DIY 145 MHz Twin Delta Loop Antenna for Ham Radio Operators

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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