Thread by @ctfallen

1st, caveat: lots can go wrong, maybe scrubbing the first ionosphere HF modification campaign with a private heater, still under construction & testing.
2nd, while this shakedown campaign, code name #SkyWeasel, has limited objectives, #radio fans may enjoy tuning in. A 🧵 1/19:

https://twitter.com/ctfallen/status/1566135586619961344

W/ max net power ~80 kw + only about ⅓ of that available for #SkyWeasel, and the ever-present possibility of enhanced D-region HF absorption in the upward solar cycle, there may not be the power to create desired artificial field aligned irregularities (FAIs). No worries! 2/19

If you have a radio that tunes 4.5MHz, or the 6 and 10m bands AND live in a swath of US southwest illustrated in maps (post later), particularly a software defined radio (SDR) that can autonomously record a narrow band around those frequencies, you may find some aether gems. 3/19

Or maybe some aether golf balls. This is operation #SkyWeasel, after all. 4/19

Some historical significance to the effort. If you capture some signal thru the noise, then you may partially recreate early experiments in the 1970s using the Platteville High Power Facility that enabled reliable 1000+ kilometer VHF comms. 5/19 Pic from doi.org/10.1029/RS009i…

How does FAI-scatter comm work? Briefly, the HF heater induces+maintains ionosphere FAIs overhead which preferentially scatter VHF/UHF in conical directions. This specular scatter is similar to what you see if you shine a laser at on a thin shiny rod or wire. Try it! 6/19

Apologies, let me go back. What are FAIs? They are variations of ionosphere plasma density aligned with the Earth’s magnetic field, like tubes. Variations in plasma density can scatter radio waves that have wavelengths comparable to the scale size of the variations. 7/19

For incompletely understood reasons, powerful HF radio waves with “O-mode” polarization can create and sustain artificial FAIs. Could this be considered dangerous or even (gasp) #geoengineering? No. The artificial FAIs dissipate moments after the HF transmissions cease. 8/19

FAIs often occur naturally for reasons also partially understood. At mid-lats they form at certain altitudes according to seasonal patterns, See the most excellent papers from the ref below, which can be used to plan opportunistic contacts. 9/19 Pic from doi.org/10.1002/2015JA…

Hams do sometimes make contacts with these natural FAIs, and FAI scatter appears to have been a popular niche mode in the late 1970s and early 1980s. Still today? 10/19 Excerpt from @ARRL’s Jan 1982 QST arrl.org/qst

The team made repeated natural FAI contact in 2020 with a 1kw VHF transmitter + Yagi antenna (~20 dbi gain) near Platteville, CO transmitting toward northeastern Nebraska / southeastern South Dakota and received in eastern Kansas. The FAIs were likely ~200 km altitude. 11/19 E.g:

An ionosphere heater can make these FAIs occur “on demand,” for an inflated price since energy isn’t cheap, enabling long-distance communication so long as the tubular specular condition (my term for it, not reputable scientists’) is satisfied. 12/19

The tubular specular condition is a demanding combination of constraints on ionosphere plasma density altitude profile, available heater frequency, and geography including the 3D structure of the Earth geomagnetic field. 13/19

For #SkyWeasel, the iono. heater and FAI scatter location is near Cheyenne, Wyoming and the 6 and 10 meter transmitter will be located near Boulder City, Nevada. This configuration closely mirrors experiments performed in the 1970s. 14/19 For example: doi.org/10.1029/RS009i…

That entire 1974 issue of Radio Science, Volume 9 Issue 11, is a 🤯 read for ionosphere modification fans, perfect for a night on the rug with a White Russian or herbal (tea). In there you will find another comm. mode w/o the FAI geometry constraint. 15/19 agupubs.onlinelibrary.wiley.com/toc/1944799x/1…

Physics behind the other mode require more power than available during #SkyWeasel so artificial FAI scatter it is, with a small fixed freq. 4.5MHz heater to boot, which means the scatter altitude and reception locations will vary thru the day, if FAIs are created at all. 16/19

But despite its limitations, the heater really ties the sky together, doesn’t it? #SkyWeasel 17/19

Tune in here over the next two-ish weeks for maps, plots and updates for participation in Operation #SkyWeasel!
(Also, for non-regulars, tune in here for nonsense, “common” sense, bad ideas, crypto foolishness, light science, complaints, sportsball, and cats.) 18/19

P.S. I didn’t exactly choose the name #SkyWeasel for this exercise but the alternative presented was ARC-X ‘22 so, “the Dude abides!” 19/19