What in Heaven's name is a "CFHW"? A CFHW is a Center-Fed Half-Wave antenna. You may know it better as a dipole and it is indeed a highly efficient simple wire antenna. I can't claim originality for the term "CFHW"; it started as a joke on one of the forums I follow. Following the trend … Continue reading The CFHW – a simple, efficient HF antenna I may never use
Category: Builder Projects
A highly efficient multiband QRP L-match builder project
Here is a project that provides a much more efficient way of matching an End-Fed Half Wave antenna than the usual 49:1 impedance transformer. High ratio transformers are prone to inductance leakage, core saturation and overheating leading to low efficiency. Although a 49:1 (or similar high ratio) transformer can present a low SWR to a … Continue reading A highly efficient multiband QRP L-match builder project
Engineering challenges of the completed QRP EFHW coupler
Kudos to Kits and Parts, the United States Postal Service and the Canada Post dog sled teams who fearlessly fought their way through blizzards on the frozen barren tundra into the wild white yonder to safely deliver my package of toroid cores. But, as soon as I had unpacked the goodies I realized I may … Continue reading Engineering challenges of the completed QRP EFHW coupler
A 20-minute QRP End-Fed Half-Wave antenna coupler
It was almost time to make lunch but I had an idea that just wouldn't wait. I figured I had 20 minutes to zip down to the basement shack/development lab and throw a simple circuit together on the workbench. I had been re-reading (for the 1000th time) AA5TB's website about using a parallel tuned circuit … Continue reading A 20-minute QRP End-Fed Half-Wave antenna coupler
KD5ZZU’s very elegant build of “Old Barebones” – a Z-match tuner
Back in October 2024 I wrote a post with the title “Old Barebones” – A QRP Z-match Builder Project. The project's purpose was to construct a simplified version of the Norcal Z-match tuner (which I also owned) to use with my QRP Labs QMX transceiver. The Norcal tuner included some features that I simply did not … Continue reading KD5ZZU’s very elegant build of “Old Barebones” – a Z-match tuner
The ultimate rebuild of an ancient Yaesu FT-817.
I think it was a couple of years ago now I ordered a QRP Labs QMX transceiver. It quickly, but temporarily, became my favorite radio for portable field operations. I have written before about why I believe the QMX is a mighty fine piece of miniaturized technology but is less suitable for the rigors of … Continue reading The ultimate rebuild of an ancient Yaesu FT-817.
Great ideas from Ham Radio Outside the Box subscribers
QRV: An interesting iOS/Mac app for hams from Adam K2CAT who writes: I developed QRV to be the ham app that I always wanted. There are a lot of great tools for amateur operators: QRZ, HamQSL solar conditions, PSKReporter, and more; they just were scattered and some are not mobile friendly. My goal was to … Continue reading Great ideas from Ham Radio Outside the Box subscribers
What really determines the efficiency of an antenna?
Is it Standing Wave Ratio (SWR)? It is common knowledge that when an antenna has high SWR some of our transmitted power is wasted instead of being transmitted. But is this really true? The trouble with "common knowledge" is that it spreads without further scrutiny. "It must be true because that's what everybody thinks". But … Continue reading What really determines the efficiency of an antenna?
4:1 Balun or 4:1 Unun – how to choose?
Perhaps one of the greatest confusions in the hobby of ham radio is wrapped around the subject of baluns and ununs. What are they, where should they be used and what do they do? At Ham Radio Outside the Box several antennas that need a 4:1 impedance matching device have been described. Since I had … Continue reading 4:1 Balun or 4:1 Unun – how to choose?
QRP? Are we out of our minds?
If we believe in QRP - I mean really, really believe - then we can make it work. Admittedly it's like betting on a race between a tortoise and a hare; where would you put your money? If you read accounts written by diehard QRPers, do you ever see stories such as: "I went to … Continue reading QRP? Are we out of our minds?
Ham Radio Outside the Box 