How to Make a 1/4 Wave Ground Plane Antenna for HAM Radio (DIY Tutorial)

Building your very own 1/4 wave ground plane antenna is easier than you think. With a few tools, a bit of 14-gauge copper wire, and LMR-400 coax cable, you can build a reliable HAM or GMRS radio antenna. It is a DIY project that boosts your signal, puts dollars in your pocket, and informs you on how antennas really work.

A 1/4 wave ground plane antenna for HAM radio is simple, inexpensive, and perfect for anyone who wants a hands-on experience working with antenna theory.

For more beginner projects, visit RadioOpBox.com Antenna Guides.

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What is a 1/4 Wave Ground Plane Antenna?

A 1/4 wave ground plane antenna is one of the most widely used and efficient local VHF or UHF antennas. It consists of:

• 1 vertical radiator
• 4 radials sloping downwards to form the ground plane.

This design produces an omnidirectional radiation pattern, which is ideal for repeater access or simplex use.

Benefits:

Easy to build and tune
Excellent local coverage
Very low cost

Drawbacks:

Bandwidth limited
Needs to be mounted properly for good performance

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Materials You’ll Need

14-gauge copper wire antenna construction example
Below is what you’ll need for your 1/4 wave ground plane antenna built using 14-gauge copper wire and LMR-400:

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• SO-239 Panel Connector – base of the antenna
• 14 AWG Solid Copper Wire – for radiator and radials
• LMR-400 Coax Cable 50ft – premium low-loss, high-quality coax
• Soldering Iron Kit – for quality joints
• Drill, screws, and mounting hardware

???? Pro Tip: Low-resistance, high-conductivity copper wire improves SWR and signal efficiency. LMR-400 coax reduces signal loss, especially on long lengths.

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Step-by-Step: Building a 1/4 Wave Ground Plane Antenna

Step 1: Calculate the Wire Lengths

Use the formula:

Length (inches) = 2808 / Frequency (MHz)
Example for 146 MHz (2-meter band):
2808 ÷ 146 = 19.2 inches

✅ Radiator: 19.2″ of 14-gauge copper wire
✅ Radials (4 total): Each 19.2″ of 14-gauge copper wire

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Step 2: Prepare the SO-239 Base

The SO-239 connector is the center hub:

Center pin: vertical radiator
Outer flange: four radials
If your connector is not pre-drilled with holes for radials, create small holes near the edges so that the wires can be tightly attached.

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Step 3: Install the Radiator

Cut away ½″ insulation and solder the vertical radiator wire to the center pin.

Straighten it out — alignment will affect antenna radiation pattern.

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Step 4: Install the Ground Radials

Securely fasten the four radials evenly spaced apart.

Fold each one down at a 45° angle to have about 50 ohms impedance for optimum radio performance.

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Step 5: Install the Antenna

Mount the antenna to a PVC pipe or mast with clamps or brackets.

Connect the PL-259 terminated LMR-400 coax cable to the SO-239 base.

For ideas on mounting, see: Building Your First HAM Base Station.

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Step 6: Tune and Test

Use an SWR meter or antenna analyzer. Adjust the radiator so your SWR is nearly 1.0:1. Trim or extend wire with caution for fine-tuning.

Read more: How to Tune and Test Your Radio Antenna

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Mount your antenna as high as possible for line-of-sight coverage.
Weatherproof solder joints with tape or sealant.
Keep radials symmetrical for optimal balance.
Recheck SWR every few months.
Using LMR-400 reduces signal loss over long coax runs.

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Recommended Tools & Accessories

• NanoVNA Antenna Analyzer – precise tuning
• 14 AWG Solid Copper Wire Roll – enough for multiple builds
• Soldering Iron Kit with Stand – safe and professional assembly
• LMR-400 Coax Cable 50ft – high-quality, low-loss.

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FAQ: Assembly of a 1/4 Wave Ground Plane Antenna

Q1: What frequency band is best for a 1/4 wave ground plane antenna?
A: Best for VHF and UHF, for example, 144–148 MHz or 440–450 MHz.

Q2: Can I use aluminum instead of copper?
A: Yes, but copper is easier to solder and gives better conductivity.

Q3: How high should I raise the antenna?
A: Best 10–20 feet off the ground for maximum line-of-sight coverage.

Q4: What coax should I use for maximum performance?
A: LMR-400 is best utilized for low-loss, long cable runs.

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Conclusion

Building a 1/4 wave ground plane antenna is a rewarding DIY HAM project. With 14-gauge copper wire and LMR-400 coax, it’s easy, cheap, and provides excellent communications performance.

Building an antenna helps you understand tuning, impedance, and signal action — skills vital to any HAM or GMRS operator.

For additional HAM and GMRS tutorials, guides, and equipment reviews, visit RadioOpBox.com.

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