A Growing Concern
Mono-band vertical antenna arrays can obtain impressive directionality when built properly. These "four square" designs usually use four ground plane vertical antennas spaced 1/4 wavelength apart in a square array and fed with a carefully built phasing system. What I'm going to describe is a much simpler pull-up or mast-supported wire vertical array that gets [...]
Hams have commonly used tall trees to support their wire antennas. In the Pacific Northwest we grow very tall trees. On my one acre lot there are over a dozen of the giants. In keeping with the ham spirit of cobbling together something that works from what you have on hand, I've had great success [...]
In this article I discuss getting the three element hex beam to work well. Please see Designing a Three-Element Hex Beam and Building the Three-Element Hex Beam for those phases of this project. The hex beam is basically a compact Yagi. Like the Yagi, the parasitic elements of the hex beam develop RF currents that [...]
I describe here a simple RF current probe that can be used to directly measure RF currents in wires and cables using an oscilloscope. The probe features "clip-on" operation, using a common clip-on RFI suppression ferrite core for the sensor coil. This was "take two" for coming up with a suitable current sensor for measuring [...]
Over the winter I started work on constructing the three-element hex beam that I designed previously. This is "take two" on the basic hex beam idea, having first built a large 30m bamboo pull-up hex beam a few years ago. I've had time to figure out what I like and don't like about that first [...]
When it comes to understanding the performance of HF antenna systems, there are only a few tools. You can measure the impedance match with an antenna analyzer, you can model the antenna to see what you might expect the antenna to do, and you can listen and talk on the air to see how well [...]
My bamboo pull-up hex beam has been a work horse antenna for the last couple of years. It underwent a few changes from the initial design. I removed the 30 meter wires because the antenna was just too large to turn easily and get up and down between the branches with the space needed for [...]
PSK Reporter is really a very cool program that collects reception reports from a myriad of users and displays the results, filtered in just about anyway you can imagine, on a map on your computer screen. I use it all the time to help me understand which parts for the world are open to communicating [...]
After doing the ferrite transformer scaling experiments last time, and learning a bit more about what matters in these transformers, it was time to make a stab at designing one. Let me review the salient observations from the previous work. 1) More primary turns and primary inductance improve the transformer efficiency and low end performance. [...]
There are quite a few recipes for building a suitable transformer for an end fed half wave antenna (EFHW), but I was never sure I really understood the main principles. So, I wound a bunch of transformers, made measurements on them using my NanoVNA, learned how to get what I really wanted out of the [...]
Squash Practice 