When I was a kid, my crystal set had permeability tuning (ferrite slug within a coil) and it worked very well right across the AM band. One of the best indoor antenna connections was the metal dial on the Bakelite telephone.
I fondly remember my first crystal set. Well before I had learnt to read a circuit diagram and was building anything. Dad came home with two crystal sets. For me and my older brother. About the size of a cigarette pack. Predominantly white with a red length of wire and alligator clip for the antenna. The typical crystal earpiece you see. On the front was a dial for tuning, and it all worked very well. Some time later when I opened it, there a coil with multiple turns over top of each other. A ferrite rod slid in and out controlled by a wired mechanism as you turned the dial. It had a fixed capacitor across the coil and a germanium diode.
Although the "point-contact" germanium diode was originally developed as a detector, you will get better results if you can obtain a later "gold-bonded" type developed for early computer applications, e.g. OA47, AAZ18, CG84 etc.
I use an old telephone handset for audio out. There are a couple of strong MW AM stations locally. Using approx 40m wire and good ground, the audio level is very good, such that I've added a variable resistor in series with the handset to lower the volume for comfortable listening.
It shows our age doesn't it? How many kids today are enthusiastic about crystal radio! And the hammer is very useful indeed for chipping the crystal out of the granite.
Thanks Peter for putting these kind of videos up on UA-cam, I really enjoy them! I am in Southern Ontario, Canada and have experimented with crystal sets in the past with fair to excellent results. I am lucky to be in Southern Ontario the Niagra wine belt and the greater Totonto areas. Like the USA, we have 10 kc spacing and the Medium Wave band is still very popular with lots of stations to tune to. At night there are many more strong signals through propagation. The biggest problem is selectivity.
I built a crystal radio in a Radio Shack 100 electronic projects kit I got for Christmas when I was stateside in the US. When we returned to the Bahamas I remembered the schematic from memory and had my mom pick up the 1N34a germanium diode, AM ferrite loopstick coil, 365 pF ( then mmf) a 10,000 ohm resistor, fahnestock clips and a crystal earphone. I mounted all the parts on a short piece of pine board. I got it working on shortwave first ironically because I tapped the center tap on the coil. I picked up AM stations from Miami, Florida when I used the entire length of the coil.
I was watching a video yesterday and the diode got a special mention. It seems there are some not so kosher germanium diodes from china. My favourite is the " Mystery Crystal set " first published Brisbane 1932. A beautiful performer i recommend.
Great video. For one of the "bad" circuits you mention that it can be improved by placing a small cap in series with the aerial. I tried this and it seems to help. What is it doing exactly?
The small cap may introduce a bit of loss but it lessens the extent to which the antenna loads the tuned circuit, reducing its Q and making it less selective.
Man I wish teachers would stop with the high impedence phone talk. Just stop. The choice is spending a bundle on ancient deteriorated, or new poorly made. Just stop. Please, please eliminate all discussion on them and do the right thing. Talk about audio amps.
When I was a kid, my crystal set had permeability tuning (ferrite slug within a coil) and it worked very well right across the AM band. One of the best indoor antenna connections was the metal dial on the Bakelite telephone.
I fondly remember my first crystal set. Well before I had learnt to read a circuit diagram and was building anything. Dad came home with two crystal sets. For me and my older brother. About the size of a cigarette pack. Predominantly white with a red length of wire and alligator clip for the antenna. The typical crystal earpiece you see. On the front was a dial for tuning, and it all worked very well. Some time later when I opened it, there a coil with multiple turns over top of each other. A ferrite rod slid in and out controlled by a wired mechanism as you turned the dial. It had a fixed capacitor across the coil and a germanium diode.
I see so many stories like this, I wish they were still around. You know if the one you had is still around?
Still a lot of fun to be had from a crystal set, thanks for the tips Peter. 👍
Although the "point-contact" germanium diode was originally developed as a detector, you will get better results if you can obtain a later "gold-bonded" type developed for early computer applications, e.g. OA47, AAZ18, CG84 etc.
ARE THOSE PARTS SOLDERED ON THE MOTHER BOARD
wish I had UA-cam and your channel 60 odd years ago Peter - excellent advice...
I use an old telephone handset for audio out. There are a couple of strong MW AM stations locally. Using approx 40m wire and good ground, the audio level is very good, such that I've added a variable resistor in series with the handset to lower the volume for comfortable listening.
Just about the most comprehensive account of crystal radios I’ve ever come across - fantastic.
It shows our age doesn't it? How many kids today are enthusiastic about crystal radio! And the hammer is very useful indeed for chipping the crystal out of the granite.
This is an excellent post with tons of useful ideas!
I agree. If it weren't for Peter and a few other youtubers I would have thought that the crystal radio hobby was a thing of the past.
1.b.
In Hungary, there is only daytime radio broadcasting on medium wave.
Solt between 0430 .. 2230, Miskolc 0500 .. 2105 local time.
Thanks Peter for putting these kind of videos up on UA-cam, I really enjoy them! I am in Southern Ontario, Canada and have experimented with crystal sets in the past with fair to excellent results. I am lucky to be in Southern Ontario the Niagra wine belt and the greater Totonto areas. Like the USA, we have 10 kc spacing and the Medium Wave band is still very popular with lots of stations to tune to. At night there are many more strong signals through propagation. The biggest problem is selectivity.
I built a crystal radio in a Radio Shack 100 electronic projects kit I got for Christmas when I was stateside in the US. When we returned to the Bahamas I remembered the schematic from memory and had my mom pick up the 1N34a germanium diode, AM ferrite loopstick coil, 365 pF ( then mmf) a 10,000 ohm resistor, fahnestock clips and a crystal earphone. I mounted all the parts on a short piece of pine board. I got it working on shortwave first ironically because I tapped the center tap on the coil. I picked up AM stations from Miami, Florida when I used the entire length of the coil.
I was watching a video yesterday and the diode got a special mention. It seems there are some not so kosher germanium diodes from china.
My favourite is the " Mystery Crystal set " first published Brisbane 1932. A beautiful performer i recommend.
Interesting points, thanks.
Great to work you during lighthouse weekend as ZL2KS, Stuart ZL2TW
nice book collection
Great information thank you
Great video, thanks! I subscribed!
Great video. For one of the "bad" circuits you mention that it can be improved by placing a small cap in series with the aerial. I tried this and it seems to help. What is it doing exactly?
The small cap may introduce a bit of loss but it lessens the extent to which the antenna loads the tuned circuit, reducing its Q and making it less selective.
As a kid in Brooklyn Crystal radios worked with Barely any antenna
Man I wish teachers would stop with the high impedence phone talk. Just stop.
The choice is spending a bundle on ancient deteriorated, or new poorly made. Just stop.
Please, please eliminate all discussion on them and do the right thing.
Talk about audio amps.
THANK YOU. Good information