Vertical Loop Antenna
Full Wavelength Vertical Loop
HF Antenna Calculator
Using the maximum height and width you have available for your antenna this calculator will evaluate sixty Vertical Loop Antennas; six different antenna shapes for performance on ten HF Bands. Each antenna is checked for; RF efficiency, vertical and horizontal patterns, and VSWR. The calculator will produce a summary report all Single Band Antenna results (even the undesirable) followed by Workable Multiband Antenna summary report.
To use this evaluator fill-in height, width and units then CLICK CALCULATE; the result will be displayed in the below.
More Helpful Information is listed below the tables. Refresh your browser to start over.
Estimated Impedance of Vertical Loop Antenna
The full wavelength loop can be easily matched without a tuner. The round, square, Delta and 1 X 2 Rectangle match at less than 2:1 VSWR using a 4:1 current BALUN at the feed point. Expect to get less than 2:1 VSWR on the whole band for 40M through 10M or a 2:1 SWR Bandwidth of 6% of center frequency. As rectangles and triangles get wide the impedance drops requiring a a 1:1 current BALUN at the feed point causing a decrease in SWR Bandwidth. In most cases the best low profile, easy to hide, stealth, etc. vertical wavelength loop antenna compromise is the 1 X 2 Rectangle because of the pro-DX vertical pattern, good VSWR match and stealth.
Vertical Loop for your next Antenna
Living in a deed restricted community and the confines of those “no antenna” restrictions I still enjoy HF bands. Most of the time I operate on the 20M and 40M bands in CW or digital modes. Disappointing dipole results lead me to try new loop shapes that would blend into my landscape for long term use. While loop antennas will not outperform a beam, they are decent all-around antenna. I found using a vertical full wavelength delta loop is a 12 dB DX improvement over my rather NVIS dipole. The DX improvement is a big advantage of a loop; low takeoff angle for DX and the full loop can be easily matched. The key word is “vertical” as horizontal loops simply do not work very well 10 feet above ground level. In contrast the vertical loop bottom element can be on the ground (but insulated) and still operate with a low take off angle. Do not place the bottom of the loop in the ground; 4 Inches (0.1M) is good. Looking for ways to use a full size vertical loop at home I experiment with any shape that would fit in or around existing structures.
The length of the loop is always one wavelength and the best shape would be round as a circle has the maximum area for a given perimeter. Knowing loops are constructed in many shapes; round, square, triangles or somewhat irregular depending on the support structures available but there performance improves with more area within the loop. This is why are circular full wavelength loop is preferred but difficult to build. My experience has shown the simple to construct delta (equilateral triangle) and rectangular loops produces nice results. I use the Delta for portable operation as only one support is required and the rectangle is gold standard for antenna for fixed sites.
Selecting the shape of the loop will be determined by the location of good supports for the loop. This usually means trees to most people but I have found great success with fences, swimming pool screen enclosures and house walls. The shape of the loop is not fixed by any standard except area inside, my loops have been mostly rectangles or irregular in tall bushes seems work fine. My preference is to loop fed at a corner like a delta. The literature on the feed points indicates the bottom corner of a delta or bottom center of a square/rectangle should produce a lower takeoff angle for better DX. My non-scientific tests of build it and get on the air has not shown any difference with middle, side or 1/3 side feed point. So any irregular looking shape you can construct should work as a real life loop antenna.
When installing a loop around a pool or patio screen enclosure you have some advantages with a large area, small aluminum supports at wide spacing and fiberglass screening. Place the loop inside for low visibility. Any #22 Gauge or heavier wire will handle a 100 Watt transmitter but I recommend #12 AWG THHN to span the 8 to 10 feet between supports and provide high voltage insulation.
Mechanical supports are insulators use for livestock electric fencing painted to match with polymer paint (plastic lawn furniture paint) to ensure dielectric strength. You should have the idea for some locations at your QTH by now. Determine the maximum vertical height available select a loop shape that will work on your site.