Popular Crystal Radio Design That's a Waste of Time - And Why (Updated Video Available)
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- Опубликовано: 21 окт 2024
- This design can be found all over the internet, but it does not work any better than a diode and an earphone hooked to an antenna. We compare this common design to the modified Boy Scout version. And my opinion on why this popular design does not work well.
There's a comparison of circuit diagrams at the end of the video.
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About 50 years ago, I made my own crystal radio and it worked great. A rock collection that I had that was stuck to a sheet of cardboard, also included one quartz rock, and so that one particular rock became my crystal detector. Either sliding the coil bar, or changing the position of the "cat whisker" wire that was probing the quartz crystal, could be used to select channels. The layout I used is the same as what is shown at "Crystal radio - Wikipedia" in the Basic Principles section. See the Pictorial diagram from 1922 showing the circuit of a crystal radio.
Some of you are missing the other half of the equasion. Antenna. We ham operators had longwire antennas, dipole antennas. Loading coils for imedance matching. You need a signal to come in and tune to its frequency. Disconnect your antenna from your receiver, you get nothing.
I agree with you on the first premise. The first design does not work for most of us and that discourages many newcomers and young followers.
The reason I can say are three main factors. Antenna coupling, antenna capacitance and Q factor.
The second design works best because it is an variable transformer. It has high variance on the capacitance of the circuit. That design of coil includes an unwanted capacitance that's makes a runner circuit tank. It has better Q.
The first design is for a short and high impedance antenna already tuned to the broadcast band. It is just bad if you use a random piece of wire and feed that on top of the 'hot' side of the coil.
Your random length wire will have a lot of capacitance on it and it will add to your variable tuning capacitor and you don't see it. Remove your running capacitor and you may hear an increase in volume. Instead of that big variable capacitor 20-360 pF try 5-50pF. Or use another variable capacitor between your coil and your antenna wire to 'trim' the length of your antenna and reduce the extra capacitance you are introducing into the circuit.
As many other said and did the antenna must be coupled with a tap between 10% and 30% of the coil. Also the use of a separate coil for running the antenna will get you better results. Look for 'antenna tuner variometer' like in the old days.
Yes you are correct of course, and I'm sure your change of capacitance would help. What I am trying to do is accurately re-create what is probably the most popular design you can find on the internet, and then show it does not work. Even with "reasonable" changes such as varying coil it does not work. Hopefully people will see the video and go for a workable design.
I get sort of where youre coming from with this. The tapped concept can be infinitely better, however, with several additional modifications. I can agree with you though that exclusively tuning with the air capacitor is not going to get you the range you want. Tapping the coil in multiple locations AND using it is going to get you better selectivity than your slider radio though, if designed properly. It would effectively allow you to be able to select half-way-around points on your coil where the slider can only reach single rungs (if that makes any sense).Also you have to consider that if your coil does not change ... that there is basically one set resonance attainable by your circuit with that capacitor. Youre basically tuning it in closer to the one spot it really resonates at in that config. You touched on it with your explanation of the slider model. You are effectively changing both (and in effect moving across several different resonating combinations) when you slide. You have the beginnings though of a better model ... its just more complicated to get your bang for buck.
I've got the parts to do what you are talking about, just need to find time to work on it.
Check your coil in your first radio. Its a large diameter and higher inductance. You can find solenoid inductance formulas all over the internet. Diameter makes a difference. It looks like your problem is you could have tuned yourself out of the broadcast band. It should measure about 200 uh with an LCR meter. You can get an LCR meter cheap on ebay. a 365 pf variable cap will tune the broadcast band. For ground use a 6' ground rod or galvanized cold water pipe and keep the ground lead in as short as possible. If you are in a metropolitan area with many strong stations a wire antenna of 50 feet should work fine. Don't use coax. The input impedance is very high on the antenna circuit of a crystal set. 50 ohm coax will short it out. Use a 1n34 germanium diode. Notice your coil on your boy scout radio is much smaller and lower inductance then the left side big coil radio. BS coil looks about right. The basic crystal design will receive a lot of stations. I had one as a kid and it worked great. I was using a galena crystal. My 50' antenna worked great. I extended it to another tree in my yard to about 100 feet and it didn't work as well. I never figured out why. I think I must have grounded it somehow. I think 50 feet resonated well. Its very fun to experiment with different crystal circuits.
For better information from the internet on how to do things, I find that going to overseas websites, UK, etc. where there is still a viable educational system on technical matters, is usually better. The US sites are full of misinformation that gets copied and recopied. (As a fellow US citizen, it's embarrassing, but true.)
Better to have the diode and earphone tapped about a quarter of the way down the coil(not swamping out the high impedance of the coil/capacitor tuned circuit).A small capacitor(around 100-1000pf)across the earphone helps in detection,too(filters out rf after detection).
Great job. You are 100 % right i gave up on buidling a crystal radio years ago based on that flawed design. But now i am inspired..
Thanks.
I'm glad to hear that. Let us know how it goes.
Are you quite sure you want in the second diagram, the ground at the top and not the bottom? Consider when you have maximum inductance for lower freq stations ( the slider arm more towards bottom of diagram. ) In that case, the diode circuit is across a smaller part of this autotransformer, and the output voltage is less than over the whole coil.
It's a good question. I did try putting the ground (and antenna) on every intersection to see if that would help. Nope. I'm still trying to make it work. Part of the problem is that it is very sensitive and therefore good at discriminating among signals, BUT (and it's a big but) anything you attach to the circuit that is anything but extremely high impedance kills the resonance (I've been using an oscilloscope on it). I know it must work! Will keep beating my head on this wall until I figure it out or I die in the effort! ;)
Great video, with the first model with the air variable, makes sense why it isn't favored, not much capacitance to work with.
Just 80 turns does not determine the inductance. It is dependant on diameter and turn spacing as well
ala Robert Turner : 80 turns 26awg wire yields a coli of 1.27 length :
1.27/80 = 0.158in/turn close wound
Curious if you've tried a highbryd design, i.e. instead of locking the variable cap in at 80 turns, hook up the whiper as in the modified boy scout system, then hook the variable cap to the wiper? Perhaps the cap may serve to fine tune the channel.
Interesting idea. I will have to ponder the values on the cap and such.
I am way out of practice with electronics, haven't worked in the field for 20 years now, and definitely no real RF experience, so I might be overlooking something. But the general concept seems plausible. Really enjoyed your video. Would love to see the results if a hybrid works out for you.
If you disconnect the ground your signal strength will go down, but most likely your selectivity with your variable capacitor/coil set will go up. You can also hook up another variable capacitor in series with the ground wire and use minimum capacitance setting and find a balance of volume and selectivity. Crystal phones are OK(as long as they don't drop out on you) but sound powered phones with matching transformer would open up a whole new world in sensitivity and reliability. You can't tune into what you can't hear. SP phones were the best bang for the buck modification for my crystal sets.
Couldn't concur more. At 8 or 9 years-old, ran 18g Xformer wire from bedroom window to house peak to telephone pole and onto a tree in a 6-acre open lot behind home. Must have been 50 to 60yds long and 25' above terra fima. Drove a 12'' galvanized pipe into the ground and ran lines into my room. Used an old HeathKit speaker box (the one with copper springs for quick attach-detach) placing a 1n4148, or facsimile, between the contact leads with ANT and GND affixed across the diode. Given a 3'' paper-cone speaker (5+ decade old technology), radio broadcasts still could be heard clearly in several rooms. Closest AM beacon, w/largest US footprint, was ~5mi. away. During daylight hours, it swamped other local AM-stations. At night could hear faint remnants of other stations, as nearest broadcast overwhelmed all others. Only when local beacon was shutdown for periodic overnight maintenance could one observe other stations (15-50mi. off, LOS). During rare maintenance windows when skips were profound, one could receive signals from NYC, CIN, INDY or DNVR, of course none of them without significant interference from other stations but still identifiable between competing dialogues. Would have been interesting to have a two or three stage tunable front end filter (Hi-Q) to see how well the local station could be suppressed and see what selectivity could yield other distinct broadcasts.
That was interesting you could get that much volume out of a low impedance device (8 ohms?). Did you add a way to tune it?
@@tsbrownie Nah, moved onto what most 8/9 year-olds did; fixing household gadgets, like modern day ALASKAN reality shows build new homesteads--we christened a new fort each sp/su, baseball-basketball-hockey, taunted girls, pushed-and-peeled, kept up on studies, forged wild berries and engaged in general 60's suburban mischief with the throngs of likeminded kids. Back then, HAMs were utter outcasts: last picked on teams, glasses, pocket protectors, goofy, socially awkward, disheveled, some very bright--others dimly lit. Radio alone wasn't enough common ground for me to overcome my insecurities. Alas, on the strength of my math/science skills I pursued that nascent interest in Rf-Comm and Sys Eng for 2 decades beyond university. Thanks for your postings and will continue checking for updates. Best.
I don't mean to get too "Electrical Theory" on you but ... if you apply the equation for resonance to your circuit there you will have an Aha! moment as to why that specific build should only work for one or two stations. The capacitor is only allowing you to dial into that resonance at its peak so you can get the best sound quality for that one 80turn coil. In the slider model you can only hope that the passive capacitance and inductance both match up where it happens to be laying (then you get a station, at resonance), you cant tune either L or C independently in a slider though. The air cap just keeps you from needing a much larger device to get the same selectivity, like say out of a single coil only type radio. You oughta try putting that air cap on your slider model and see if you think its an improvement then ...
I've run the numbers for the coils and caps from some online sites and theoretically they cover the AM band. In practice things like antenna (length, orientation), proximity to ground planes (like when I showed on on the AC unit), my body positioning (seriously), nearby electrical devices (our plasma tv really interferes badly), etc. all affect the actual outcome. In fact many times the electricity involved behaves more like static electricity than regular. I've got computer USB scope on order so I can finally see what is really going on! Can't wait!
Yes, that interference is what you would expect if you could not narrow your peak for resonance, to make the station youre tuning into the strongest one coming through. The thing is most coils (if not all, I'm not sure what the perfect dimensions would be ... that's a fun math problem to tackle ... it would probably involve some sort of Rodan-esque increasing geometric iteration coil to make the tuning linear ... or simply one of those air capacitors that taper but whose slope would match up with the coil you've built ...), but most are not going to adjust Henrys vs. Farads in a fashion that keeps their graphs aligned ... and therefore makes them perfectly tuned as you slide. You can calculate it yourself by running what would be your slider point of the coil at different points. Youll see its not a linear relationship already. The internal capacitance of the coil is not either. Hence why if you can decouple these elements of the radio (capacitance and inductance in your tank circuit) and adjust them independently you can achieve better performance.
There are too many parameters missing in most of the versions of this particular radio that you'll find. With a 365pF varicap the coil should come close to 240uH. using 26 awg magnet wire and a 1.75" toilet roll tube 80 turns will cover about 1.27" and give approx. 237uH or so. Try winding a coil to those specs and plugging it in. You should be able to tune the AM Broadcast Band then.
90 turns of 24 awg will provide a higher Q coil of about 240uH on a 1.75" form.
+Robert Turner 244uH I meant. ..
+Robert Turner I agree, many versions have some parameters missing. The radio "works", it just picks up 1 or 2 stations. I have demonstrated that with just a diode and earphone. The point I was trying to make is that the capacitor and coil don't really do anything in this version. My thought was that with the wiper style the induction and capacitance (in the coil) vary a lot and in lock step, unlike the variable capacitor with fixed coil (inductor). I need to do some more experimentation.
+tsbrownie I actually used a 240uH choke (this particular one looked like a half watt resistor) and a varicap of 0-410pF. It worked pretty good but needed a good Antenna and ground, but it was cool because it was just the cap with the choke and diode soldered to it. I just clipped on the antenna and ground and an old high impedance magnetic earphone to use it.
That does sound cool! I think my older brother had something like that once, but the memory is hazy. I think I may have those parts in my parts bin, will see if I can find them and make it happen. I don't have the high impedance magnetic earphone but where there's a will, there's a way (and usually where there's a will there are relatives coming out of the woodwork! ;)
perhaps something is missing or lost over the course of time fom the original design;
ike a ferrite rod sliding partially in and out of the coil along witj the antenna wire to tune it
Sounds like you are describing the "rocket radios" (I had one of those when I was a kid). It's a different circuit design for a crystal radio. There are dozens and dozens of crystal radio designs, some are better than others.
when i was a kid i used to disassemble electronic stuff like radios, and i think there's always a black tube in the antenna part that seems to be a magnet.
what's the difference between that and the pvc pipe? is the magnet stuff only useful for powered radios?
There's what they call ferro-magnetic bars, toroid and such. It's not really magnetic like we think about magnets, it only magnetizes for really, really short time periods and only when there's a change in current in the surrounding wire. Like the core of a transformer, but even less permanent.
It's not a magnet, just looks like one. And, it will stick to a magnet. It's powdered iron oxides in a binder. The reason for it is that solid iron would have lousy frequency response, while the particulates work quite well at higher frequencies. It could be used in either a powered radio or a crystal set. The purpose of it is to increase the permeability of the core of a coil and increases its inductance.
To make first coil work better try shorter antenna, say 12 feet. Mess with disconnected ground or ground to your skin. Coil is too long at that diameter, try tapping midway from 0-80 and in tap remaining taps.
Crystal Radio is addicting!
I keep promising to make an antenna tuner, which you know means I don't have to change antenna length. I'm lazy, so that's my first choice. Yes, it is addictive and fun.
Hello brownie
Hope u r well
I've been experimenting
I have a 283 uH diamond litz coil and capacitor is 30 to 320 pf
If I loop feed coil i.e. aerial and ground go to a 10 turn of 3 in diamter wire and place next to coil
My receiver works exactly as it should
530 to 1700 khz as per lc formula
But signals are weak
If I go by the old basic standard like you started with and connect aerial directly to coil , capacitor which then goes to diode stations are booming but the capacitance from aerial Lowers my frequency now tunes 400 khz to 1300 khz ....but I tried this, I connected aerial to one leg of coil and the other leg went to capacitor which goes to diode, my frequency raised about 150 khz
Now tunes 650 to 1800 khz
But the stations are stronger than with the simple loop coupling and very very sharp tuning better than loop even though stations are stronger and the audio sounds fine
While at sea I connected antenna directly to coil which goes to cap which goes to diode and the other leg of coil of course goes to cap which goes to ground. That's the strongest and of course 70 mile out didn't have trouble with saturation but signals were broad
I've got goodys coming in on Tuesday.
I'm curious to try loop coupling using variable capacitors to tune aerial and a coil not just a roll of wire
You should post some videos on youtube so we can see what you are doing. Would be interesting.
@@tsbrownie I'll be home in 2 months....
Philippines
When I get antenna radio setup I'll make RUclips video
@@uncleruckus4060 Please post the link here. Can't wait to see it!
Did you try a transformer type coil to step up voltage and isolate antenna and primary winding to increase selectivity in the secondary tuned circuit...i think a one coil system is not very selective...from what i have read...?????
+John Baart I have tried various antenna tuning circuits, but have not been rigorous in testing. Some seemed to make the signal a lot sharper, others made it louder. Did not find where I could get more stations / discrimination. Will have to get serious and find out one way or the other. Thanks for the info.
Try adding an extra tuning capacitor to the coil
The intrinsic capacitance(too high) of the coil and the antenna across the coil as probably knocked the tuning range low - away from what it would be calculated as. Damping the resonance as well at the same time - is that what you mean?
I tried every tap on that coil, 10 turns, 20, 30, 50, 70, 90, 110, 130, 150. I also tried (not in the video) some much smaller mica caps and bigger caps and nothing. I could get it to tune a couple of stations at best. I doubt the coil capacitance is overwhelming the circuit because I am now using that same coil in another radio (modified, modified boy scout) and it works fine (video coming out one of these days). But the antenna could be an issue. Maybe if it was coupled instead of direct... May have to revisit that. Thanks for the kick in the complacency. I need those now and again!
Hi tsb - I've built a few. 50 turns on a ferrite rod and 365pF VC I could separate about 4 stations in the day. So there was some resonance going on. But there's no tuning at all with your 1st one.Something's damping the circuit. The reactance (Xc) through the diode and earpiece if low at RF isn't going to help. Also coax feed from a wire outside if the screen is connected to ground will cause loss.Your tuning cap looks about 100pF BTW?Because you're tapping into the coil the redundant windings creating an auto transformer - Some kind of destructive phase thing - could be a dielectric loss (the coil will have an electric field as well) to the former. Not as likely though LOL!
@@tonystephen6312 I have to try one with a ferrite rod. The cap I used is 365pF. The antenna wire is not really coax, it's a broken down coax, and I used just the outer shield for the antenna. The ground was to the house's steel. There are many other designs that work so much better than the one being tested. The boy scout radio will pick up 17 stations and it can be built from mostly scrap stuff around the house.
The boy scout radio sounds good - with the sliding bar tuning. It kind of looks like it tunes 2 sections of band at the same time though, which is confusing?!
@@tonystephen6312 I don't understand what you mean by "2 sections of the band".
What is the value of that variable cap.? It sure doesn't look like 365mmf. I don't believe it has enough variation of capacitance to change the value of L/C network to tune across the band. When I was a kid, a made many crystal radios with that circuit. Wound the coil on a toilet paper tube, and used 365mmf variables from old radios. They worked loud and clear. with fewer windings on the coil, I even picket up Radio Moscow (if was on the east coast).
It's 356 pFs for sure. That's the value that all these designs call for (you can google for a while and find this same circuit diagram again and again. I think it's people copying it). As I said in the video, I can get 1-2 stations and they are pretty strong, BUT with the others I can get up to 17 stations. I can get 1 station just using a germanium diode, so why bother with the coil and cap? I've got another design that works really well. Excellent discrimination, but not quite as loud. ruclips.net/video/AaNpFYe5dSo/видео.html
Which capacitance on the rightside design? there is only inductor
The coil and earphone both have capacitance.
@@tsbrownie but the coil works as inductor. how come it has capacitance? and if it does, shouldnt it be neglectable?
@@jm10oct Everything has capacitance, inductance and resistance / reactance. In this case, the coil has enough capacitance to meet the need. Oh, and the new piezoelectric earphones have capacitance too, hence the elimination of the cap that was used in radios from 50 years ago which used the original crystal earphones.
What antenna design are you using?
Straight wire.
If you tune the capacitor of a parallel resonant circuit, you should hear a peak and a drop in the signal, even if there is only a single station. Your tapped coil and capacitor does not sound like it is doing this.
I think the reason why is because the tapped coil has too much inductance and the resonant frequency iss much too low, well below the broadcast band. The typical crystal set uses a 365 pF variable capacitor and a coil that is about 180 to 220 microhenrys. I think that your coil is much more, it's a very large coil. The coils that I've measured are about 1.25 inch or 30 mm diameter and 2 or 3 inches or 50 to 60 mm long.
I think you should be using the tap that is 40 turns or even less, 20 turns. You may have to go even less, by using a smaller sized coil. Thanks for the video.
I think you are right. I have tried many coils, bigger, much bigger, smaller and tiny, but it's never very good. I need to spend some more time on it.
I had one of those "boy scout" radios back in the 50's/60's. It only got two stations at best. Mine however had the coil between the antenna and ground with the tap going to the detector then ground. I like your mod, at first I thought it was crazy, but the more I looked at it, yeh....crazy like a fox. It gives a better antenna match.
I grew up in a small Midwest town and even with a really good antenna also had limited reception. If you are near a big city with lots of AM stations you can get a lot more stations. As a bit of trivia, the boy scout design in my wolf scout book (I've still got it) had an error in the picture, it had an extra wire that was shorting the coil if I recall. I still remembered that decades later when I built this one. Glad you liked it. The capacitor one I did also works very well. Most of the designs you find for capacitive tuned ones don't work at all like the one in this video.
Great video, I very much back up everything you are saying, why dose the internet place these circuit ideas out there that do not work I have no idea.
The wire across the coil works well instead of a mechanical variable capacitor.
thank you, ive tried the popular schematic and failed myself..what youre saying makes sense..
What difference between one coil scheme and double coil design with link coil ?
If I understand, the second coil is often to match the impedance of the radio with the impedance of the antenna.
I used a free Google Play app called ElectroDroid to do some calculations. A coil with 80 turns and roughly the same diameter and length as yours has an inductance of about 400 microhenrys. It resonates with a 365 pF capacitor at about 400 kHz, which is well below the AM broadcast band.
It looks to me like the coil needs a lot less turns. If you have an Android phone you can download this app or use a different one for Windows or whatever. It makes getting a ballpark estimate so much easier.
L8r...
I downloaded that a while back and have not played with it much. Yes, the coil is much bigger than the one on the wiper-style radio, but I have taps every 20 turns so I can try many different inductances. It just never got more than 2 stations. I think it has to do with being able to vary BOTH capacitance and inductance over a very large range: the capacitance of the wiper style is coming from the coil and when one varies the inductance you are also varying the capacitance in direct proportion. Theoretically one could do that with independent coils and capacitors, but I've not given that a fair trial yet. It's on my long (and every growing) list of things to do!
My guess is that the variable capacitor is the wrong type for this coil. Also the coil itself doesn't have enough turns so the frequency range is too narrow. I usually go with about 120 turns and use a cheap variable capacitor and have gotten good results.
These coils have 170+ turns. I have been experimenting with different coils, from very tiny to mid to large like this one. The cap used is the "magic" 365 pF that the most popular design calls for, and that's what this video is about, debunking a design that is all over the internet. This was built to the most popular specs. If you look at a modern transistor radio the coils used with the 365 (or thereabouts) cap are small and multiple, so obviously it works. But that's also in conjunction with a ferrite core of significant henries. The quest goes on for a sensitive crystal receiver with good channel separation.
You are missing a seperate induction coil on the first kit.
That may be the problem. The diagram I show is all over the internet claiming it works and it does not. If it needs other components to function, they don't mention them!
I have the worlds most powerful am/sw station less then 10 miles away so only one station for me period
You might be able to use your house or other buildings to shield their signal. Just a thought.
Mine receives 560 kHz and this one is strong, a weaker Mexican station around 900 kHz and one cb on 27 Mhz that seems to be located nearby at the same time. For my first radio, this is AWESOME!! I have built 2 others that suck too (especially the one using a microwave power transformer secondary coil that only looks cool) BUT and that's a big but, I want to build a better one I can permanently leave in the hunting shack all the time and have tunes. especially that some wandering bastard doesn't go and take! Or at least I can easily make a replacement. Wind a secondary coil with an inductance from 136 to 141 uH. Subtract turns one at a time till you get your favorite station coming in strongest.
This one works well, but it's a bit complex:
ruclips.net/video/AaNpFYe5dSo/видео.html
This one is very simple, but tuning is less precise:
ruclips.net/video/8XR9Uzy2RPM/видео.html
well maybe if you take it out side to get best reception remember they transmit 10000 watts or what ever and you have to get best location see this thing is a radiant energy collection device and it picks up allot of signals if the electric was out and you had a more calm environment it probably work better but see what it really is a way to collect electric from the environment for free and this is why we don't really see it much anymore wouldn't want people to get the idea to stick up an antenna to collect free energy. IE easy to get energy.
Well that is odd. 51 years ago, I built my own crystal radio. The crystal, or diode, was an actual small rock of quartz crystal which was placed within aluminum foil with a wire poking at the exposed area. The other wire was wrapped around the cardboard of toilet paper. The ear piece was part of an old landline telephone. It worked perfectly. Anyhow, I ended up with two different ways of picking up a channel. I could change the pickup point on the wire coil, or I could change the poking point on the quartz crystal rock.
I have never heard of using quartz, I will have to look into that. I have used galena crystals that worked as you described.
In a sense, the one on the Right, has a Second IF stage.
gee maybe there are only a couple stations in your area???
As I mentioned, I've picked up 17 on one of the other rigs. This does plain not work. I've got another capacitor design that works well.
Based on the comments, almost no one realizes that they don't understand anything.
View the Microwave1 series of videos on crystal radios. He has done a great job. His radios pick up many stations and operate very clearly. His most recent uses a varicap diode instead of the variable capacitor and works very well.
Billy Cheung is the master of that style of radio, he has some that require no battery. And is it really a "crystal radio" if it needs a battery?
ruclips.net/video/5bBwmOQHVzM/видео.html
Also I noticed that some of the advice that microwave1 gives is sub-optimal for average users, for example he has a cap across the output which works for the old earphones he is using, or the amplifier, but for the new piezoelectric earphones it causes problems. Perhaps I'm too much of a purist but the easier workaround to a cap (which costs more and is less sensitive), is the slider/wiper style which avoids the costs, "unobtainium", and batteries of caps or varactors.
I had a rocket radio which used a ferrite core transformer and and adjusting the ferrite core worked good to change channels,,,with two leads for antenna and ground-- 3 feet long each with alligator clips...coil was like the size of a pencil with movable core rod inside....hooked antenna near light and ground to iron bedrail and was good....never tried on a longwire antenna...maybe a lot better...
+John Baart I did also,attached the antenna clip to the telephone base.I picked up CBC radio very well.Nice little radio for it's day.
+Michael Henwood Yeah, back when AM radio was all we had and the stations were mostly rock and roll....not junk like they broadcast now on AM......
I've built foxhole radios that had a razor blade instead of a diode that would work you must Be doing something wrong we did use an antenna that was a very important part of getting AM reception and there prolly were more AM stations back then in 1958? Lol foxhole radios got the name during WW1 so soldiers in the trenches could hear what was going on in the outside world no diodes available in foxholes back then but a single edged razor blade with a whisker and a long antenna could pull in AM signals enameled wire was used a lot back then did you sand the enamel off the coil where the whisker would run??
I think you are right, there are fewer AM stations today, some have converted to digital which won't work with this radio. Yes, you have to sand the enamel off on the places where there are connections and where the wiper runs or it won't work.
It is true that it is not one of the best but in my case made me want it to be better and then I was hooked.
I think the problem is somewhere else than you think. It's not that there is anything wrong with a capacitor-tuned circuit, it just doesn't work correctly when it doesn't have the right conditions. Unsuitable conditions are, for example, direct coupling of the antenna, which detunes the circuit, and direct coupling of the detector, which loads it. The solution is right in front of your eyes, you just ignore it and look for substitute reasons and problems elsewhere.
You can watch this video where I finally found a 1 capacitor design that works.
ruclips.net/video/0AvTO588SyU/видео.html
But the common design you find all over the internet does not. There are many websites debunking that design.
There's also a 2 capacitor version that works here:
ruclips.net/video/0AvTO588SyU/видео.html
Or you can build the design that does not work and show me where I'm wrong. I don't mind learning.
Hi, since I was 10.... I've experimented with so many..... my 1rst was from Morgans book... it was the one with a slider... I t worked good... Then I experimented many others... they sucked ... did the same like you did...my favorite is the Loop crystal radio.. I've seen some where they can get shortwave...
+Paul Pedrazza My first 2 were from the boy scout handbook, with a couple of changes. My second was a copy of a "rocket radio". I have not tried a loop, it sounds like you would recommend it, so I will have to give that a try! Thanks.
+tsbrownie
I would recommend a loop also. It can be as simple as constructing a octagonal(or any other shape) frame of wood and stretching around 4-6 turns of 18 gage wire over it and attaching a 365 pf variable and your phones/diode. No need for an external antenna or ground and the set will be direction. It's a bit large, but works well.
very true
who size diod
Not size. Type = 1N34A. MUST be this!
+tsbrownie thank you. Iam don English Iam Iraq
Good luck and have fun!
A antenna coupling helps alot kg6mn
True. Also tuning the antenna helps. I should do a video on that.
Sawasdee krub, it sounds like a station in Thailand!