PowAbeam Antennas - Research

Qwen Yagi-Uda QWEN8144 design...

PowAbeam Antennas - Research... 8th November 2026

Page derived from QWEN8144 Yagi-Uda design (Qwen text file output)

Designing an 8-element Yagi-Uda antenna for 144.5 MHz with a **wide bandwidth** requires a specific architectural approach. Traditional Yagi designs often sacrifice bandwidth for gain, but two proven design methodologies excel at providing both: the **OWA (Optimized Wideband Array)** and the **DL6WU long-boom** style.

Since 144.5 MHz sits right in the middle of the 2-meter band (144–148 MHz), a design optimized for the entire band will perform flawlessly at your target frequency. Below are two complete, computer-optimized designs you can build.

### Option 1: 8-Element OWA Yagi (Highly Recommended)
The Optimized Wideband Array (OWA) was pioneered to provide exceptional bandwidth and a direct 50-Ohm feedpoint impedance without the need for complex matching networks (like gamma or hairpin matches). [[34]] This design uses a shorter boom, making it mechanically simpler and lighter while maintaining excellent wideband performance. [[34]]

**Specifications:**
* **Target Frequency:** 144–148 MHz (Peak performance centered around 145 MHz, excellent at 144.5 MHz)
* **Element Material:** 3/16" (4.76 mm) diameter aluminum rod parasitic and 5/8" (15.875 mm) tube driven
* **Boom Length:** 115.0 inches (2.92 meters)
* **Expected Gain:** ~12.4 dBi
* **SWR:** 1.2:1 across the entire 2-meter band [[34]]

**Dimensions (from Reflector):**

| Element | Length (inches) | Length (mm) | Position from Reflector (inches) | Position from Reflector (mm) |
| :--- | :---: | :---: | :---: | :---: |
| **Reflector** | 40.70" | 1034 mm | 0.00" | 0 mm |
| **Driven Element** | 38.95" | 989 mm | 11.18" | 284 mm |
| **Director 1** | 37.00" | 940 mm | 15.47" | 393 mm |
| **Director 2** | 36.32" | 923 mm | 27.38" | 695 mm |
| **Director 3** | 36.32" | 923 mm | 42.72" | 1085 mm |
| **Director 4** | 36.20" | 919 mm | 63.38" | 1610 mm |
| **Director 5** | 35.20" | 894 mm | 88.50" | 2248 mm |
| **Director 6** | 33.30" | 846 mm | 115.00" | 2921 mm |

*Note: The driven element is split in the exact center for a direct coaxial feed.*

### Option 2: 8-Element SM5BSZ / DL6WU-Style Optimized Yagi
If you have the space for a longer boom, this design is mathematically optimized specifically for 144.5 MHz using the brute-force optimization method. [[3]] It offers a very clean radiation pattern and wide bandwidth, but requires more precise construction. [[3]]

**Specifications:**
* **Target Frequency:** 144.5 MHz
* **Element Material:** 5.2 mm diameter aluminum rod
* **Boom Length:** 4.346 meters (171.1 inches / ~14.25 feet)
* **Expected Gain:** ~12.42 dBd
* **SWR:** Optimized for a direct 50-Ohm match (reZ=50 Ohms, imZ=0 Ohms) [[3]]

**Dimensions (from Reflector):**

| Element | Length (mm) | Length (inches) | Position from Reflector (mm) | Position from Reflector (inches) |
| :--- | :---: | :---: | :---: | :---: |
| **Reflector** | 1019 mm | 40.12" | 0 mm | 0.00" |
| **Driven Element** | 922 mm | 36.30" | 364 mm | 14.33" |
| **Director 1** | 953 mm | 37.52" | 487 mm | 19.17" |
| **Director 2** | 942 mm | 37.09" | 1011 mm | 39.80" |
| **Director 3** | 921 mm | 36.26" | 1802 mm | 70.94" |
| **Director 4** | 910 mm | 35.83" | 2658 mm | 104.65" |
| **Director 5** | 906 mm | 35.67" | 3528 mm | 138.90" |
| **Director 6** | 920 mm | 36.22" | 4346 mm | 171.10" |

### Critical Construction Tips for Wide Bandwidth

1. **Stick to the Element Diameters:** The designs above are tuned for specific element thicknesses. Changes in the element lengths are required for changes in the element diameters. [[34]] If you must use thicker tubing (e.g., 1/2" or 12mm), the elements will need to be shortened, and the spacing will require re-optimization.

2. **Boom Material Matters:** The dimensions assume the elements are electrically isolated from the boom. If you use a metal boom, you must insulate the elements from it (e.g., using plastic or fiberglass sleeves), as metal booms detune the antenna. [[34]] Alternatively, use a non-conductive boom like fiberglass, PVC, or wood.

3. **Feed System:** Even though the OWA design provides a native 50-Ohm match, you should **always** use a 1:1 current balun (choke) at the feedpoint. This prevents common-mode currents from traveling down the outside of your coaxial cable, which can severely degrade the SWR and distort the radiation pattern.

4. **Tolerance:** For wideband performance, the relationship between the driven element and the first director is critical. Keep your measurements as precise as possible (within ±1 mm or 1/16"), especially for the first three elements.

*If you plan to build this, the **Option 1 (OWA)** design is generally the most forgiving for homebuilders while still delivering professional-grade wideband performance on the 2-meter band.*

Terms and conditions

These yagi antenna designs aren't for commercial use of any kind without prior consent!

Private experimenters are free to use these designs for their own personal enlightenment. However, no guarantee or warranty is offered or implied.

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