A Growing Concern
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 [...]
Hams occasionally like to take their toys to remote locations and play radio from the top of a mountain or at a pleasant picnic in a park. This gives us a chance to set up equipment in odd places, erect antennas and generally practice for emergency communications contingencies. To encourage this practice, the ARRL (American [...]
Top Band, as 160 meters is called, presents a a challenge because the long wavelength leads to large antennas. One can always play tricks with loading to be able to use a physically shorter length of wire. There are many articles on compact 160 m antennas, but this is not one of them. Rather, I'm [...]
A lowly coil of wire can be surprisingly difficult to understand and model correctly. I use coils of wire or coils of coax cable as trap inductors for various antenna designs that I have built. In the low frequency limit, the traditional inductance calculations work okay and can give you a pretty good estimate of [...]
When you first meet the J-Pole, you are forgiven if you don't quite grok how it is supposed to work. What is that 'J' for anyhow? When I have questions like this, I get out the 4NEC2 modeling program, and see what it says. Let's start out with the basic model -- the J consisting [...]
The bamboo Moxon I built for the 20 meter band earlier this summer convinced me of the power of compact two element antennas. When I was showing the Moxon to a friend, he pointed up to a nearby tree and said "There's the place to pull from," pointing to the crotch of a tall branching [...]
Squash Practice 