Building a Low Noise Loop Antenna for Ham Radio

Building a Low Noise Loop Antenna for Ham Radio

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Noise is a significant issue for ham radio operators, especially when working on HF bands. Many of us have experienced the frustration of trying to make contacts only to be drowned out by noise. In this blog, I’m going to share insights into a simple yet effective solution: the loop antenna. This design promises low noise and ease of construction, making it an ideal project for anyone looking to improve their setup.


Understanding Noise in Ham Radio

Noise can be a ham's worst enemy. It travels further when vertically polarized, making vertical antennas particularly susceptible. This is why many operators, including myself, have turned to alternative solutions. For instance, I’ve been in contact with Brian, ZL3XDJ, who has shared his experiences dealing with noise on 40m using vertical antennas. His insights highlight how noise can be managed, but it often requires a bit of ingenuity.

One of the common issues with vertical antennas is their tendency to pick up noise from surrounding environments. This could be from your own home, nearby power lines, or even your neighbours' electronics. The solution? A low-noise antenna design that can help mitigate these issues.


The Benefits of Loop Antennas

Loop antennas are gaining popularity among ham radio enthusiasts for several reasons:

  • Low Noise Reception: Loop antennas are inherently good at rejecting noise, making them a great choice for operators looking to improve their signal quality.
  • Easy Construction: They can be made from simple materials, making them accessible for most ham radio operators.
  • Effective Radiation Patterns: A well-designed loop antenna can provide low-angle radiation, which is beneficial for DX (long-distance) communication.

Designing Your Loop Antenna

In this section, we’ll delve into the specifics of constructing a loop antenna. The design I’m discussing is a diamond-shaped loop, which offers a unique combination of performance and simplicity. This design was shared with me by Ken (KF0NRM), who has successfully used it in his own setup.

Materials Needed

To build this antenna, you will need:

  • A length of wire (the gauge will depend on your preferences)
  • A central mast support (fiberglass masts are recommended for durability)
  • Some support cords to hold the wire in place
  • A matching unit (I recommend a 1:1 balun to balance currents)
  • Coaxial cable (50-ohm recommended)

Image: Antenna Drawing


Construction Steps

Here’s a straightforward guide to constructing your loop antenna:

  1. Determine the height of your mast. A minimum of 10 feet is recommended to avoid interference from nearby objects.
  2. Cut your wire to the appropriate length based on the frequency you plan to operate on. Ensure you have enough wire to account for the loop's shape.
  3. Attach the wire to the mast at a low point, creating two angled sections that will extend downward and outward.
  4. Use the support cords to secure the ends of the wire, creating a diamond shape.
  5. Connect your coaxial cable to the antenna feed point. It’s best to take the feeder away from the loop at a right angle for the first 5 to 10 feet.
  6. Add your matching unit at the feed point to ensure balanced currents.

Optimising Your Antenna

Once your antenna is constructed, it’s essential to optimize its performance. Here are some tips:

  • Match the Impedance: Using a balun will help ensure that your antenna is properly matched to your transmitter, reducing signal loss.
  • Test for Noise: Once erected, test the antenna for noise levels compared to other antennas. This will help you gauge its effectiveness.
  • Adjust the Height: If you experience high noise levels, try adjusting the height or orientation of the antenna to find the sweet spot.

Field Testing and Results

While I haven’t had the chance to test this antenna myself due to winter weather and recovery from surgery, the design intrigues me. Many operators report significant improvements in signal clarity and reduced noise levels when using loop antennas.

In the past, I have experimented with verticals and found them lacking due to the noise they pick up. I’m excited about the potential of this loop antenna to provide a clearer signal with less interference. If you decide to give it a try, I would love to hear about your results!


Conclusion

In conclusion, the loop antenna presents a fantastic opportunity for ham radio operators looking to combat noise and improve their reception capabilities. With a simple design and accessible materials, it’s worth considering for anyone serious about their radio hobby.

As always, I appreciate your support for this channel and my efforts to share knowledge in the ham radio community. Don’t forget to subscribe for more insights and projects! Happy operating, and I look forward to hearing your experiences with the loop antenna.

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