Formula Used
Wavelength: wavelength in meters = 300 ÷ frequency in MHz.
Driven full-wave loop: perimeter = 306.32 ÷ frequency in MHz × wire velocity factor × trim factor.
Element sizing: element perimeter = driven base perimeter × (1 + element adjustment ÷ 100).
Triangle dimensions: base = perimeter × base ratio. Each sloping side = (perimeter − base) ÷ 2. Height = square root of sloping side squared minus half base squared.
Spacing: spacing distance = selected wavelength fraction × wavelength. Boom length adds every spacing plus the hardware allowance.
Matching section: quarter-wave length = wavelength × matching line velocity factor ÷ 4. A 75 ohm transformer estimate uses input impedance = 75² ÷ loop impedance.
Delta Loop Beam Construction Guide
Construction Purpose
A delta loop beam turns full wave wire loops into a directional array. Each loop must be sized before the first cut. This calculator helps builders estimate perimeter, side length, boom spacing, and feed matching values. It is useful for temporary field beams, fixed garden arrays, attic experiments, and portable construction jobs where errors waste wire and time.
Planning the Loop
The driven loop is the reference element. Its perimeter is based on frequency and a full wave loop constant. Reflectors are made slightly longer. Directors are made slightly shorter. These length changes shape current phase and push more signal forward. The calculator also handles a custom base ratio, so an equilateral loop or taller triangle can be compared quickly.
Mechanical Layout
Spacing is shown as a wavelength fraction and as real distance. This makes boom planning easier. A small boom allowance is added because clamps, plates, and end caps need room. Side lengths are shown for each element. The height estimate helps plan masts, spreaders, fiberglass rods, and safety clearance.
Feed And Matching
Delta loops rarely land at exactly fifty ohms. Feed point, height, soil, nearby metal, and wire diameter shift impedance. The matching section gives an estimated feed value, a simple standing wave estimate, and a quarter wave transformer length when that option is chosen. Always trim with an analyzer after assembly.
Better Field Results
Cut every loop a little long. Mark the driven element first. Keep both sloping sides equal when the chosen shape requires it. Use nonconductive supports near high current points. Raise the beam to working height before final trimming. Nearby gutters, rebar, roofs, and scaffolds can detune the antenna. Record final dimensions for future builds. Small notes prevent repeated mistakes later.
Safety And Records
This tool gives construction estimates, not a final legal design. Check local electrical safety rules, roof access limits, and radio regulations before mounting anything. Keep the antenna clear of overhead power lines. Label every wire with its element name. Store the calculated table with the project notes. When weather, supports, or feedline change, rerun the numbers and compare the tune again.
Good documentation also helps teams repeat the build. It shows which cuts were theoretical, which cuts were trimmed, and which support parts worked best during each season.
Frequently Asked Questions
What does this calculator estimate?
It estimates loop perimeter, side dimensions, boom spacing, matching length, and general beam performance. It is a planning tool for construction layouts, not a substitute for field tuning with proper test equipment.
Why is the reflector longer than the driven loop?
A reflector is usually made slightly longer so its current phase supports forward gain and rear rejection. The calculator lets you adjust that percentage for your design method.
Why are director loops shorter?
Directors are shortened to pull the main radiation pattern forward. More directors can add gain, but they also narrow bandwidth and make construction alignment more critical.
What base ratio should I use?
Use 33.333 percent for an equilateral loop. Increase or decrease the base ratio to test taller or wider triangles. Keep the shape practical for your supports.
Can I cut the wire exactly to the result?
Cut slightly long. Wire insulation, nearby metal, height, soil, and support materials can shift resonance. Trim gradually after measuring the antenna at working height.
Does the wire diameter change the resonance?
Wire diameter affects bandwidth and tuning slightly. This calculator records diameter as a construction note. Final resonance should still be checked with an analyzer.
What does the quarter-wave transformer length mean?
It is the physical length of matching line after applying velocity factor. A 75 ohm quarter-wave section can help transform many delta loop feed impedances toward 50 ohms.
Is the estimated gain guaranteed?
No. Gain depends on height, ground, spacing, element accuracy, feed placement, and local obstructions. The estimate is a rough planning value for comparing element counts.
Can this design be used indoors?
Small bands may fit indoors, but walls, wiring, metal roofs, and appliances can detune the loop. Use the result as a starting point and test carefully.
How should I place the feed point?
Corner, side, and apex feed points can produce different impedances and polarization behavior. Choose the option that matches your construction goal and matching hardware.
Why is the page listed under Construction?
The tool focuses on build dimensions, material cuts, boom spacing, and layout notes. Those items support practical field construction before final radio tuning.