Calculator Inputs
Formula Used
The calculator starts with wavelength. The formula is wavelength = speed of light ÷ frequency. Frequency is converted from MHz to Hz before calculation.
Loop perimeter = wavelength × velocity factor × element factor. Square side = loop perimeter ÷ 4. Diagonal = side × √2. Center to corner support length = diagonal ÷ 2.
Boom spacing = wavelength × spacing factor. Total wire equals all loop perimeters plus the selected allowance percentage.
How To Use This Calculator
Enter your operating frequency in MHz. Keep the velocity factor near one for bare wire. Use a lower value when insulation or construction changes the electrical length.
Adjust reflector, driven, and director factors if you follow a known design. Enter boom spacing values as fractions of wavelength. Press calculate to show the result above the form.
Use the CSV file for spreadsheet work. Use the PDF button for a simple printable field sheet.
Example Data Table
| Band Example | Frequency MHz | Velocity Factor | Reflector Factor | Driven Factor | Director 4 Factor | Typical Boom λ |
|---|---|---|---|---|---|---|
| 20 meter design start | 14.200 | 0.98 | 1.05 | 1.00 | 0.93 | 0.805 |
| 10 meter design start | 28.400 | 0.98 | 1.05 | 1.00 | 0.93 | 0.805 |
| 6 meter design start | 50.125 | 0.98 | 1.04 | 1.00 | 0.92 | 0.775 |
What This Calculator Does
A six element cubical quad is a directional loop array. It has one reflector, one driven loop, and four directors. This calculator turns frequency into practical loop and boom dimensions. It gives wavelength, element perimeter, side length, loop diagonal, spacing, boom length, wire length, and a simple gain estimate. It also lets you adjust scale factors. That makes it useful for common designs and custom experiments.
Why Dimensions Matter
A cubical quad uses full wave loops. Small errors can move resonance and change front to back behavior. The driven element is often close to one wavelength in perimeter. The reflector is usually larger. Directors are usually smaller. Spacing controls coupling between loops. Good spacing improves forward gain. It can also reduce rear radiation. The final antenna still needs real world trimming. Wire insulation, frame material, height, and nearby objects change the exact result.
Formula Used
The base wavelength is found from the speed of light divided by frequency. A velocity factor can shorten the electrical length. Each loop perimeter equals wavelength multiplied by its element factor and velocity factor. Each square side equals one quarter of the perimeter. The diagonal equals side length multiplied by the square root of two. Boom spacing equals wavelength multiplied by each spacing factor. Total wire equals the sum of all six loop perimeters plus the extra allowance.
Building Notes
Use these values as a starting layout. Cut wires slightly long when possible. Build a strong spreader frame. Keep opposite corners square and stable. Measure each side after tying the loop. Feed the driven loop with a suitable matching system. A quarter wave matching section, current balun, or gamma match may be used. Check SWR at low power first. Trim the driven loop in small steps. Keep notes after each change.
How To Use Results
Enter the frequency, velocity factor, element factors, and spacings. Press calculate. Review the result above the form. Compare all element dimensions in the table. Download a CSV file for spreadsheets. Use the PDF button for a printable report. Save several versions when testing different bands or boom lengths.
The calculator also helps students connect radio formulas with a real antenna structure they can inspect and improve.
FAQs
What is a six element cubical quad antenna?
It is a directional loop antenna with six square loop elements. It usually has one reflector, one driven element, and four directors mounted along a boom.
Why is the reflector larger than the driven loop?
The reflector is larger so it resonates slightly lower. This helps push more energy forward and reduce radiation behind the antenna.
Why are directors smaller?
Directors are smaller so they resonate slightly higher. Their size and spacing help shape forward gain and beam direction.
Can I use insulated wire?
Yes. Insulated wire may shorten the needed physical length. Use the velocity factor field to adjust the electrical length before cutting.
Are gain values exact?
No. Gain values are estimates for planning. Real gain depends on height, ground, matching, construction accuracy, and nearby objects.
What does center to corner mean?
It is half the square loop diagonal. Builders can use it as a guide for spreader arm length from the loop center.
Should I cut the wire exactly?
Cut slightly long when possible. Then tune carefully. It is easier to shorten a loop than to repair one cut too short.
Can this calculator be used for any band?
Yes. Enter the desired frequency in MHz. The formulas scale the antenna dimensions for that selected operating frequency.