The 145 MHz Twin Delta Loop Antenna is one of the most efficient and easy-to-build antennas for the 2-meter amateur radio band. With its excellent gain, wide radiation pattern, and stable SWR, this antenna has become a top choice among VHF enthusiasts and home-brew antenna builders. In this guide, we will explore the design, dimensions, feeding method, and performance characteristics of a well-optimized Twin Delta Loop antenna for 145 MHz.
Understanding the Twin Delta Loop antenna Design
A Delta Loop is a closed triangular loop antenna. When two identical triangular loops are placed opposite each other and fed at the center, the design becomes a Twin Delta Loop.
This configuration provides:
- Higher gain
- Better directivity
- Lower noise
- Stable SWR across the 2-meter band
- Improved radiation efficiency compared to a simple dipole
The Twin Delta Loop behaves like a directional, bi-cone-style loop antenna, ideal for both base stations and portable communication setups.
Dimensions for 145 MHz
The optimized dimensions for 145 MHz are as follows:
- Slanted edges: 760 mm
- Vertical height: 701 mm
- Gap at feed point: 40 mm
- Coax feed: 50-ohm coax (RG-58 or RG-213 recommended)
- Support structure: Non-metallic frame recommended
- Top reference point: A
- Bottom reference point: B
These measurements ensure resonance around 144–146 MHz, covering the entire VHF ham radio 2-meter band.
Feeding Method
The antenna is fed using 50-ohm coaxial cable, directly connected at the 40 mm feed gap:
- Center conductor → connects to the upper triangular loop
- Shield/ground braid → connects to the lower triangular loop
For best performance:
- Keep the coax at a right angle as it leaves the feed point
- Use a choke balun (4–5 turns of coax, 10–12 cm diameter) to reduce RF currents on the feedline
- Ensure both loops are identical for proper symmetry and gain
Construction Tips – Twin Delta Loop antenna
- Use 2.5 mm to 3 mm copper wire or aluminum rods for the loops
- A PVC frame is ideal for holding the structure
- Maintain equal dimensions on both sides to avoid SWR mismatch
- Ensure the triangular loops remain flat and do not warp
- Mount on a non-metallic mast to avoid detuning
- Keep the antenna away from metal structures, walls, or water tanks
Whether you are a beginner or an experienced ham operator, this antenna provides a perfect balance of gain, simplicity, and reliability. With proper construction and tuning, it can outperform many commercial VHF antennas while costing almost nothing to build.
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