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.

 

3498122358 - Loop Antennas
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CUBE Feed Line Choke Unun, 5KW, 1.8-61 MHz, 20-38 dB Common Mode Rejection, Static Bleeder/Ground Option

CU-1-5000SO
$119.95
In stock
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Product Details
Brand: Palomar Engineers
Effective Frequency Range (MHz): 1-61 MHz
PEP Power Rating (watts): 5000
Estimated Insertion Loss (db): .10
Input Connector Type: SO-239 female
Output Connector Connector Type: SO-239 female
Ground Connector (Y/N): none
Enclosure Size (LxWxH inches): 4 x 4 x 2

5000 Watt rated 1:1 CUBE UNUN™

This higher power UNUN utilizes mil-spec coax cable for the windings on a extra large core toroid with coax silver shield and silver braid for low loss. The dielectric is Teflon® insulation for high voltage ratings of 1,900 volts. (A typical 5KW signal at 50 ohms impedance will have a voltage of 500 volts at 1:1 SWR). Wired as a UNUN (CU-1-5000) with SO-239 input and output connectors. Rated 5KW PEP/1500 Watts AM/RTTY/CW from 1.8-30 Mhz, less at 50 Mhz.

If you run RTTY contests or FT8 at 1500 watts output, this is the balun/unun you need – it won’t burn out at heavy 1500 watt duty cycles like other brands rated at 1500 watts (or more). We use these same chokes in our own RTTY station at full 1500 watts output and they have never failed. We use one at the amplifier output and another at each antenna feed point. Works very well on OCF antennas below the 4:1 balun to keep RF current on the antenna and off the feed line. Built like a tank, works like a charm, and priced under the competition – what more can you ask for? THIS IS OUR MOST POPULAR HIGH POWER UNUN!

Choose optional ground lug (on input connector shield) and static bleeder (on input connector center conductor) to bleed off static charges on a continuous basis. (Not a lightening arrestor)

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