Calculate delta loop antenna dimensions for any frequency: total wire length, side length and height, or find the resonant frequency of a loop you built.
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Delta Loop Antenna Formula
For the default empirical full-wave wire-loop basis, total perimeter P = 1005 / f feet = 306.324 / f meters. Each equilateral side is one third of the perimeter:
To solve for frequency instead, the same formula is rearranged:
- L = side length of the delta loop antenna, in meters
- f = frequency, in MHz
- 306.324 = empirical wire-loop perimeter factor in m·MHz (1005 ft·MHz), not the free-space speed
- 3 = number of equal sides; height above the base is L × sqrt(3) / 2
If you enter a frequency, the calculator converts it to MHz and solves for the side length. If you enter a side length, the calculator converts it to meters and solves for the frequency. The result can then be converted to meters, feet, inches, yards, MHz, kHz, or GHz depending on the selected output unit.
Approximate Delta Loop Side Lengths by Frequency
These values use the default 1005 ft·MHz perimeter estimate and side = perimeter / 3. The optional free-space basis instead uses perimeter = 299.792458 / f meters. Actual tuning varies with wire, height, feed point, insulation and nearby objects.
| Band or range | Example frequency | Side length | Side length |
|---|---|---|---|
| 80 m | 3.75 MHz | 27.23 m | 89.33 ft |
| 40 m | 7.15 MHz | 14.28 m | 46.85 ft |
| 20 m | 14.20 MHz | 7.19 m | 23.59 ft |
| 15 m | 21.20 MHz | 4.82 m | 15.80 ft |
| 10 m | 28.50 MHz | 3.58 m | 11.75 ft |
| 6 m | 50.10 MHz | 2.04 m | 6.69 ft |
Example Calculations
Example 1: Find side length from frequency
You want a delta loop for 14.2 MHz.
The side length is about 7.19 meters, or about 23.59 feet.
Example 2: Find frequency from side length
You have a side length of 10 meters.
The calculated frequency is about 10.21 MHz.
FAQ
Is the calculated side length the final cut length?
Use the result as a starting length, not always as the final cut length. Real antennas are affected by wire diameter, insulation, height, feed line, mounting shape, and nearby metal or buildings. It is common to cut the wire slightly long, install the antenna, measure resonance, and trim if needed.
Does feed point location change the side length?
The formula gives the physical size estimate. Feed point location mainly affects impedance and polarization. Feeding a delta loop at a corner, side, or lower point can change how it matches your feed line, but it does not usually change the basic size estimate as much as installation conditions do.
Why does the calculator use MHz and meters internally?
The chosen perimeter factor works with frequency in MHz and length in meters. The calculator converts all input and output units around that calculation. Optional quarter-wave coax length uses 299.792458 × velocity factor / (4 × f) meters; 0.66 is only a default, so use your cable datasheet. Length alone does not guarantee an impedance match.
