Exploring the Versatility of Tape Measure Antennas for Portable Ham Radio

Exploring the Versatility of Tape Measure Antennas for Portable Ham Radio

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Exploring the Versatility of Tape Measure Antennas for Portable Ham Radio

For those who enjoy portable ham radio operations, having a reliable and efficient antenna is crucial. Recently, an innovative idea came to my attention that involves using tape measures as radials for vertical antennas. This concept not only provides portability but also offers flexibility in adjusting the length of the radials without the hassle of cutting wires. Let’s dive into the details of how this idea works and its benefits.

Understanding the Concept of Tape Measure Radials

Tape measures are familiar tools, but their application in ham radio is less common. The idea of using tape measures as radials stems from their adjustable length, allowing operators to optimize their performance without permanent modifications. This adaptability can be particularly beneficial when setting up portable stations in varying environments.

One of the primary advantages of using tape measures is that they can be easily folded, making them incredibly portable. When not in use, they can be stored compactly, fitting into backpacks or even pockets. The increased cross-section of a tape measure compared to a standard wire also enhances the ground coupling, which can improve performance, especially when the antenna is mounted close to the ground.

Setting Up the Tape Measure Antenna

To implement this idea, I decided to use a versatile antenna, the AO A25, which is designed to be easily assembled and adjusted. This antenna features a base loaded design that fits well on a camera tripod, making it perfect for portable use.

Here’s a quick overview of how to set up the antenna with tape measure radials:

  1. Start with your tape measure, ensuring it’s in good condition and can extend fully.
  2. Connect the tape measure to the base of the antenna using a crocodile clip. This can be done by either soldering a short wire to the tape or drilling a hole to secure the clip more firmly.
  3. Adjust the height of the tripod to ensure the antenna is elevated above the ground, which can help reduce losses.
  4. Extend the tape measure radials as needed to find the optimal length for your setup.

Initial Testing and Performance

During my initial tests, I noticed that the length of the tape measure radials was significantly shorter than expected. For 20 meters, the optimal length was around 2 meters, which is less than half the traditional quarter-wave measurement. This adjustment led to a surprising VSWR (Voltage Standing Wave Ratio) of approximately 1.1:1, indicating a good match.

The compact nature of the setup allowed for quick deployment, and I found that the performance was encouraging. While operating with 5 watts on 20 meters, I was able to make contacts at distances of 500 to 1,000 kilometers, which is impressive for portable operations.

Ground vs. Elevated Radials

One interesting aspect of my testing was comparing the performance of elevated radials versus those mounted on the ground. Elevated antennas typically reduce earth losses, leading to improved efficiency. However, when I tested the tape measure on the ground, I found that the shorter radial length still produced a good match.

This observation raised questions about the traditional understanding of radial lengths. It appears that when the radials are used on the ground, they can be much shorter than the expected quarter-wave length. The effective coupling with the ground and the adjusted feed point may contribute to this phenomenon.

Using the Antenna on Different Platforms

Another benefit of the tape measure radial setup is its adaptability to various platforms. For instance, I experimented with mounting the antenna on the roof of my fiberglass motorhome. By extending the tape measure along the roof and connecting it to the antenna, I achieved a good match and made several contacts.

This setup is not limited to motorhomes; it also works well on standard vehicles. The ability to quickly adjust the radial length makes it a versatile choice for different operating environments.

Final Thoughts and Recommendations

Using tape measures as radials for portable antennas offers a unique blend of portability and performance. The convenience of adjusting radial lengths without cutting wires is a significant advantage for portable operators. While the tape measure itself may not drastically improve performance, the overall setup is efficient and easy to manage.

If you’re looking for a portable antenna solution that is both practical and effective, consider experimenting with tape measure radials. This approach not only simplifies the setup process but also opens up possibilities for using your antenna in various settings.

Thank you for joining me on this exploration of tape measure antennas. If you have any experiences or tips related to portable antennas, feel free to share your thoughts!