The lower the frequency of radio transmission, the more antennas are usually required. [om0et] if you want to work in the 80m to 20m band, you decide to turn to the frame antenna. You can see the project in the video below.
This antenna looks like a magnetic ring antenna. One in the video has seven rings, forming a 520mm square. Of course, the loop is an inductor. By removing some insulation, the operator can clamp a wire at different points to control the inductor. The variable capacitor resonates with the antenna, so tuning is absolutely necessary.
The physical support of the antenna is 25mm PVC. It’s not difficult to build, but is it really useful? The video shows quite a lot of construction details, but we are waiting for the second part, which will show running tests. Based on past experience, we guess it will work well, but the tuning will be fast, which means that you have to re tune many times when changing the frequency.
In addition, these antennas are often directional, so they are very useful in fox hunting. We see that many ring antennas can be hidden in the ordinary line of sight, and sometimes they can be portable.