Crystal Radio, Capacitive Tuning (Update with Annotations Available!)
HTML-код
- Опубликовано: 2 авг 2024
- The BEST crystal radio I have used or built! This radio works very well. I've tried many crystal radio designs with variable capacitor tuning and none worked. (I've got a video on a failed one.) The starting point for this model came from a 1997 ARRL article (based on a design from the 1930's by Elmer G. Osterhoudt) and I've made changes in both parts and construction.
This is now one of my 2 favorite crystal radios. The other is the modified Boy Scout radio. The BSA radio is simpler to construct, cheaper - requires only 2 purchased parts, easier to operate / tune, does not require a significant ground. It gives a loud output. On the downside selectivity is not good; weaker signals are often buried under crosstalk from stronger stations. The modified ARRL 1997 radio is more expensive, and more complex to build. It requires a good ground. Where this radio shines is in clarity of reception, i.e. selectivity - it tunes very precisely and even the weakest signals can be heard without crosstalk. The output is only slightly weaker than the BSA radio. Overall a very good radio.
If you like radio and / or electronics, you might consider joining ARRL (Amateur Radio Relay League). www.arrl.org
MATERIALS
- 1N34a germanium diode (can NOT use substitutes)
- Piezoelectric earphone (can NOT use substitutes)
- 2 x 450 pF variable capacitors (can be air or mica types)
- 10K ohm resistor (can vary to suit your radio)
- Inductor: approx 146 microhenries. Core - 4 inch diameter PVC pipe. Wire - 32 turns, 35 feet (10.668 m) of 0.5mm diameter (23-24 wire gauge) enamel wire. 1.1 feet per turn. 1.1 feet = 33.582 cms. 35 feet = 10.668 meters. Circumference of 1.09 feet = diameter of 4.16349 inches.
3D Printable Knobs For This Radio: www.thingiverse.com/thing:619...
ANTENNA
The best antenna would be 152.4m (500 feet) long. A "good" antenna would be 30.48m (100 feet). The video uses an antenna of only 12 meters (40 feet) and it works OK.
WARNING - Never run antennas over or near power lines or electric wires. Serious injury or death may result. If you don't know, learn or don't do it.
ORIGINAL ARTICLE
"The Crystal Radio", Dave Evison, W7DE, QST December 1997, pp. 56-57. This article's design is based on one from the 1930's by Elmer G. Osterhoudt
OTHER CRYSTAL RADIO VIDEOS
- Best/Easiest DIY Crystal Radio - No Batteries, No External Power 2023 (4K)
• Best/Easiest DIY Cryst...
- A comparing 2 designs, one better than the other
• Popular Crystal Radio ...
- Crystal Radio Powering a Joule Thief
• Joule Thief PLUS Cryst...
- Popular Crystal Radio Design That Does Not Work
• Popular Crystal Radio ...
- New Crystal Radio Design
• New Crystal Radio Design
- World's Simplest (Crystal) Radio
• World's Simplest Radio
- Crystal Radio Improvements & Upgrades
• Crystal Radio Upgrades...
- Connect DC Amplifier to Crystal Radio
• Connect DC Audio Ampli... 
Наука
Remixed version with annotations restored: ruclips.net/video/VJ80Nm9KSkE/видео.html
3D Printable Knobs For This Radio: www.thingiverse.com/thing:6191252
RELATED CRYSTAL RADIO VIDEOS:
Best/Easiest DIY Crystal Radio - No Batteries, No External Power 2023 (4K)
ruclips.net/video/fLVCqZGpv3U/видео.html
My New Favorite! Crystal Radio with Antenna Tuner: ruclips.net/video/mh5KxCpbQ5U/видео.html
Crystal Radio & Resonant Coil Design: ruclips.net/video/Fw9eb-aB-XU/видео.html
Crystal Radio Antenna (Shortwave Also): ruclips.net/video/G8AsgZbncW4/видео.html
My Crystal Radio Does NOT Work (FIXES for common problems): ruclips.net/video/kCxQ8iPQx4s/видео.html
Good Crystal Radio Connection Points: ruclips.net/video/G3qjrReHR1k/видео.html
Crystal Radio, Connect A DC Audio Amplifier: ruclips.net/video/RW3VhnzgjtA/видео.html
Three Upgrades For Your Crystal Radio: ruclips.net/video/LENco3_jV_s/видео.html
Crystal Radio Wiper Upgrade: ruclips.net/video/i1otDz39nlw/видео.html
Popular Crystal Radio Design That's a Waste of Time - And Why: ruclips.net/video/r9Onub2Xpzc/видео.html
New Crystal Radio Design - "Modified-Pickard": ruclips.net/video/_qxHhFKjLAg/видео.html
Crystal Electric Generator RF Energy Harvesting Exp 5 - Full Wave Rectifier: ruclips.net/video/BTu_GJKjOmA/видео.html
In the late 1940s a store on Fordham rd in the Bronx sold a crystal radio for one dollar I would lay under the bed and use the springs the underside of the bed for an antenna and the radiator for a ground ,had lots of fun.
excellent, the selectivity increased quite a lot with the antenna capacitor. Thanks for the information.
Again thank you very much for your information! It is very helpful.
Nice fun. I built my first crystal radio in 1963, using a pencil lead and old penny for a detector. 1N134A diodes are not all the same. Experiment with different ones, and you can find a "hot" one. Once you found your good diode, try wiring a second one in parallel using the same "hunt and peck" testing. Eventually you'll get a real dynamite pair. You can beat the crystal earphone using a large piezoelectric element instead, with an 11k resistor across the audio terminals (helps to try slightly different resistances}. Also, your air variable for your antenna can be substituted with a cheap fixed value ceramic one, once you've learned the correct capacitance, either by measuring the air variable, trying different small fixed value ceramics, or a low value capacitance substitution box. As long as you use the same antenna and ground (same impedance) the fixed value cap will work fine.
Thanks. I will have to try your ideas out.
by the way... I'm gonna build this one in this video also.
thanks for sharing
I have found that many germanium diodes will work with crystal radios (1N270 etc). The main thing is having a very low forward voltage, you can test this with a multimeter
Good job! These simple radios are fun. You are so right about the copyright police. I fixed a 1951 car radio for someone and wanted to show him it working. I posted publicly in case anyone was interested. It got banned in U.K.! I just had to acknowledge the us copyright.
I had to take down several and re-make the video because I left a radio playing in the background. It was barely audible in the finished video, but their detection software caught it. I wish they would tell us what was an acceptable length of time to show things like radios working / being tested. I'm guessing they don't want the risk / responsibility of saying, so they hit us with it.
Same here. I did a video showing how I repaired a Grundig shortwave radio and got banned in Germany for demonstrating how well it played by playing a little bit of classical music from a station. I disputed the banning arguing it was only for demonstration purposes but RUclips wouldn't budge on the banning.
Hi I enjoyed your video. I particularly appreciated your explanation of the physical construction, i.e. mounting the components.
I would take issue with your insistence that only a 1N34 diode will work. I'm not trying to be argumentative and you seem to have more practical experience of radio construction than I. But there are many places in the world where US standard parts may not be readily available. And if you tell people that they cannot build a crystal radio without that specific diode, you may stop them from trying to put something together themselves.
I have built a satisfactory radio using an OA90 diode which may be easier for many to find and purchase. I used a loop antenna with no ground and could receive the three main AM stations still broadcasting in the UK. I am sure there are other diodes that may work albeit perhaps not as well as what you have made.
Again, I liked your build a lot and thanks for sharing the video.
I have no doubt there are other germanium diodes that might work, however when people use the wrong one or believe they can use any diode or use one of inferior quality (there are issues with some Chinese made ones) then I get a whole slew of nasty comments about how it's fake or does not work (can I spend hours helping them fix it?) or ... So if they use the parts and construction as I have described them, then it's going to work and everyone is happier.
Thanks!
Very cool
You CAN use other types of earphones. I use an old rotary telephone earpiece. It works quite well. Also I first used a random diode from a old tv circuit board from the 80s. It worked pretty well. I have now switched it out for an antique germanium diode. It works better than the modern germanium diodes.
The rotary phone earpiece was likely crystal. That type may work better with a capacitor than the resistor required by the new piezoelectric type.
tsbrownie thanks for your reply. Yes it does. It already had a big black capacitor with a red stripe on each side. I just left it. I’m sure it wouldn’t work without it. Also I was testing piezoelectric buzzers and had one from a fire alarm attached when I attached the telephone receiver. For some reason it doesnt work or barely works without both of them attached to the two poles on the back of the phone receiver. I’m thinking maybe the buzzer piece possibly amplifies the minimal voltage coming through. I can, as you said, tap the buzzer piezo and here it on the telephone one. I can’t hear a thing without both of them wired together. Even then I can’t really hear anything through the buzzer. Any ideas? Thanks!
The piezo buzzers I've played with were used with active drivers, they required a lot of power relative to the earpiece from your telephone. If you have a meter, try to measure the power from your crystal radio, I think you will find it to be tiny, tiny. Radio signals act a lot like static electricity compared to low voltage 60 Hz AC. So there's 2 things going on, very tiny currents and that high frequency AC static-like thing. I don't know which style of radio you are using. The components you add can drastically affect the "tank circuit" (resonant circuit) and overall resonance of the system (even your hand / body near parts of it can improve or lessen performance). It's another reason that earbuds from your phone won't work well (that and they require power). A crystal radio is a balancing act of the tank circuit (RCL of those components) and antenna / ground (with its resonance) where efficiency of the overall system is king. That's what makes it interesting and challenging.
When mounting the capacitor a lot of times I hot glue them to the board. Just make sure don't glue the fins.
hello sir. I must first thank you for sharing your knowledge and time; and for the great effort you input toward clarity and simplicity for the viewers/ learners understanding. your video on the modified boy-scout is from which I built my 1st crystal radio - and it work🤣. even tho I didn't have the best antenna. so thank you.
I'm writing to ask if you know of any fairly simple to build 'FM' crystal radio?
I tried one, with no success. even bought sterling silver wire to make it. anyway, I'm very good at following good instructions, and have a low, to medium level electronics building skills.
hope to hear from you soon. thanks again👍👍👍👍👍
It would be extremely difficult to make an FM radio that operates on the power from the radio signal. AM works by changing the power of the signal, so you can easily detect changes in the power with a simple circuit. FM changes the frequency of the signal. That's really hard to detect and demodulate with simple circuitry because you need to measure the frequency, then determine the shift.
ah ok. thanks for the reply
Actually, there *is* a way to detect FM with only an AM circuit. (I don’t know if such would work with a crystal set, but maybe so.) The name for the method is “slope detection,” and it’s very easy: Using a regular AM detector circuit, tune slightly off-channel. (Here, I assume that you’re tuning *below* the normal channel.)
The theory: FM works by varying the carrier frequency. When the signal is strong, the carrier deviates further. When the signal is weak, the carrier deviates only a little. To a purposely mistuned AM detector, strong signals come in weakly. But the weak signals are close to the normal channel. These signals come in strongly.
In short, the strong signals detect weakly, and the weak signals detect strongly. Inverting the signal this way makes no difference to the ears. (There *would* be a difference if the signal were video: Because the output would be negative. In that case, I suppose that one could tune *above* the normal channel.)
Slope detection has none of the high-fidelity advantages of FM detection. Instead, the slope-detection advantage is bang for the buck: Simplicity, economy, and ease of building. Best of all, slope detection works well. (Again, the “contrary” idea is true: The weaker circuit becomes the winner.)
Another simple circuit that can detect FM well is the super-regenerative circuit. (Few people remember it. And it’s not the same as a regenerative circuit, should you ask. Back in the day, Radio Shack used to sell regen “P-Box” kits. You can look up schematics for these kits on the Web.) Godspeed, experimenters!
Thanks sir...
Try Bordens radio company ,and Mike's electronic ,both specialize in stuff for crystal.radio,and farnstock clips I probably spelled that wrong ,those little clips like you are using getting hard to find when you do they are pricey.what gauge magnetic wire are you useing.also one of these places I got some vintage diodes there were using way back then ,they also sell military grade diodes ,I got a couple of each haven't tested them yet I also have the one you are using ,because they are the most popular .where did you buy your variable running calculators ,it would be nice to have new ones ,I have the ones from the transistor radio type you shown .I haven't even built mine yet I been collecting components for six year,I want to find a simple design for not scouts,that works.
Is that a Fessenden's heterodyne radio receiver circuit? There should be a way to hook the two variable capacitors to adjust according to each other to make the tuning more simple .
This is based on a design from Elmer Osterhoudt. There is probably another design out that with simpler tuning, but I've not found it yet. If you look at this design you see that both variable caps are affecting the resonance, one more than the other. One is affecting the antenna matching more, but in a crystal set everything from antenna, to radio to ground is affecting resonance! ;)
Hi!
Thanks for sharing this!
-Can i use a double-capicitor? -bad idea? -if it is: -why / how?
-Which frequences does it recive?
-How do i make it recive higher / lower frequences?
-Should i have the antenna straigth up? otherwise i have to have it's side to transmitter, don't i?
Double capacitor? You mean more capacitance? What are you trying to do? You can experiment, it won't hurt anything, but it would lower the operating frequency. This version receives the US AM band of about 540 KHz to 1.6 MHz. (Note: This ONLY works with AM = Amplitude Modulation) There are free web pages that tell you the resonant frequency of an inductor / capacitor circuit.
Antenna is run horizontally for as far as you can. For safety keep far away from power lines. Don't use it/take it down before lightning storms.
Thank you very much for sharing! Just wanted to find out how many watts that you use for your resistor: 50 k ohm? Thank you very much in advance!
Thank you for watching. It's a 10K ohm resistor (can vary to suit your radio). Any wattage will do, the power involved is very tiny. The other information is in the description.
1 kw 😀😀😀😀😀Out put of this type radio reciever only few mili watt,any watt risister you can use
nice one, please tell me where can i find the 450 pF variable air capacitors ?
didn't find it on ebay,amazon....etc
The 365 will also work. Google Capacitor - Variable, Single, 365 pF, CW Rotation on Amazon. They are $14 each, but they have them. I found my in a local store that's selling off all the junk in their storeroom from when the previous owner had it. That's another way to find them, old shops that still have old parts.
Oh and you can also use the mica variable capacitors, they run about $4, but the lower range is more limited.
thanks for the info and sharing your research. cheers
you can get these variable capacitors in one gang two and three at (Antique Electronic Supply) on internet .or.Tempe Arizona USA ..6221 S Maple Ave. Zip 85283 Ph # 480- 8205411.. Hope this helps.
Oren Elliot Products. Largest manufacturer of air capacitors.
3:01 1N60 diode also works good.
The only mini variable capacitors I can buy are 0-160pf will it still work what's the worst case scenario ? would there be a workaround ? I am planning to build this radio as its compact and mount all components inside the coil as you described thanks for posting
There's no simple answer to what you want to do. For capacitors you can always put them in parallel to get more capacitance. That would require 4 to emulate this model. It is possible to completely re-design the radio changing the coil to adapt to the capacitor's range. Note that if you change the size of the coil, all the parameters would need to be re-spec'ed (turns, spacing...) to compensate. I've been thinking about how to do a workable miniature crystal set using a ferro slider, (that has many similar consideration) but most designs get only 1-2 stations, not very interesting.
Mantap dan keren 😎😎😎😎😎😎
the hardest things to hold off are the variable capacitors , plus if you do find one, they are expensive,
I wanna see a crystal radio video where the builder does not use a variable capacitor.
OK, here are 2 with no capacitor. Both work well. One is more complex than the other.
ruclips.net/video/mh5KxCpbQ5U/видео.html
ruclips.net/video/mt-s7pf-U5Q/видео.html
What would be lovely is to see the resonance curves for the two different systems
You are right. Let me ponder how I might do that.
Hay on the modified radio you those Capacitors. To me they look like tuners are they a tuner but the Correct.name is called capacitors and also is 1 for AM Radio and is the other for FM radio I'm just Curious is all. Thanks Ray 😊
No, it's only AM. One capacitor is for tuning the antenna, the other is for tuning the radio. But in fact, they both do a little of each.
for the Variable cap mount. Solder long copper legs turn them 90* and bend the ends into a loup screw into the wood |___|O
You never did say what gage wire you were using , it'll change the uh of the coil . What about turns and taps ?
Details are in the description. The wire is 0.5mm
Could you explain the reason for tapping at 9 turns? Why not just wind the coil 23 turns? Is there something special about a ratio of 9/32 or 9/23? I assume there is a reason for this, but it's not explained. Thanks.
I'm not an expert on analog signals, so it's just a guess. From the diagram the headphones are "stealing" a bit of power from the tank circuit (the left side capacitor and the coil) to operate. Too much and the tank circuit won't oscillate, too little and the headphones don't have enough power to operate.
this crystal radio was originally described in QST Dec 97. In a subsequent article titled "Crystal Radio Tips" in QST Aug 98, the author stated that the position of the tap was set in the circuit to match the impedance of the headphones he was using. in his case, they were 2K phones and he used a tap at 9 turns. other phones may require a different tap position depending on their impedance. Dave Schmarder of makearadio.com uses the same technique in many of his circuits he outlines on his web site. Al
What are you using for an antenna ? The usual Boy Scout wire out the window. :)
Actually, yes, but along the roof! I unwound an old florescent light ballast (nasty job, a regular transformer is better).
Antenna wire on insulators to the roof and to a telefone pole. 60 to 100 feet long
Not much of a demonstration of radio stations or was that the only one you received?
If I play more than about 3 seconds of other people's content, RUclips sends me a take-down notice. The original version (since deleted) had only about 7 seconds and multiple stations.)
What are the specs on the tiny variable caps? I can't seem to find a 360pF small plastic variable cap.
Not sure what you mean. The specs for the stuff I used is in the description. Let me know if you have questions.
@@tsbrownie i've searched for 450pf mica variable capacitors and i'm not finding anything that looks like what you've got there as alternatives to the air type. Any tips would be appreciated. Thanks!
@Joel Ohmer In theory any adjustable cap in that range would work, but I won't say for sure because I have not tried it myself. Yes, with digital radios, analog parts are getting hard to find. Ham radio flea markets, old radio repair shops (that is where I found mine), online, old junk radios at garage sales, ....
A 1n60 diode works well also!
Are you sure? Have you tried one yourself? I'm reluctant to suggest anything other than something I've tried myself. I get a lot of "trouble shooting" comments where people have substituted parts that don't work (well).
I guess you could use hot glue to mount the air caps.
Great job, what gauge wire is that?
It is 0.55 mm or about 23-24 gauge wire. It's not terribly critical.
@@tsbrownie does wire diameter matter?i heard that you wanna have the least possible resistance in these,so would it play a role if the wire was thinner(0.15 mm)?
@@ludost5178 Yes, the number of turns per inch (or centimeter) changes the inductance. There are online calculators for designing your own coil, and I have a video on that.
@@tsbrownie i know that,but i mean the wire diameter,not the coil diameter,i made a few of them and you do get some reception,but will making the wire thicker make the signal reception stronger?,as i use 0.15mm wire.
@@ludost5178 Yes, I am talking about the wire diameter. Please look at the coil calculators, you will quickly see what happens with different sized wires. There are 3 interacting parameters, change 1 and the other 2 must change to get the same output.
the varble air cap are not that hard to look for them
500 pf is fine!
What is the wire gauge. Thank you.
Saludos desde Chile.
Hi. The details are in the description. I think the wire was 0.55mm.
@@tsbrownie gracia. Thanks
Nice concept, and a good video. But I wish you had actually shown how to hook the tuning capacitors up, instead of just showing the circuit diagram and verbally explaining it.
Not sure what you mean by how to hook them up. There's a circuit diagram at the end. In the video I show the connections. Can you be more specific and I can try to explain better.
Circuit diagrams are nice, But schematics are somewhat abstract. I was thinking it would have been a bit nicer, If you had shown the part where you actually hooked the wires up to the capacitors, instead of talking about how to mount them and then suddenly we see the wood mounting fixture, already in place, and then we heard, "now the capacitors are installed...".
It may seem elementary to those of you who have done it, and are more advanced in the reading of schematics and such. But it isn't that easy for us ":dummies"!
I agree I could have done better at showing the capacitor connections. You can barely see it at about 8:20 and 11:16, but it's not obvious unless you already know what it should look like.
So in words, the "frames" of the 2 capacitors are connected together electrically (variable plates). That's the diagonal copper wire you see between the caps.
The static plates on the upper cap connect to the grey wire (bottom middle) that goes to the antenna clip. That same diagonal copper wire also attaches to the coil at the front (closed) end of the radio.
The static plates on the lower cap go to that black wire on the right side that runs to the ground clip and to the coil connection closest the back (open) side.
SUMMARY: variable plates connect together, run to front of coil.
Top coil static plates go to antenna clip.
Bottom coil static plates connect to back of coil and to ground clip.
That is all. ;)
Awesome! it was exceedingly nice of you to go into such a lenglthy and detailed explanation! Thank you very much! I love your videos!
How dose it keeps playing
It uses the energy of the radio wave to power the earphone. It's a very tiny amount of power, but it is enough.
Surprised that the metal of the variable caps didn't throw your coils out of spec, or threw them in spec?
Good observation! Yes, I wound the coil, then cobbled it together with the caps in and out to see how it would affect the performance. I was surprised that it made very little difference. My backup plan was to make the base bigger and put them outside the coil.
@@tsbrownie That's very surprising to me. Are they a non magnetic metal? Or maybe the flux density is so low that the metal didn't 'get involved' for lack of a coherent/intelligent term. Maybe they are just the wrong shape to be a core. Thanks for the response, I'll add that to the list of things to wonder about when I should be sleeping.
@@clytle374 They are magnetic. I think it's the flux density is tiny. Go to sleep, it ain't worth it! ;)_
The two capacitors are on the same conductor.
I don't understand. There's a diagram at the end at 16:21 use the resistor between the earphone leads for newer piezoelectric earphones.
@@tsbrownie Sorry I am wrong, one is on the ground and the other is on the antenna. That is correct
@@marynollaig4124 One is across the coil, the other is in the antenna line. How is your build coming?
**=** It's more powerful then older version?
Not more powerful, but better at eliminating interference.
what kind of antenna are you using? a loop antenna?
I always use a long straight wire. I don't think a loop would pick up enough signal to work well. I might have to try that to be sure
@@tsbrownie how long is your wire?
@@freedomer342 One is 15 meters, the other 9 meters. They are 90 degrees to each other so I can get better tuning for stations from different directions. This is my video on a basic antenna: ruclips.net/video/G8AsgZbncW4/видео.html
@@tsbrownie how exactly is the diode connected to the circuit? is it connected to the tap of the coil?
@@freedomer342 @ 16:21 there are diagrams. Yes, it connects to the tap.
In punjabi
This type of work
Called
BOUNND PANGA
I can't find a translation for that. What does it mean?
Can you use any germanium diode?
No, I've tried all the ones in my parts box and only the 1n34a diodes work.
@@tsbrownie So that must be my problem...I have tried many many times to use diodes from 60's 70's radios that I scraped..
@@kennynvake4hve584 It's not the era the diode was made, but the diode type that is important. The 1n34a is very, very efficient and works with extremely tiny voltages / currents. I've got a video about the world's simplest radio, that's just one of these diodes and an earphone attached to an antenna.
@@tsbrownie that is awesome...I have played around with every single config there is...and while I can hear very faint signals I just never have gotten it the way I think it should be...the fact I didn't use a 1N34a diode might be the reason for it not working properly. I have a copper pipe in the ground with a wire to the radio..and a 50 foot longwire out the window to a tree branch..
@@kennynvake4hve584 Give the 1n34a a try and let me know how it goes. I think you will be very surprised. The only time I've had anyone tell me it did not work was a guy from India who said all the AM stations had been converted to digital AM (which won't work).
Are both capacitors 365p?
Yes they are.
Thank you.
W7DE's article www.arrl.org/files/file/Technology/tis/info/pdf/129756.pdf
You have a very nice circuit schematic that you have failed to show us in full screen detail , nice presentation otherwise.
28K people watched this without diagrams! Ouch. Thanks. I've included the diagrams, uploaded it as new and checked to make sure they are there! ruclips.net/video/VJ80Nm9KSkE/видео.html
Must be a chinese capacitor. Really awful quality.