This all reminds me of the first two build-it-yourself radio kits I got as a child. In each case it required a good antenna for a decent signal from a nearby station, and a good connection to Ground to ensure a complete circuit from antenna to Ground. The first was a true old Crystal Radio kit with a variable inductor and some small capacitance simply from the spacing of circuit components comprising the tuner circuit (to select the frequency). It had a small metal spring and a crystal of quartz (I think) to function as the diode "detector". You had to fiddle with how the spring tip touched the crystal surface to get a poor connection that acted as a diode that allows current to pass in only one direction. That current was fed to a simple earphone for sound. All of the electrical power for that sound was from the signal picked up by the antenna, so it had to be a strong signal.
The second came a bit later in a different kit. It had a variable inductor again, but the signal selected was fed to a single-transistor amplifier powered by an AA battery. The transistor acted as diode detector and amplifier that fed an earphone, again. So it could receive marginally weaker signals than a simple crystal radio, but they still had to be pretty strong. As a child I used these to listen secretly (via the earphone) to evening radio programs after being put to bed.
I am reminded also of a unique radio design I read about but never built. It had TWO tuners for different functions. The first was a simple standard AM radio with a single-stage amplifier, like one above. The other tuner was to get free electrical power "out of the air". You tuned that to a very strong local AM station and the circuit merely rectified the signal to half-wave DC that charged a large capacitor, and that was the power source for the actual radio's amplifier.
Old MAD magazine joke, I believe. What happens when a HiFi enthusiast overloads the equipment to get HUGE sound? Ampli-Fire.
Crystal detectors, AKA cat whisker crystal detectors.
From the same friend, i got a cat whisker detector about 20 years ago.
Also known as a crystal detector. And a small piece of mineral. It is either galena or Pyrite. I have to have a closer look to see what it is.
I mention pyrite in the schematics below but i was not sure at the time and had to make a choice between galena or pyrite.
To show that it is a real diode. I made a small setup. I posted it once on a similar (famous) gathering but there i was hated and being called a "Wise-Ass".
I had to look up the definition and i certainly am nothing like that : Presenting myself as a very annoying know it all. 😢
Soon i found out that these people were nothing more than jealous and lazy and they love to make others work for them.
And when you have passion for something, a hobby interested or something other, and you enjoy it and love to share the love and passion for nature and electronics...
These unfortunate simple minded people will do everything in there power to take away the joy you feel. Mostly because i would not either build or repair what they desired...
Or explain everything on demand.
What too much booze and perhaps drugs can lead too. It is sad... 😢
Their favorite way is to prevent people like me from a good night of sleep, night after night for months. Waking people like me up, while those people like me are in their deepest sleep. Which made my sickness worse... 😢
Studying hard as a young lad to have a good life later in life. Only to be gazed upon with jealousy.
Of course, working with the mind while in the office or allowed to work at home because of being ill but still able to work. 😢
That is not working in the eyes of the jealous.
Anyway, back to subject :
It is fun to see how many materials exhibit semiconductor behavior and diode behavior.
There is quite a list here i just found out :
Details of the cat's whisker radio detector or crystal detector - how this detector worked, the different types and the history of its development.
www.electronics-notes.com
And some years ago i made a setup to show the diode behavior of a cat whisker detector.
The image is with Dutch words. But the symbols are easy to understand.
One can see the forward conducting current (black multimeter) and forward conducting voltage (red multimeter).
One can see the reversed biased diode in effect. The non conducting voltage(red multimeter) and leakage current (black multimeter).
As we see in this graph :
You know what would be great fun ?
Let us say we have all decided to pretend we need to survive for a fun survival week and have to build rudimentary transmitters and receivers.
Keep it with rudimentary receivers first as that is easier. To receive assignments.
A fun thing to know, is that it is even possible to use a flame as a lousy diode. It works, not perfect but nevertheless, interesting .
Maybe anybody reading this can test this out, if an AM radio will work with a flame based diode detector ?
One would have to use two (the same) metal wires with a match or perhaps it needs to be a tube gas flows from that is burning.
Of course, one can experiment with different metals in the flame to improve the diode behavior.
Disclaimer :
I took the diode characteristic from this site, it was easier than to draw one of my own.
For those interested, there is a section about diodes on this site :
Introductio to Semiconductor Diodes, silicon diode construction. How diodes work and diode characteristics
learnabout-electronics.org