Today is your last day to order a SotaCAT this year! Get WiFi control, click-to-tune spotting, and SotaMAT integration on your KX2/KX3. We have a few in stock still; any in-stock orders today will ship tomorrow, then we're taking the holidays off.
#hamradiohttps://store.invertedlabs.comInverted Labs, LLC by K5EM
Thanks to the operators of the VK2GGC SDR for the ability to create some of the images above by listening in on the other side of the world. The rest were heard and screenshotted on my RX-888 MKII SDR here in Seattle on a rainy afternoon. Antenna was a 40m EFHW about 20ft off the ground, and these were likely coming in from Asia or Central/South America based on the band conditions at the time.
So, back to hearing them in Palau. We can only guess that we were hearing the startup of manufacturing lines one ionospheric hop away in Indonesia or Vietnam. These are just guesses, as these signals reflect and refract off the ionosphere and could be coming from significant distances at times.
... but that clearly isn't always the case. Shielded rooms are expensive!
The timing leads to an industrial or commercial application. Sure enough, when I got home I started doing some research, and others had received these signals as well. They are likely 27MHz high frequency welding machines for vinyl and polyurethane. They should be operated in a shielded room...
My first experience with them was during the T88WA DXPedition in Palau in 2022. The sunspots were picking up so 10m was open, and we were there making contacts as the sun came up everyday. The first clue was the timing. They would start at 8AM local time, and we would tend to hear them on 10m (28MHz). At 9AM local, more would appear. The cacophony they made sounded like a Star Wars light saber battle.
Are they ionosondes, or "sounders" that measure the height of the different layers of the ionosphere? Definitely not, as sounders tend to change frequency very linearly with time.
Depending on where you are and the time of day, you may see or hear a whole lot of these or none at all. They may be super loud, right at the noise floor, or somewhere in-between. They may be there all the time or fade in and out. Some come and go in a second or two, others last 5 second or more.
Continuing discussing these funny shapes in my waterfall from the other site and cross-posting from my bsky. Sometimes when looking at HF waterfalls, we see these funny blips that change frequency quickly and make shapes that looks like tilted "S"s or some have said fishhooks. What are they? Let's figure it out!
Switched both Pavel SDR receivers to run from SparkSDR and report both FT8, FT4, and WSPR, and the results are pretty much identical to the pair of Hermes 2 Lite skimmers connected to the same antennas. The onboard decoders work very well, but only report one mode at a time currently.
I still have a couple of these extra to my needs if someone in North America wants to set up a world class skimmer for around $200. Ping me via email on QRZ if you're interested.
#hamradio #ft8 #pskreporter
