Crystal Radio--No More Variable Capacitor Designs? (4K)
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- Опубліковано 12 січ 2024
- I've wasted a lot of time and money building single variable capacitor crystal radios. They just don't work. If this one does not work, it's the last one I'm going to build. I'm done with them!
I found this design on the internet. It's from the 1950s, rather late in the game (many were from the 1920s).
MATERIALS
- 1 x 1n34a diode
- Board (Mine is 18cm x 12cm)
- 1.25" (1.65" actual) PVC pipe (42mm) x 140 mm long
- 20 gauge wire (0.81mm)
- 16 brass or stainless screws
- 10 brass washers
- 2 pillow blocks (wood or plastic)
- 1 10-365 pF air tune capacitor
- 1 bracket for capacitor
- 2 Fahnestock clips
- 1 resistor 10k-40k ohms
- 1 crystal earphone (piezoelectric)
3D Printable Pillow Blocks: www.thingiverse.com/thing:643...
3D Printable 360 pF Variable Capacitor Mounts (2 types): www.thingiverse.com/thing:643...
TOOLS
- Screw driver
- Knife
- Sandpaper (small piece, fine)
- Saw, if you do not have the wood & tube already cut
- Hand drill for screw holes
- (Optional) Soldering iron, solder
ANTENNA & GROUND
- Antenna are just a long piece of wire (I use scrap wire from old transformers). The longer the better.
- Try different lengths and orientations (vertical, horizontal)
- A good ground helps. A wire to a ground rod is good. Metal water pipes also work well.
NOTES:
- The resistor is necessary to get the best sound from these "new" crystal earphones. The new ones are piezoelectric and have lots of capacitance. Without the resistor the charge builds up then discharges so you get constant "static" sounds. The resistor bleeds off charge so you get louder, and much clearer sound.
WARNINGS:
- Never connect radio to any source of power. Not house current, nor batteries, nothing!
- Never use the radio during lightning storms.
- Never run an antenna over or near power lines.
- Disconnect antenna and put lead outside when not in use.
- Never ground to electrical items, plugs or similar.
- If you don't know, don't do it.
OSCILLOSCOPE USED:
$25 Color Oscilloscope! The Incredible DSO138 (4K) • $25 Color Oscilloscope...
Using The $25 DSO138 Oscilloscope - Joule Thief & Freq Generator (4K) • Using The $25 DSO138 O...
INTERESTING LINKS
Knob For Variable Capacitor & Similar (D & Round Shaft Versions) www.thingiverse.com/thing:633...
- Knobs for capacitor tuned crystal radio. www.thingiverse.com/thing:619...
- Air Core: www.circuits.dk/single-layer-a...
OTHER CRYSTAL RADIO VIDEOS
- Popular Crystal Radio Design That Does Not Work • Popular Crystal Radio ...
- World's Simplest (Crystal) Radio • World's Simplest Radio
- Good Crystal Radio Connection Points • Good Crystal Radio Con...
- My Crystal Radio Does NOT Work (FIXES for common problems) • My Crystal Radio Does ...
- Crystal Radio Fake 1N34A Diodes! Easy Test (4K) • Crystal Radio Fake 1N3...
- Crystal Radio DIY Cat Whisker--Wood, Brass, Stainless (4K) • Crystal Radio DIY Cat ...
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- PSA: Crystal Radio Coil--Bad Plastic Pipe Pt 3--Type That DOES NOT Work! • PSA: Crystal Radio Coi...
- Popular Crystal Radio Design That's a Waste of Time - And Why • Popular Crystal Radio ...
- Crystal Radio, TV, Oscilloscope, Etc Knobs 3D Print • Crystal Radio, TV, Osc...
- Crystal Radio 3D Printable Parts (4K) • Crystal Radio 3D Print...
- Connect DC Amplifier to Crystal Radio • Connect DC Audio Ampli...
- Crystal Radio, Capacitive Tuning - WORKS GREAT! • Crystal Radio, Capacit... - Наука та технологія
My Grandfather, who was born in 1898, used to build these "Simple Crystal Type" radio receivers way back in the 1920's! And, since "Stations" were then "few and far between", getting only two or three "was normal"! 😅
A compromise between a wiper adjustable coil and the fixed coil and variable capacitor designs might be to use a coil with multiple tappings towards one end of the coil and a small variable capacitor around 50pF maximum. This would maintain a higher Q for the tuned circuit while possibly being easier to make. Crocodile clips could be used to connect to the taps on the coil. My uncle made us a crystal set back in the 1950s which had dozens of taps on it together with a fixed 500pF mica capacitor, but I found that only the taps towards one end of the coil were useful for Broadcast Band (Medium Wave) reception. As I learned more about radio, this tapped coil, used with smaller capacitors, was very useful when experimenting with short-wave reception.
My first crystal set had a variable inductor "loopstick". I listened to it every night. The loopstick was only .25" in diameter and the ferrite slug went in and out to tune it.
Very nice. Helps explain just what I didn't know in 1965. And also, why I just had a lot of "fun/frustration" fiddling around with electronics. I had no teacher, just a kit-ish, or old radio like looking stuff. 🤣
I've built a few crystal radios using both the slider coil and variable capacitor (taken from an old portable radio). It worked a lot better than I anticipated.
Add a series LC tank from ant to ground and tune out interfering stations.
Use good ground and a long, long wire .
Consider using loop sticks.
Well done presentation.
That takes me back about 50 years. my first crystal set on a block of wood and a bit of crystal stuff as the detector. Thanks for the video and i look forward to the upgrade.
Cheers Dave.
Thank you. I did my first crystal radio for cub scouts from the handbook. That was almost 60 years ago. Used a toilet paper tube, wire from a transformer, and a piece of galena. It's still magical.
Variable inductor, and jfet detector may be nice to try? Also use a 18 henry or at least one henry inductor across the piezo ear phones. Water pipes make a good ground and you can use a tv antenna for am as well or one or both sides combined. Or a split antenna version. If you use a Jfet maybe an antenna to the gate and one to the circuit with common ground. With maybe a coupling 10pf capacitor in the circuit. Maybe a voltage multiplier to the piezo as well.
So glad that you had success. Bravo! I get it; non-success (which is different than failure) just ain't much fun, sometimes.
So true!
Thank you so much for making these videos- Ive learned so much from watching your builds & a few others, and finally felt comfortable and encouraged enough to build my own crystal radio. I did a 25 turn antenna coupled to a tuning coil (same tube about .25" space between the two) with taps. Bottom of antenna coil and tuner coils are grounded, as are one side of my earpiece and one side of 47k resistor. Other side of resistor is connected to other side of earphone and cathode side of diode, anode side of diode to one end of alligator jump clip, other side of the aligator clip on the taps for tuning. The top of antenna coil isnt connected to anything, and the top of tuning coil is connected to antenna wire. I built this with extremely little knowledge of how circuits work other than watching videos and borrowing a copy of "electronics 101 for dummies" and doing a quick read through that, so I played around with it lots to figure it out, but it works great- I pick up my nearest AM station during the day (loudly!), but at night I pick up a few (much quieter) shortwave stations that broadcast internationally (at least one is +550 miles away) so I am quite pleased! I just salvaged a dual air varcap (and a few other interesting, if not useful, parts) from an old tabletop tube radio and was wondering if you might tell me where I should connect it in the circuit? I assume it should take the place of the jumper clip (currently from diode to taps), but do I need to incorporate each of the capacitors individually? And if so how would I do that? One varcap connected to first tap and other connected to last tap? Any advice would be appreciated 😊
You are welcome. Glad you got it working so well. Have you watched this video on using a dual gang cap?
ua-cam.com/video/EqEVuLFxgCQ/v-deo.html
Maybe it's what you're looking for.
Thats exactly what I needed, thank you! 😊
Very informative, Thank you for sharing
My pleasure!
Thank you for the videos i enjoy them very much. I think if you would wind a nice loose coupled coil, you would get the performance your looking for from a cap tuned set. I did and it made all others obsolete.
Nice multi-Station tunable crystal Radio...Well done !! ....You could connect a Fixed tuned Parallel LC tank "Trap" circuit in Series with your Antenna wire...Fine Tune the L or C to Resonate & "Notch" out your strongest Offending station & Move the diode Tap farther "Up" the Tuning coil for max volume on Wanted stations....
Also: If you use a tuned loop antenna, you can turn the null point of the reception pattern towards the offending station.
Knowing that I lack some basic background info, this did help for the variable capacitor. What through me off was not thinking it worked was because of a loose bottom chassis wire connection. Soldering doesn't seem to hold so I just used a piece of masking tape on the side of the chassis. I rubbed down on the tape, and the circuit worked to get two stations at very low volume.
Thank you
If the solder won't hold, it's very likely the wire has not had all the insulation removed. A dirty connection could cause the low volume.
@@tsbrownie audio is good quality with better antenna reception for the two local radio channels. I'm very pleased with the results.
@@Paul-ki8dg Well, good. The antenna is supplying the power, so a better antenna means better output.
Hi , I like the circuit because it appears to include an antenna / load impedance matching circuit . typical crystal set needs Hi impedance phones so as not to load down the Antenna . I've built a crystal set with an OA91 diode , Hi Z phones and a 150 foot long wire antenna Long time ago . The next step up from simple crystal set receiver would be a T.R.F. ( tuned radio frequency receiver) or a Regen circuit . Or you could just bang an audio amp on the output of your crystal set so it can power a loudspeaker . 73's DE G4MXC .
I like it for the same reason. That and it actually works! I have a video on putting a low cost audio amp on these. ua-cam.com/video/RW3VhnzgjtA/v-deo.html
My antenna is only 9 meters or 27 feet.
Be sure to use a germanium diode instead of silicone for more sensitivity.
Yes many use silicon diodes and expect that to work, in fact all 1N34 germanium diodes are not equal some of the same part number perform better than others, try a few different ones to find a hotter diode
@@johncherish7610Yes, I have two real 1N34 diodes and one works about twice as well as the other.
Really nice video clearly explained. Thanks.
The scope your using looks interesting any details or a link to it ???
Thank you. The scope is can be seen in these 2 videos:
$25 Color Oscilloscope! The Incredible DSO138 (4K) ua-cam.com/video/I5jvzTOeHKc/v-deo.html
Using The $25 DSO138 Oscilloscope - Joule Thief & Freq Generator (4K) ua-cam.com/video/6og4H4boWVo/v-deo.html
I wish I had had one when I started experimenting with electronics. Back then even a cheap scope from the flea market was WAY out of my budget!
Cool experiment.
Thank you! Cheers!
Thank you for your videos, they have gotten this old farts interest back into building again.
Glad to hear it! Let me know if you have questions.
❤❤❤❤❤
Hey, so I want to use these concepts to energy harve ULF and ELF, specifically I want to experiment with energy harvesting the noise floor at 5 KHz and lower, avoiding 60 Hz of course, I don't need to go to jail lol.
What would you recommend? I"m going for those frequencies because I noticed that the noise floor at those frequencies can be as loud as broadcast in higher frequencies in terms of dB.
Higher frequencies have a LOT more energy to harvest. I think by the time you get to ULF and ELF you might as well put a cockroach in a hamster wheel. I don't know of any laws about harvesting 60 Hz, as long as you stay a certain distance from power lines. If you harvest it from your own house, it will show up on your electric bill (no free lunches). I just ran the numbers on an LC calculator, and for 5 KHz you only need 100 uF and 10 uH. That's not hard to do. It's making an efficient antenna. Often they are quarter wavelength. The ULF wavelength is 1,000 to 100 KILOMETERS. ELF wavelength is 100,000 to 10,000 KILOMETERS. I wanted to build a radio to listen to the Sun's output, but the amount of wire needed for the antenna was prohibitively expensive.
HI. How about having a series varicap on the antenna wire to tune the antenna. Thanks for great videos.
I did this one: ua-cam.com/video/VJ80Nm9KSkE/v-deo.html
You can see it at 02:49.
How about a surface mount radio, using multiple array
Your coils look beautiful. But, there is a big but : there is a lot of capacitive coupling between individual windings.
I used to build these as a youngster. Nowadays it is hardly any fun since the high power Medium Wave transmitters are now doing DAB only.
I am in the Netherlands btw
🤝🏻
Thanks. The capacitance is included in the resonance calculator. It's 1 reason there's not the capacitor used in old radio designs. DAB is a problem.
Dear nice video. I have seen people on youtube designing portable AM crystal radios with magnetic loop antenna with optional ground and the main coil coupled with it by placing it right in middle of the loop antenna. The magnetic loop antenna was square type with each side 24 inches in length having 11 turns of 22 AWG wire each loop having gap of 0.5cm to achieve Q factor. The loop antenna was 204uH. And the ground was optional. no long wire antenna etc. And fun part was using a step down transformer for impedance matching at Output which was available on a large 8 to 20 Ohms speaker without any external power supply or amplifier. Of course to drive the large speaker good ground was necessary. Otherwise for a high impedance earphone the radio did not require ground connection. Can you comment on it please the one with loud speaker and magnetic loop antenna. Thanks in advance.
I'm working on a loop antenna version. I bought most of the stuff needed but it turns out some of it is wrong, and I need some more learning to get it right.
Thanks 👍
Thank you.
@tsbrownie What should be the coil wire gauge. I am about to buy and would like to have some help in deciding .
Thanks
The details are in the description. Also I did a vid on coils that might interest you.
Is it possible to make this radio with a 14-178pF tuning capacitor and 28 guage magnet wire? If so, what changes would I have to make to the design?
That's pretty much a complete, untested redesign. But, if you had 20 AWG wire and made the same coil as shown, you could use that variable cap wired in parallel via a switch to a 180 pF capacitor. It would divide the band into 2 pieces (14 to 178 pF range, and with the fixed cap 14 + 180 pF and 178 + 180 pF). With the fixed cap in the circuit, it would tune the lower part of the band. With the cap switched out, you'd be tuning the upper part of the band. That was a common way to do things in older radios. In fact they had removable coils for different frequency ranges. If you want to design from scratch, my 2 favorite free playstore apps are "Electrodoc" and "LC Circuits."
I don't know where you found those variable capacitors but the shipping these days cost more than what you paid.
Have you tried using a signal generator injected into the antenna leads set at both the low end of the AM band and at the high end of the AM band?
You could then adjust your variable capacitor to maximize the signal at those two extremes and measure the capacitance.
These two numbers would let you pick a variable condenser with a range that's fine tuned for this design and that might also give you more selectivity without the need for gear reduction.
This is all a guess as I have no electrical training or degree.
The problems I see with the corroded old vintage tuners is they might not be consistent across their entire range due to oxidation variances on their plates. Again; not checked but a guess.
I bought them years ago. I think I've used them all up and will have to buy more. I just googled them and found them from $25 up. Ouch.
Yes, I have used a scope and signal generator to check out the circuits, resonance frequency, etc. Also checked that against the online calculators.
Old caps can have a lot of problems, the most common being plate damage / bends. I've kept these well packed.
have you given up on the energy harvesting transformer from the ambient?
No, I'll never give up. Just have not thought of anything new that would be interesting.
If someone had the time and made 500 of those coils, placed them on a wall to generate electricity, has anyone tried that?Would each coil need it's own antenna wire?
I can't answer the first question, but for max power each would need an antenna.
Direction turn a coil is free? 132 turn which one add 2 turn? Is it sw frequency? thank you
The direction does not matter. It is AM.
@@tsbrownie ...can I use 42 mm tube diameter?
You should broadcast your own content for "legal" playback. 😊👍
You must have read my mind, I'm working on that!
Why wouldnt YT allow you to put the sounds on here?
It's copyright infringement and everyone wants to sue to get money. UA-cam does not want the liability and costs associated with the law suits.
Gotcha, I thought that as I was typing the Q but figured I would allow it to stand and see if thats the case. Its insane man because CR laws clearly show we SHOULD be able to use clips of songs as a form of Fair use but nope, 3 notes in a row that sounds similar to something from 30 years ago and record label copyright trolls will come out from under their bridge instantly.@@tsbrownie
@@seditt5146 Several years ago there was a German company that filed strikes against every one of my videos for infringement on their "songs" and other. They demanded a small payment for each to clear them. In one of the few cases of UA-cam listening to a small channel, I wrote and told them this was extortion-by-lawyer because all my video content was written, directed, produced, videoed, voiced, and "acted" by me. They just wanted money to go away. UA-cam sided with me and I never saw that company anywhere again. Now it's just the big guys that channels have to fear. ;(
Now make it FM
Easy , slope detection.
I use this. Type. Of. Variable. Coil. In crystal radio. ..in. 1968. ...working. Very. Well with. OA 79. Germanium. Diode. And. Miltery wireless. Headphone