The Electrical Experimenter (1913)
library.si.edu
library.si.edu
It's got some great projects for anyone who's looking to get into radio. Check out page 100 for an example of one of those crazy projects. It looks like it's a 50-foot areal hooked up to a 4-tap isolation transformer being AC coupled to headphones. It's using a basic single diode detection circut (you can check EEVBLog's latest video to see them being used in the spy bug detector). Nifty stuff and remindes me of fox hole sets
Google the quote "Marconi is a good fellow. Let him continue. He is using seventeen of my patents." for more back story.
I might recommend to search out the early chemistry books, as well. They explain the early chemistry and processes of so many things we take for granted, in a lost art kind of way. I love reading these kind of books.
Volume 1: https://archive.org/details/chemistrytheoret01muspuoft
Volume 2: https://archive.org/details/ldpd_10922488_002
Most of the theory is nonsense by modern standards. But it's amazing to see how sophisticated the chemical process industries were already in the mid 19th century. And it's self contained: the manufacturing processes start from plant matter, things you can dig out of the earth, or other materials whose manufacture is described in the same book. The difference between this and a modern chemistry or chemical engineering textbook is, for a rough analogy, the difference between exploring how computers work on an Apple II vs. on a powerful modern laptop with all the Debian packages installed. The modern environment is broader and more powerful, but the older one has the benefit of making all the pieces visible at once and down to a low level. (Well, it's a benefit for the curious anyway. I won't claim that experience with old 8 bit computers makes for measurably better developers, or that reading dusty historical tomes makes for more capable chemists or ChemEs.)
Another thing that I enjoy about old chemistry books is the engagement of all the senses. Chemists observed and wrote about color, crystal texture, scent, the sounds procedures made, and even taste. Bad for life expectancy, great for reading. NMR spectra, though far less ambiguous and far safer for identifying substances, just aren't as much fun to read. The procedures that are described may be horrendously unsafe but they also reliably include enough details to reproduce. I hate the abbreviated style that you see in some modern articles where the authors are thrifty with detail in the experimental section. These old works were written to inform other people of useful and/or striking observations about nature, not to grind for XP on the track to tenure, and it shows.
Here's a direct link to the PDF if you prefer that over the JavaScript reader [97 MB] https://archive.org/download/electricalexperi04gern/electric...
On a side note: oh, how times have changed: (pg 942)
Horse Sense
If you work for a man, in
heaven's name work for him.
If he pays wages that supply you your
bread and butter, work for him,
speak well of him, think well of
him, stand by him, and stand by the
institution he represents. I think
if I worked for a man, I would
work for him. I would not work
for him a part of his time, but all
of his time. I would give an un-
divided service or .none. If put to
a pinch, an ounce of loyalty is
worth a pound of cleverness. If
you vilify, condemn and eternally
disparage, why, resign your posi-
tion, and when you are outside,
damn to your heart's content. But,
I pray you. so long as you are a =
part of an institution, do not con-
demn it. Not that you will injure —
the institution — not that — but when
you disparage the concern of which
you are a part, you disparage your-
self. — Elbert Hubbard.From my understanding, a coherer was a radio-wave detector that used ferrite particles (in a small sealed glass tube, with wire at each end) that - when the radio signal was strong enough - would "stick together" and form a circuit; you can think of it as an RF-activated "reed switch" or relay. It was very crude, and not easily tunable.
Also - another interesting tidbit of info about early wireless: In order to generated the higher carrier-wave frequencies, they used special multi-pole alternators spun at high speed. Rather than only having a few poles, like a regular power generator, these RF alternators would use sometimes hundreds of poles. The RPM, multiplied by the number of poles, would determine the frequency of the output signal carrier wave. This was mainly used for telegraphy; I'm not sure if these machines had the bandwidth for voice. At the same time, they still produced a ton of power like a standard alternator - so it was essentially a way to generate "high power" (100s to 1000s of watts) RF (in the KHz ranges).
Another early technology of the time (used for a variety things - including motor control) was something called "magnetic amplifiers"; they are essentially weird variations on standard AC transformer technology. They can be made to act as audio amplifiers, as well as switches (like a vacuum tube or transistor).
Killing Sharks by Electricity