With the world atwitter over a new coronavirus variant, it seems a good time for armchair epidemiologists to take a look at what is coming. Before we dive into Omicron, lets look back at the Delta surge, and before that Alpha. The figure above from the New York Times shows US new cases since the [...]
Author: Gary Rondeau
24 Hour Animated PSK Reporter Reception Reports
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 [...]
Engineering the EFHW 49:1 Transformer and Antenna
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. [...]
Performance of 49:1 Ferrite Core Transformers
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 [...]
Radio Desk for Portable Operation
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 [...]
The COVID Endgame: Elusive Herd Immunity and Relative Risk
Today all people 16 and older are eligible to get a COVID vaccination. Nationwide, about 40% of us have had at least one dose of vaccine, with >80% of those over 65 at least partially vaccinated, and more doses are coming fast and furious. It's time to contemplate how this all comes to an end. [...]
Big Wires – A 160 / 80 / 40 Meter Multi-band Antenna
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 [...]
Designing Self Resonant Coils for Antenna Traps and Chokes
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 [...]
Modeling the J-Pole
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 [...]
A 30 Meter Bamboo Pull-up Hex Beam
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 