DELTA LOOP HF BEAM Muli-Element

Diagram illustrating the setup of a 5-element HF Quad Delta loop beam, showing the arrangement of wires and feed-lines suspended on ropes between two supports.

Antennas.....before Amplification

I possess a 40-meter wire Delta-loop multi element beam that originally started as a 6-element setup. This design is notable for its wide spacing, an important feature that enhances the antenna's performance. However, following thorough testing and analysis, I opted to simplify the design by decreasing the number of elements from six to four. This change not only made the antenna's structure more streamlined but also improved its overall efficiency. The new configuration closely resembles a quad beam antenna, recognized for its excellent directional properties and gain.

The antenna is fixed in one direction, which is a strategic choice that allows for focused signal transmission and reception. This fixed orientation is achieved by hinging the antenna from a catenary line that runs between two tall towers. The use of a catenary line is particularly beneficial as it helps to maintain the tension of the wire, ensuring that the antenna remains in optimal shape and alignment, which is essential for effective performance.

The HF Delta loop beam will beat a yagi every time

An actual photo view from the top of the tower looking at the 40-meter wire Delta Loop multi element beam, the Delta loop feeder and Balun on a catenary cable at a height of 100 feet

During my experimentation with the original 5-element setup, I conducted both practical tests and theoretical modeling, with assistance from WA7ARK, an expert in antenna design and modeling. Far field survey testing was performed on site, as this array is installed at the K0UO & RSI Corp far field antenna test range. The results from both the empirical testing and the simulations indicated that the sixth and fifth elements, despite being widely spaced, exhibited minimal current flow. This lack of current in the fifth element suggested that it was not contributing effectively to the antenna's overall performance. As a result, I realized that taking out this element would not only streamline the design but would also lower the wind load.

Overview

Delta Loop beam antenna is essentially a type of quad (loop) antenna, specifically a triangular variant of a full-wave loop element.

Polarization & Feed: Feeding point affects polarization (horizontal or vertical) and takeoff angle in both.

Both are full-wave loop antennas (perimeter ≈ 1 wavelength) and belong to the broader family of parasitic loop arrays.

Testing of both antennas in the air, shows the Delta with .2 dB to .4dB more gain. However modeling gives the Quad +.3 to .5 dB more, our tests in the far field show that this is do to the Deltas over all higher height above ground, the Quad has the lower part of its wire closer to the ground, so it has ground loss and a higher take of angle.

Note, this K0UO blog uses dB gain, not dBi when providing antenna gain data, don't be fooled by dBi.

The Real-World Difference: The difference is only about 0.3 dB. In the real world, human ears cannot detect a difference

Both antennas excel here compared to standard dipoles or verticals because they are closed loops, making them less susceptible to local man-made electrical noise (QRM).

• Polarization: On both antennas, your feed point determines your polarization.

  • Feeding a Delta Loop at the center of the bottom wire yields horizontal polarization; feeding it one-quarter wavelength down from the apex on the side yields vertical polarization.

  • Feeding a Quad at the bottom corner yields horizontal polarization; feeding it at a side corner yields vertical polarization.

  • I feed mine at the top, using the top support line to hold the coax. Symmetrical Radiation Pattern

    Feeding at the top apex creates a highly symmetrical current distribution down the two sloping legs of the triangle. This results in a clean, broadside radiation pattern perpendicular to the plane of the wire loop, with excellent front-to-back or front-to-side rejection if configured as a beam.

    . Slight Loss in Low-Angle DX Gain

    Compared to feeding a point-down Delta Loop at the bottom, top-feeding can cause a slight reduction roughly 0.3 dB in ultra-low-angle radiation. Because the maximum current concentration is at the top feed point rather than closer to the earth, the ground interaction changes slightly, occasionally yielding a marginally higher takeoff angle in the model. For most operators, this minor theoretical difference is completely unnoticeable in daily operation. But the slight loss in the model, really shows up as gain, on the real world test on the antenna range of +.2dB.

    
    

  • So I choose a top-feed configuration which has nothing to do with physics and everything to do with structural engineering:

    • Easy Coax Routing: If your Delta Loop is suspended from a high catenary line, tower, or tree limb, the feed point is already at the highest, most secure structural support anchor.

    • No Hanging Cable Strain: You can bond your coaxial cable directly to the main support rope or messenger cable. This removes the physical weight and wind-yank of a heavy coax drop dangling from the center of a floating bottom wire, preventing wire stretching or connection failures over time.

  • Top feeding is a win win for my setup.

K0UO emphasizes the scientific method: model → build → far-field test → refine

The decision to move to a 4-element configuration has proven to be beneficial, as it maximizes the performance of the antenna while minimizing unnecessary complexity. The remaining elements are now better utilized, and the overall gain and directivity of the antenna have improved as a result of this thoughtful redesign. This experience underscores the importance of careful testing and modeling in antenna design, as it can lead to significant improvements in performance and functionality.

So a wide spaced design, using 4 elements is the way to go, with a tested 13.65 dBi of gain on the 100 foot height.

The Delta Loop design was selected due to its higher gain, improved front-to-back ratio, and because it didn't necessitate a different setup than hanging an inverted V wire Yagi-type beam.

Diagram illustrating a 3-element loop antenna setup, highlighting the driven element with triangular configurations. The reflector is depicted as 5% longer, while the directors are progressively shorter by 4%. The feed point is attached to an insulated block, with support ropes at each lower corner. Side view shows reflector, driven, and director arrangement.

I did feed it at the top, which cost me a little of the low angle gain (.5), but I wasn't really concerned about that, but only the ease of feeding, the coax was bonded to the support line, making it easy.

Unlike a Quad beam, the Delta Beam the loop only needs 2 ground guys per element instead of 3 or 4 for a Quad.

WA7ARK Model below

Azimuth and elevation patterns of a K0UO 40 meter 4-element Delta Loop Beam, showcasing dBi performance .Comparison of antenna radiation patterns at 7.150 MHz, showing azimuth plots for a 23-degree elevation. The first plot contrasts the performance of 3-element (blue) and 4-element (red) designs, while the second plot details the 23-degree elevation pattern with top gain at 13.65 dBi. Key specifications include element circumferences and distances between elements.

Polar plots illustrating the azimuth radiation patterns at 23-degree elevation for antenna configurations. The top image compares the best 4-element (red) and best 3-element (blue) designs at 7.150 MHz, while the bottom image shows a detailed view of the azimuth pattern for the 4-element configuration at 23 degrees.

4 Elements has good parasitic coupling from DEs

So what happens if you add more elements?

It is a waste, on this beam using wire elements, see the data below.

 WA7ARK Model, This array is fed at the apex of the Driven Element. Optimized for forward gain (weight=3 most important), then f/b and f/r (weight=2), and finally for Swr(50) (weight=1, least important).

 All dimensions are in feet, except wire diameter.

Adding more DEs does little for the gain

Adding another director is reaching a point of diminishing returns....

Exactly like a wire inverted V except you're using Delta Loop elements. As building a quad except the elements are three sided.

In my case it slopes down down like wire V yagi, and the third forms the complete wire on the bottom. Quad spacing is a good, start but optimized designs like WA5ARK did, will gives you additional gain.

Use isosceles triangle geometry for better gain.

Add reflector and directors for beam functionality and increased gain.

Use a loop length calculator to determine wire length: a full-wave loop is approximately (1005 / f) feet, where (f) is frequency in MHz

Diagram of a horizontal loop antenna suspended between trees, illustrating the use of wires, feedlines, and ropes for setup.

Delta loops are sometimes preferred over quad loops, particularly for beams, due to their simpler construction and comparable performance. The design of delta loops is inherently more straightforward, allowing for easier assembly and installation. This simplicity is particularly beneficial for amateur radio operators or hobbyists who may not have extensive experience with complex antenna systems. Additionally, delta loops can be constructed with readily available materials, making them a cost-effective option for many users. When it comes to performance, delta loops can match the efficiency and gain of quad loops, especially in certain frequency bands, making them an attractive alternative for those looking to optimize their signal transmission and reception.

One of the notable advantages of delta loops is their versatility in polarization. They can be fed for either horizontal or vertical polarization, which provides operators with flexibility depending on the specific requirements of their communication needs. This adaptability is particularly useful in varying propagation conditions and can help to ensure better signal quality and strength. Furthermore, delta loops can perform remarkably well even when installed close to the ground, which is a significant advantage in situations where space is limited or when operating from locations with restrictions on antenna height. Their low-angle radiation characteristics make them suitable for working with stations at varying distances, enhancing their effectiveness in both local and long-range communications. Overall, the combination of ease of construction, performance reliability, polarization versatility, and effective operation at lower heights makes delta loops a favored choice for many radio enthusiasts.

Diagram of a wire antenna simulation at 7.150 MHz with key measurements, including circumferences of elements and distances between components, illustrating three triangular wire configurations.

HOW TO BUILD one for yourself

• Simulate your design using NEC2 or others before building.

• Terminate legs properly to maintain traveling wave behavior, and to avoid reflections.

Select Loop Configuration

• Point-up triangle: Better for vertical polarization.

• Point-down triangle: Easier to feed from the bottom.

• Use isosceles triangle geometry for better gain and dual polarization.

• Gather Materials

  • Insulated wire (e.g., 14 AWG or stronger)

  • Balun ( 2:1 depending on impedance)

  • Coaxial feedline with CMC choke

  • Support structures (trees, masts, poles)

  • Rope or cord for tensioning and support

• Construct the Loop

  • Form the triangle using wire and supports.

  • Feed at a corner or midpoint of the base for desired polarization.

  • Use a balun or coax stub at the feed point to match impedance.

• Tune and Test

  • Use an antenna analyzer to check SWR.

  • Adjust wire lengths or feed point position for optimal performance.

SEE for dimensions WB3AYW Delta Loop Beam Using an isosceles triangle

https://forums.qrz.com/index.php?threads/40m-2ele-cubicle-quad.959475/

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