Calculated Antenna Results
Results appear here after pressing the submit button.
Element Cutting Table
| Element | Perimeter | Side Length | Diagonal | Position From Reflector |
|---|
Advanced Cubical Quad Antenna Calculator
Enter the design frequency, element count, correction factors, spacing, and build preferences. The calculator estimates loop dimensions, wire length, boom length, gain, and element positions.
Example Data Table
This table shows common starting points for cubical quad antenna planning.
| Band | Frequency | Elements | Reflector Increase | Director Shortening | Suggested Spacing |
|---|---|---|---|---|---|
| 20 m | 14.20 MHz | 3 | 5% | 4% | 0.15 λ |
| 15 m | 21.20 MHz | 3 | 5% | 4% | 0.14 λ |
| 10 m | 28.40 MHz | 4 | 4.5% | 3.8% | 0.13 λ |
Formula Used
The driven loop perimeter is estimated with: Driven Perimeter = 1005 / Frequency MHz in feet. The metric value is converted from feet to meters.
The reflector is usually longer than the driven loop: Reflector = Driven Perimeter × (1 + Reflector Percent / 100).
Each director is shorter: Director = Driven Perimeter × (1 - Director Shortening / 100). Extra directors can be shortened further by the step value.
Side length is: Side = Perimeter / 4. Diagonal is: Diagonal = Side × √2. Spacing is based on wavelength: Spacing Distance = Wavelength × Spacing Fraction.
How To Use This Calculator
- Enter your target frequency in MHz or kHz.
- Select the number of quad elements.
- Set reflector and director percentage changes.
- Adjust spacing values in wavelength fractions.
- Add velocity factor and build correction if needed.
- Press calculate to view loop sizes and boom layout.
- Download CSV or PDF results for workshop use.
Article: Cubical Quad Antenna Design Guide
What This Calculator Does
A cubical quad antenna uses full wave loop elements. Each loop has four equal sides. The design often gives strong forward gain, clean patterns, and useful front to back performance. This calculator helps plan the physical dimensions before wire is cut.
Why Frequency Matters
Frequency controls wavelength. Wavelength controls loop perimeter and spacing. A lower frequency needs a larger antenna. A higher frequency needs a smaller antenna. Small frequency changes can still affect resonance, so choose the part of the band you use most.
Driven Loop, Reflector, And Directors
The driven loop is the feed element. It receives power from the transmission line. The reflector is normally placed behind it and made slightly longer. This helps push radiation forward. Directors are placed in front and made shorter. They help increase forward gain.
Spacing And Boom Length
Element spacing is entered as a fraction of wavelength. Common values are near 0.12 to 0.18 wavelength. Wider spacing can change impedance and pattern shape. Short spacing can make tuning more sensitive. The boom length result gives a starting layout for mechanical planning.
Correction Factors
Real antennas rarely match a perfect formula. Wire insulation, support material, loop shape, height, and nearby objects can shift resonance. The velocity factor and build correction fields allow practical adjustment. They help adapt the calculated value to real construction.
Using The Results
Cut elements slightly long when possible. Then trim during testing. Use an antenna analyzer to check resonance, impedance, and standing wave ratio. Keep all sides equal. Keep the frame square or evenly mounted as a diamond. Balanced construction improves the final radiation pattern.
FAQs
1. What is a cubical quad antenna?
A cubical quad antenna uses square full wave loops. It is popular for directional radio communication because it can offer useful gain and strong front to back performance.
2. Why is the reflector longer?
The reflector is longer so it resonates slightly below the driven element. This helps reflect energy forward and improves directional behavior.
3. Why are directors shorter?
Directors are shorter so they resonate slightly above the driven element. They guide more energy forward and can increase antenna gain.
4. Can I use this for any band?
Yes. Enter the desired frequency. The calculator scales dimensions by wavelength, so it works for many amateur and experimental radio bands.
5. Should I cut wire exactly to the result?
It is safer to cut slightly long. Then trim during tuning. Nearby objects, wire insulation, and support materials can change resonance.
6. What spacing should I use?
Many cubical quad designs start near 0.12 to 0.18 wavelength. Final spacing depends on gain, impedance, pattern, and mechanical limits.
7. What does velocity factor mean?
Velocity factor adjusts the electrical length of the loop. Insulated wire or special conductors may need a smaller effective length.
8. Does this replace antenna testing?
No. It gives strong starting dimensions. Final tuning should be checked with an analyzer after the antenna is built and installed.