NavList:

Frank asked, "Just to clarify, did you make this recording with that receiver?"

That recording was captured with my phone from the speaker of a Hallicrafters S-38B (vintage "all American 5" vacuum tube receiver with  .55 to 30 MHz coverage). I got out the DIY regen Rx afterward just for "kicks". I did tune the regen to CHU and had pretty good reception early in the morning, sounding almost as good as the Hallicrafters. I can still pick up CHU just now (just after noon 2/24/24), but the noise floor is much higher in the daytime and 80 meter propagation is not so good. I've attached 2 recordings from the regen Rx. One is the noisy daytime CHU  signal (not so impressive) just now, the other is a 100KW station out of Tennessee taken early yesterday morning. For full disclosure, the regen Rx is 1 transistor and will drive high impedance headphones. I have it connected through a solid state amplifier in the picture and as recorded. I believe the amp uses an LM386 chip.

By the way, the Wiki article on CHU mentions that it went into service originally to provide a time reference to surveyors working in Western Canada, so that longitude could be determined.

Regarding the "apocalypse" recovery, I expect vintage vacuum tube receivers and transmitters will fare ok, if you can find the current to heat the filaments : ) The cell towers... maybe not so much. I've made diode detectors for AM demodulation from PbS (galena), Iron Pyrite, hot-rolled steel vs pencil lead, razor blades (see old Boy Scout manuals). Zinc Oxide turns out to be an interesting material for its non-linear conductance behavior (negative differential resistance) allowing oscillatory function (transmit).

https://sparkbangbuzz.com/zinc-40-meter-xmtr/zinc-40-meter-xmtr.htm

Is radio assisted navigation (other than GPS) suitably on-topic for NavList? There are still a few NDB's around and I find early developments (1910'-1940s) interesting.

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