Calculate a delta loop antenna’s missing side length or resonant frequency from one known value in meters, feet, inches, yards, kHz, MHz, or GHz.
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Delta Loop Antenna Formula
The calculator uses the following relationship between frequency and side length:
L = 300 / (f * sqrt(3))
To solve for frequency instead, the same formula is rearranged:
f = 300 / (L * sqrt(3))
- L = side length of the delta loop antenna, in meters
- f = frequency, in MHz
- 300 = approximate speed of radio waves in free space, expressed as meters per microsecond
- sqrt(3) = square root of 3, approximately 1.73205
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 same formula as the calculator. Actual tuning may vary because wire type, height above ground, feed point, insulation, and nearby objects can shift resonance.
| Band or range | Example frequency | Side length | Side length |
|---|---|---|---|
| 80 m | 3.75 MHz | 46.19 m | 151.54 ft |
| 40 m | 7.15 MHz | 24.22 m | 79.45 ft |
| 20 m | 14.20 MHz | 12.20 m | 40.03 ft |
| 15 m | 21.20 MHz | 8.17 m | 26.80 ft |
| 10 m | 28.50 MHz | 6.08 m | 19.95 ft |
| 6 m | 50.10 MHz | 3.46 m | 11.34 ft |
Example Calculations
Example 1: Find side length from frequency
You want a delta loop for 14.2 MHz.
L = 300 / (14.2 * sqrt(3))
L = 12.1967 m
The side length is about 12.20 meters, or about 40.03 feet.
Example 2: Find frequency from side length
You have a side length of 10 meters.
f = 300 / (10 * sqrt(3))
f = 17.3205 MHz
The calculated frequency is about 17.32 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 constant 300 works directly with frequency in MHz and length in meters. If you enter kHz, GHz, feet, inches, or yards, the calculator first converts the input to MHz or meters, applies the formula, and then converts the result to the output unit you selected.
