A Growing Concern
Anyone who spends any time on the internet has one eye peeled for scammers. I've used eBay for many years for many online purchases and have generally had a good experience. Usually it's small stuff like like LEDs and bike parts for the DateTrike, coax connectors and cable for my radio, new or used test equipment, or [...]
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 [...]
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 [...]
Squash Practice 