Copasetic Flow

  Carbon-fiber masts don’t have to be the villain. For Straight Key Month I ran a quarter-wave 20-meter vertical two ways—first with 12-gauge wire taped to the outside of a Goture carbon-fiber mast, then with 18-gauge magnet wire laced inside the mast. Result: both versions delivered S9 into Utah from downtown San Francisco, and the internal-wire build was far stealthier for city operating. I finally got to do a long term—a few hours—test of the TouCans and a Stick vertical antenna with magnet wire on the inside this week! The interior magnet wire setup worked just as well as the same antenna rigged with 12 gauge wire taped to the outside of the carbon fiber mast did. The rig was S9 into the Utah SDR that morning. Here's a look at the antenna setup and results. There are more text details below the video.. Construction To construct the antenna I removed the brass bottom of the carbon mast, removed the upermost segment, and then inserted 18 guague magnet wire through the...

 An AM broadcast station was loud in my headphones for about two minutes. Then, TouCans mysterious noise cacnellation circuit charged, and the POTA was off and running. According to the POTA website, I haven't activated US-0757 , aka the San Francisco Maritime National Historical Park , in about eight months. It was nice to be back! We'd had about a week's worth of atomspheric river rains, so it was pretty phenomenal to have this view during the activation. The temperature was in the low 60s which was very pleasant. I didn't go for a swim this time, but I'm going to get back to that soon as well. View of the Golden Gate Bridge from over my shoulder The transit ride—SF MUNI 54 to BART to San Francisco MUNI 30—was a piece of cake as always. The video below shows part of the route as seen from the bus window. I just now realized that I copied my opeining into the video twice. You didn't imagine it. Sorry about that :) I stopped for lunch at the Buena Vista I...

 Project TouCans and kitchen window antenna are continuing to work well during straight key month! This is just a quick update. The rig layout can be seen in the video below.

 I made eight QSOs on my first hour long straight key month shift operating as K3Y/6! Points of note: I'm still operating five watts from the kitchen window in San Francisco. The ' shiny F2 ' cutoff was not disproven. The critical frequency between San Francisco and Utah did go below 7,750 kHz and there was only one QSO that went east of Louisiana out to New York. That happened when the fof2 value was about 8200 kHz. Does the Data Fit with ND7K in Arizona? I noticed that while Utah had disappeared again, I was still being spotted in Arizona at 01:00 UTC. Looking at the fof2 values to the spotting station, ND7K revealed that this spot conformed to my evolving rule of thumb. The midpoint fof2 is at about 8,000 kHz at the time, so above 7,750 kHz. Note for future use: The rig's freuqncy/fof2 = 14.0574/7.750 = 1.8138 The factor is for use with this figure.

 A few afternoons ago, I watched the signal from TouCans fade from an s9 into the Utah SDR to nothing in a matter of minutes. There was nothing wrong with the rig. I was literally getting to observe the effect the F2 layer has on propagation on twenty meters. Schedule 00:02 UTC/16:02 PST: Almost at S9 into Utah 00:32 UTC/16:32 PST: Running at S9 into Utah 00:36 UTC/16:36 PST: Already down to S5 00:37 UTC/16:37 PST: The signal is all but gone What Happened? Here's the F2 critical frequency, (fof2), along the path to Utah at each of the above time steps.  The critical frequency is the maximum frequency that will be reflected straight back down to the ground at any point rather than piercing the ionosphere and propagating out into space. When I say along the path, I mean the value for fof2 reported by GloTEC  at that time. GloTEC collects a number of ionospheric data sources and assembles them into a model of what the F2 layer looks like at any location on Earth at a give...

  FM modulation is so elegant it almost feels like a magic trick. After finally watching a 1940s U.S. Army Signal Corps training film, I realized just how simple frequency modulation really is—both on transmit and receive. Seeing the LC tank, limiter, and discriminator explained visually made everything click. Even better, that understanding immediately paid off in a modern, practical way: fixing an overly aggressive CW sidetone in my video QSLs using nothing more than an audio limiter. I finally understand FM modulation and it's so simple I'm amazed it wasn't developed first. I found an old US Army signal corp video that describes how both FM transmit and receive work. Audio Modulation I had not understood that modulating the transmit frequency was this simple. It all makes sense now that I see it, but I hadn't considered how simple this could be. The video demonstrates the use of an LC tank circuit to  generate the required RF. By placing a a condenser mic in p...