Crystal Radio--No More Variable Capacitor Designs? (4K)

[@robinj.9329]

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"! 😅

[@cncdavenz]

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.

[@tsbrownie]

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.

[@billsutton5542]

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.

[@randolphfriend8260]

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. 🤣

[@t1d100]

So glad that you had success. Bravo! I get it; non-success (which is different than failure) just ain't much fun, sometimes.

[@tsbrownie]

So true!

[@blacksmock445]

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.

[@CharlesFeazelle]

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?

[@tsbrownie]

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."

[@barefootthruthemtns]

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 😊

[@tsbrownie]

You are welcome. Glad you got it working so well. Have you watched this video on using a dual gang cap? kzbin.info/www/bejne/e6Koh6iCe92aebM Maybe it's what you're looking for.

[@barefootthruthemtns]

Thats exactly what I needed, thank you! 😊

[@chaorrottai]

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.

[@tsbrownie]

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.

[@NHaq-e7d]

@tsbrownie What should be the coil wire gauge. I am about to buy and would like to have some help in deciding . Thanks

[@tsbrownie]

The details are in the description. Also I did a vid on coils that might interest you.

[@kf5hcr176]

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.

[@justtinkering6713]

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.

[@BobEwald-hw5vx]

I just built this and it works great !! I wonder if the selectivity could be even better if you added a varable capacitor on the smaller antenae circuit ( the 20 turn ) loop. ? That is my next try.

[@tsbrownie]

Interesting idea. Let me know how it works.

[@YusupYusup-ez8qn]

Direction turn a coil is free? 132 turn which one add 2 turn? Is it sw frequency? thank you

[@tsbrownie]

The direction does not matter. It is AM.

[@YusupYusup-ez8qn]

@@tsbrownie ...can I use 42 mm tube diameter?

[@patomahony9747]

Really nice video clearly explained. Thanks. The scope your using looks interesting any details or a link to it ???

[@tsbrownie]

Thank you. The scope is can be seen in these 2 videos: $25 Color Oscilloscope! The Incredible DSO138 (4K) kzbin.info/www/bejne/f2bNp62KhMp7gcU Using The $25 DSO138 Oscilloscope - Joule Thief & Freq Generator (4K) kzbin.info/www/bejne/bKDKZXtql9SKjNE 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!

[@raydan18]

have you given up on the energy harvesting transformer from the ambient?

[@tsbrownie]

No, I'll never give up. Just have not thought of anything new that would be interesting.

[@Paul-ki8dg]

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

[@tsbrownie]

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.

[@Paul-ki8dg]

​@@tsbrownie audio is good quality with better antenna reception for the two local radio channels. I'm very pleased with the results.

[@tsbrownie]

@@Paul-ki8dg Well, good. The antenna is supplying the power, so a better antenna means better output.

[@Onesfear]

Very informative, Thank you for sharing

[@tsbrownie]

My pleasure!

[@philipmetzner7243]

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.

[@travismoore7849]

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.

[@tomstrum6259]

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....

[@kensmith5694]

Also: If you use a tuned loop antenna, you can turn the null point of the reception pattern towards the offending station.

[@haraldlonn898]

HI. How about having a series varicap on the antenna wire to tune the antenna. Thanks for great videos.

[@tsbrownie]

I did this one: kzbin.info/www/bejne/jHubYYGjbrCGoac You can see it at 02:49.

[@Havilah_Springs]

Thank you for your videos, they have gotten this old farts interest back into building again.

[@tsbrownie]

Glad to hear it! Let me know if you have questions.

[@Plons0Nard]

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 🤝🏻

[@tsbrownie]

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.

[@chrisspeakman7215]

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 .

[@tsbrownie]

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. kzbin.info/www/bejne/iIiWh5ukr8ydqqM My antenna is only 9 meters or 27 feet.

[@adnacraigo6590]

Cool experiment.

[@tsbrownie]

Thank you! Cheers!

[@tenlittleindians]

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.

[@tsbrownie]

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.

[@markhodgson2348]

How about a surface mount radio, using multiple array

[@billryland6199]

Be sure to use a germanium diode instead of silicone for more sensitivity.

[@johncherish7610]

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

[@kensmith5694]

@@johncherish7610Yes, I have two real 1N34 diodes and one works about twice as well as the other.

[@seditt5146]

Why wouldnt YT allow you to put the sounds on here?

[@tsbrownie]

It's copyright infringement and everyone wants to sue to get money. KZbin does not want the liability and costs associated with the law suits.

[@seditt5146]

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

[@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 KZbin 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. KZbin sided with me and I never saw that company anywhere again. Now it's just the big guys that channels have to fear. ;(

[@bob_mosavo]

Thanks 👍

[@tsbrownie]

Thank you.

[@YEMinThant-gv1my]

❤❤❤❤❤

[@normandothegreat]

You should broadcast your own content for "legal" playback. 😊👍

[@tsbrownie]

You must have read my mind, I'm working on that!

[@nonsensicalnonsense4260]

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?

[@tsbrownie]

I can't answer the first question, but for max power each would need an antenna.

[@justtinkering6713]

Now make it FM

[@chuckmaddison2924]

Easy , slope detection.

[@LOVEPREETPAWAR-z5i]

I use this. Type. Of. Variable. Coil. In crystal radio. ..in. 1968. ...working. Very. Well with. OA 79. Germanium. Diode. And. Miltery wireless. Headphone