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.

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### 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.*

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### 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" |

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### 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.*