap On RF Choke/Isolator - 1/4"/6mm cable, RG-58/59/06/LMR240 - 3-300 MHz, -5/10/15 Bead Option

SNO31-1/4-5
$16.95
In stock
1
Product Details
Brand: Palomar Engineers
MPN: SNO-1/4-5
Effective Frequency Range (MHz): 3-300
PEP Power Rating (watts): same as coax cable rating
Choking Impedance Range (ohms): 5 bead: 500-1000, 10 bead: 600-1800, 15 bead: 1000-2100
Common Mode Attenuation (db): 5 bead: 16-22db, 10 bead: 17-25db, 15 bead: 21-27 db
Estimated Insertion Loss (db): .025
Input Connector Type: none
Output Connector Connector Type: none
Ground Connector (Y/N): none
Enclosure Size (LxWxH inches): none

Use for 1/4″ Cable – RG-58, RG59, RG-6, LMR-240, etc

For 1/4” cables use five FSB31-1/4 split beads for 80-10 meters (3-30 mHz) or ten FSB31-1/4 split beads for 160-10 (1.8-30 MHz) meters or use 15 FSB31-1/4 for even higher choking for 1-10 MHz.

Typical Impedance per split bead: 10 MHz: 100 ohms, 25 MHz: 163 ohms, 100 MHz: 275 ohms, 250 MHz: 275 ohm

Select 10 bead version for 160 meter use. Minimum recommended total impedance is 500 ohms at frequency of interest.

The beads clamp to the cable and may be operated as is for indoor use. However, it is strongly suggested that they be covered to protect the plastic covers from weathering – use electrical tape for best results or heat shrink to ensure longer life. All kits come with instruction manual which covers assembly and application tips.

As you can see from the impedance vs frequency graph, you can very effectively increase the choking impedance by increasing the number of beads on the cable.

Snap On and Slip on Feed line chokes available in sizes to fix cables with outside diameters of 1/4", 3/8", 1/2", 3/4", 1" - check website for other size options.

Save this product for later
Display prices in: USD