Building a Simple Radio Using Tank Circuits and Diodes - DC To Daylight
ฝัง
- เผยแพร่เมื่อ 30 พ.ค. 2024
- In this theory-based video, we combine our knowledge of tank circuits and diodes to create the simplest of radios - the crystal receiver! We'll look at the V-I characteristics of germanium and silicon, as well as the lead-sulphide crystal Galena.
Derek also shows how to design an air core inductor to work in concert with a variable capacitor, which will act as a tuning device for our radio. Our diode will act as a detector, which recovers the audio signal and removes the RF component. This is a great beginner project, a lot of fun to put together, and a good opportunity to show off your build skills!
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#0:00 Welcome to DC to Daylight
#0:54 1924 Radio
#2:54 Schematic
#4:55 Curve Tracer
#6:17 Building It!
#6:55 Air Core Inductor
#10:33 Radio
#13:27 Give Your Feedback
#diode #diodecircuits #galena #radiofrequency - วิทยาศาสตร์และเทคโนโลยี
Have a question for Derek that would benefit from sharing an image or schematic? Hit him up on the element14 Community: Discuss the episode and ask Derek questions on the element14 Community! bit.ly/3QNKYMF
I was building these in the 1950's. The interest grew and electronics became a career without giving up the hobby aspect. Later on I got my ham Extra license along with a commercial radio license. Well into retirement I still maintain a good selection of parts to use for building electronic projects.
How many people have a hobby as a career?
I remember making crystal radios using 1N34 diodes 60 years ago! I wrapped wire around a cardboard cylinder without counting or calculating anything. My headphone was from a simple kids's tape recorder and it worked. No channel selection, of course, but I could explore the magic of radio. btw, no capacitor was used. I supposed just parasitic capacitance of the wiring formed the tuned circuit. I remember constructing a number of these so your video brought back fond memories.
HI Anthony. Interesting - probably a combination of parasitic capacitance in the winding of the inductor. Inductors are self-resonant because of this. Glad it brought back memories! -Derek
I love the "tinkering" vibe of these videos... you guys experiment on the hardware and the sometimes unexpected results come out
Wow, love reading all these great memories here in. For me, we were introduced to a modified foxhole radio. It used tin foil and waxed paper for the capacitor. The detector was bluing an old straight razor blade and a safety pin. The tuning was very crude; just sanded some of the enamel off the coil and then used a bit of a bean can as a variable tap. So as a kid who grew up with home computers, it was like magic to hear a signal from what was a bit of scrap and kitchen supplies.
That's a great story. I love the idea of using a bunch of MacGyver components to make a radio. I bought a stack of feather safety razors to make a foxhole version, but the project was starting to get out of hand. I would love to take a crack at it still. Maybe in a revisit episode. Thank you for sharing your experience.. fantastic! -Derek
I love your videos and delivery style. You are so low-key and welcoming, yet packed with great information. When I was around 9 or 10, my dad bought me a book of simple electronic projects.. the very first thing we built was a crystal radio-- I remember the crystal and the variable capacitor -- that was the size of a large potentiometer but it had several thin squares of plastic film separated by metal fingers. I don't remember an inductor, but there must have been one. And yes, we had the exact same 'grandpa's ear phone' you had in this video! We mounted the entire thing on a small block of wood, and it worked! I've been building electronic projects ever since.
Can't use the element14 Community because some glitchy sign-in/browser issue. So I will comment here. I really enjoyed your build video. I too have built "crystal sets" in the past but I usually take projects apart once I'm finished to reuse parts - so no pictures!
I had success with making the antenna a 16/18" frame type where it doubles up as the inductor also. I'm suggesting this for people who may have issues with putting up a long wire antenna. Also worth mentioning for the billions of folks that ain't US citizens, in the rest of the world you may find old OA type diodes like for instance OA90 or 91 (and others) that serve in place of the US 1N34 type.
That's not too bad it reminds me of the really cheap am transistor radios you could at the market in the very early 1970s ❤
some alternatives for germanium diode :
silicone diode (0.65v voltage drop) with parallel drained/dead AA/AAA @ 0.6 volt
red led (1.6v voltage drop) with parallel fresh/new alkaline AA/AAA @ 1.55 volt
source: SciToy radio site
Great job, bro! I love the Pu case in the background. It increases your science cred to 11!
Hey Jim. All my gear goes to 11!
The 1N34 Ge diode is a true classic it and the 1N60 I used when I made my first radio receiver back in 1972.
Hi Bob. So classic, I had a tough time finding a legit germanium diode. I ended up with an NTE replacement. -Derek
Super cool! Thank you
I believe that the old radio is using what they called a cat's whisker detector.
From Wikipedia:
"Cat's whisker detectors are obsolete and are now only used in antique or antique-reproduction radios, and for educational purposes. The tip of the wire contacting the surface of the crystal formed a crude and unstable point-contact metal-semiconductor junction, forming a Schottky barrier diode".
Yeah, I think it was because they use super thin wire to make the point contacts. I guess it kinda looks like whiskers.
👍Think Q would come into play more for few turns of tapping 5% of resonate energy into the low imp diode earphones.
I've seen some designs out there that tap off the coil - I'm going to have to look into this. Thanks! -Derek
great job!
Thanks! -Derek
Very enjoyable, thanks ☺
You bet! -Derek
Nice video, great job
Great video, thanks! Seems that there is a lot to learned from these type of circuits. I would like to see what some basic filtering would do. The giant tuning condenser is about 3 times larger than it needs to be, but it looks REALLY cool! I'm glad I've discovered this great channel. Over 100 years worth of technology spread across your shop!
The tank circuit IS a basic filter.
Selamat besenang senang saya menikmatinya.dan saya banyak belajar...awal saya mempelajari radio saya berhasil membuat nya itu adalah dasar radio....
Great video and very cool T shirt!
free energy..!
you know, for a few diodes, a varicap, and a coil of wire, i'm pretty impressed... i'm in no way a microwave RF engineer, but for a few diodes, ... i'm very impressed...
ok thats it, I'll probably give this amateur radio thing a shot .... wondering If I could make an Event badge that works as a crystal radio.
Would you have to wear a crown of wire to pick up a station? 👑
It might be easier to implement an HF morse code rig. Search for tuna can qrp radio. Might make a nice project! Let me know if you get that license, and I'll point an antenna at you. (BTW, you have to post those cool crystal radios in the community) -Derek
Very good thanks!
Nice practice radio for up and coming electronics engineers!
But I have a question absolutely not related to this video.
This is about AC voltage step down, to which I know a transformer is the best option out there, but I've been wondering, what if one could step down voltage using a TRIAC and then employ an RC filter to restore the waveforms at the output!
Eg. Stepping down 220vac to 110vac with an RC filter, will this still output a pure sine wave?
If this its doable your scope would confirm it!
Will you treat this as a subject for your next video ?
sir do you have making video of LC tank radio ?
You have forgot to include the nearfield in your discussion, which is very interesting and has many applications. To study the nearfield of a dipole source, one must solve the inhomogeneous wave equation, ie the wave equation = source term. Solving this equation shows that the phase vs distance from the source is non linear in the nearfield, with minima at the source of the field, and becomes linear after about one wavelength from the source. Applying well known phase speed and group relations, which are inversely proportional to the slope of the curve, shows that the phase speed and group speed are instantaneous in the nearfield, and reduce to the speed of light in the farfield, about one wavelength from the source. The longitudinal electric field and the transverse magnetic field are created at the source. But the transverse electric field is created about 1/4 wavelength from the source and launches transverse electric fields both back toward the source and also away from the source. The electric field from the dipole source circulates from one pole to the other pole. So there is a circulation of electric energy in the nearfield: longitudinal out, transverse in. The transverse electric field and transverse magnetic field are 90 deg out of phase in the nearfield, and become in phase in the farfield, where they propagate together by reinforcing each other. The instantaneous nearfield has serious implications for Relativity and all theories based on it. For more detailed information see:
*Superluminal Electromagnetic and Gravitational Fields Generated in the Nearfield of Dipole Sources - William D. Walker
arxiv.org/abs/physics/0603240
*New Interpretation of Relativity - William D. Walker, Dag Stranneby
vixra.org/pdf/2309.0145v2.pdf
*Superluminal Maxwell Displacement Current measured in the near-field of a spherical capacitor - Emmanouil N Markoulakis, William Walker, Emmanuel Antonidakis.
www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1
I picked up a chunk of galena from an old abandoned lead mine last year, but I've yet to get it to act like a diode. My LCR meter thinks it's a capacitor.
I couldn't make mine work at first when using just an earpiece.. I had to poke around until I found a good contact point - and that was using the curve tracer. There were only a couple of working locations. -Derek
n =#of turns. My grandson wants to know how do you solve for the turns number?
Batteries not included. Wonderfull.
Yes. There's something novel about that. -Derek
AM stations still exist there 😁
Yes, crazy I know! -Derek
Did you try a schotkey diode?
I tried a couple of different diodes, and it didn't make too much of a difference. Of course that's because there's an AM station in my back yard. I'm sure there'd be a significant difference if I was focused on weak stations though. Interesting to note, the schottky diode I did look at had a lot of reverse leakage (for future investigation!) -Derek
Can't log in to element14 😢
Reach out to the team on the feedback and support area and they'll help you get in: bit.ly/42uJLOX
a pin and a piece of coal worked to if i remember, and very low impedance hobby earphone