Calculated Antenna Design
Advanced Yagi TV Antenna Inputs
Example Data Table
| Frequency | Band Use | Directors | Approx. Wavelength | Typical Boom |
|---|---|---|---|---|
| 550 MHz | UHF TV | 5 | 54.51 cm | 70 to 90 cm |
| 650 MHz | UHF TV | 6 | 46.12 cm | 65 to 85 cm |
| 750 MHz | UHF TV | 8 | 39.97 cm | 70 to 95 cm |
Formula Used
The calculator starts with wavelength. The main formula is: λ = 299,792,458 / frequency in hertz. Element lengths are then estimated as a fraction of wavelength. A reflector is usually near 0.50λ. A driven element is often near 0.475λ. Directors are shorter and may be tapered.
Position is calculated from reflector spacing and director spacing. These spacing values are entered as a percentage of wavelength. Boom length is the final director position plus the selected allowance. Gain, beamwidth, and front-to-back ratio are practical estimates. They help planning, but final tuning should be checked with field testing.
How To Use This Calculator
Enter the center frequency for the TV channel or channel group. Choose the number of directors. More directors can improve forward gain. They also increase boom length and aiming sensitivity. Adjust element factors if you have tested dimensions. Use the default values for a fast starting design.
Press calculate to create a full element table. The result appears above the form and below the page heading. Review every element length and boom position. Export the design as CSV for spreadsheets. Export the PDF for workshop notes. Build carefully and keep clear of power lines.
Yagi TV Antenna Design Guide
What This Tool Does
A Yagi TV antenna uses several metal elements on one boom. Each element has a special job. The reflector sits behind the driven element. It helps push more signal forward. The driven element connects to the feed line. Directors sit in front of it. They focus reception toward the broadcast tower.
Why Frequency Matters
Frequency controls wavelength. Wavelength controls element size. A lower frequency needs longer elements. A higher frequency needs shorter elements. This is why one antenna may work well for one channel. It may work poorly for another channel. A wide group of channels may need compromise dimensions.
Element Length Planning
The reflector is usually the longest element. The driven element is slightly shorter. Directors are shorter again. Many builders taper directors by a small amount. This can improve forward gain across the useful range. The calculator lets you control these factors. You can use conservative defaults or custom test values.
Spacing And Boom Size
Spacing changes gain, impedance, and beam shape. Very tight spacing may reduce bandwidth. Very wide spacing may create weaker patterns. A practical design often starts near 0.18λ to 0.22λ. Boom allowance gives extra room for mounting. It also leaves space for clamps and end protection.
Gain And Real Results
Estimated gain is only a planning guide. Real gain depends on material, matching, height, cable loss, and nearby objects. A roof, wall, tree, or mast can change performance. Always test signal strength after installation. Small element trims can improve reception. Use safe mounting methods. Never place an antenna close to electrical wires.
FAQs
1. What is a Yagi TV antenna?
It is a directional antenna with a reflector, driven element, and directors. It focuses reception toward one direction and can improve weak TV signals.
2. Which frequency should I enter?
Use the center frequency of the TV channel you want to receive. For several channels, choose a middle frequency from the target group.
3. Does more directors mean better reception?
More directors can increase forward gain. They also make the antenna longer and more directional. Accurate aiming becomes more important.
4. What is the reflector element?
The reflector is placed behind the driven element. It is usually longer than the driven element and helps reduce signal from the rear.
5. What is the driven element?
The driven element is the active part connected to the feed line. It receives the signal and transfers it to the cable.
6. Are these results exact?
No. They are practical estimates for planning. Final results depend on material, mounting height, cable loss, nearby objects, and tuning.
7. Can I use this for UHF channels?
Yes. Enter the correct UHF frequency in MHz. The calculator will scale the dimensions from the selected wavelength.
8. Why is antenna safety important?
Outdoor antennas can contact power lines or fall during storms. Use strong mounting, safe tools, and proper distance from electrical hazards.