crystal3.mpg
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- Опубликовано: 29 авг 2024
- In part 3, we discover that our simple crystal set does not work on the medium wave band. All the stations are jumbled together. Improvements need to be made. The first step is to couple in our aerial (antenna) via a variable capacitor. This enables us to get the desired signals better, by avoiding the 'damping effect' caused by the unwanted capacitance of the aerial. Still, results are not totally satisfactory. In order to completely separate the 3 strong nearby radio stations we can receive, we have to isolate the bad effects of the aerial still further, while of course retaining the signals it brings to us! This is achieved by giving the aerial its own completely separate circuit. The signals from this are coupled into our resonant circuit (a 'rejector' circuit) by coupling between the two coils (inductors). And at last we can completely separate the three incoming signals. But there is a price to pay for this: each separate signal is now very weak. Part 4 will attempt to follow in the footsteps of early radio constructors, as they strove to increase the strength of these hard-won separate radio signals.
Thank you for another great class, Dear Professor😊
It's almost as though these lessons were designed for You Tube. You can review each step of each lesson, one at a time. The best learning tool I've ever seen.
Thank you for such a great video. It really nails the tangible improvements from a basic resonance circuit and will be very helpful as I begin my experimentation. Cheers
What I've learned from this, is that selectivity and sensitivity are trade-offs.
Hello Norman, I remember this little project from reading Americana Encyclopedia back when they used to have those printed. Brought a lot of nice memories. Great work old chap.
Thank you. It's been a long time since part 3. Part 4, in which regeneration (or reaction) is introduced, is very long overdue... I'd better get it done soon, before they stop analogue broadcasting in the U.K!
Best regards.
Very good scientific work. Great Video
Yes. On this sort of variable capacitor, the moving vanes are connected to the body of the device. This is the part that goes 'to earth' or ground. The fixed vanes are isolated from the body. So if you check out the diagram on the video at 4min 40 sec, the red wire is the upper one, from the fixed vanes, leading to the diode; and of course, the other, lower wire is the black one which is attached to the body of the capacitor. Hope this helps.
I used the antenna coupling circuit to fix the reception problems of an AM radio in the Cheif's lounge of the ship I was on. They complained that they couldn't get their "country station". All it could get was about half a dozen stations, none country. After I was done, they had stations coming in all up and down the band. The fix was about 4 or 5 turns of wire over the ferrite bar on the back of the set one end to the antenna, the other to ground. The antenna was a 35 foot whip on the outside of the superstructure of the ship. I have no doubts that they were listening to stations even when we were out at sea in the middle of the Pacific.
Hi there. Congratulations - that's a good job you did - there's a great tradition of 'emergency fixes' at sea for radio stuff. OK, today there are mobile phones & satellite stuff, but old-time radio was, for many years, the life-line of seafaring, should an emergency arise. All the best, Norman.
Hi, I am surprised about the very good sound quality of this simple MG receiver!
You could listen with a reasonable volume with a crystal headphone, the only thing you have to do is, put a ,001uF capacitor across the output of the diode and earth. I think that the variable capacitors are 500pF, so if you tune the antenna capacitor in the middle (about 250pF), then use a normal capacitor around 250pF.
On to the next part!
Tanks for sharing.
I always wondered why the early radios had two tuning knobs to get the stations in clearly. Now I know.
Yes, that should work OK. Myabe it will also work if you put the signal into the 'line input' of your sound card - they are usually blue colour. Try line in first. Microphone inputs are usually pink or red. BUT - your computer may be different to mine and something just might go wrong! I hope I don't give you bad advice!
thanks for posting the wonderful video, but I still don't understand your improved coil as far as coupling is concerned
It's quite fitting that you picked up football stations as you sound a little like John Motson! :)
Hee hee, and thanks for the compliment! Well - we're about the same age, which would help, I suppose, although I'm a Brummie & he's from Salford. Thanks anyway! Cheers, Norman.
Try connecting the diode about 25% up from the earthy end of the coil, the improvement in Q is very useful
There was another station at 13:30 for a brief moment in between stations 2 and 3
A question?
I did like you’re video’s over the Kristal radio very very much!
The question is:
On the end of the movie,you use a separate piece of music as an end tune,
Can you tell what song is this?
(I hope to find it back on the internet somewhere?)
Again thank you for the nice video’s,
The beginners learn a lot from it I think!
VrGr Rob.
Hi Rob. Glad you liked the video - and the music at the end. So I just uploaded for you the whole record of that music: the link is ruclips.net/video/qydT1JHJllk/видео.html . I made it sound a bit better. It was recorded in the 1930s. There are other, more modern versions, I think. Best wishes.
Very nice video !!!
I have coils, variable capacitor, diode, but I don't have earpieces of correct type.
I can put the signal in the microphone input of computer card?
Thanks
It’s not a crystal set if you’re using an amplifier it’s just a radio.
Yes, but a demonstration video cannot be made using headphones! 😀
Sorry - reaction should be in part 5. Part 4, with a triode detector/amplifier already exists!
Μπραβο!! Iliked very much your video.May i aski if the diode you used is a 1N34A?IF Not which one then? thank you
Glad you liked the video. The diode used was an old Germanium type called 0A91 - but, the 1N34A is almost exactly the same. It's just a Germanium diode, and in this very simple circuit, I'm sure they would both work equally well. Best wishes to you & yours.
personal question, is your middle initial "H"? and did you own a shop in hurst street Birmingham
Hi there - it was my father who had the shop in Hurst Streeet - I used to work there on Saturdays when I was still at school, so one was surrounded (at least in the mid-1950s) with War Surplus radio gear & stuff like that. Later he went more up-market. I guess you must have used the shop, or perhaps worked there? All the best & thanks for writing. Cheers, Norman.
@@bixanorak as an avid [but novice] HiFi consumer in the late 70's i used the shop to purchase a few items [Pioneer PL512 with a shure m75ed type 2 cartridge - which i still own - though its "retired" to the loft] also, components - but less so. Was so sad to see so any electronics places closing down - though i believe Matthews - is still going - though moved further down the road. Thanks for getting back to me, hope you don't mind me being nosey.
can you show where the wires black and red go on the capacitor, I can't figure that out?
Hello sir great stuff,what about using wave traps !,one or several,that may suck up what you dont want and maybe with the advantage of not loosing volume,i think,,i remmenber years ago in Australia i one day dicided to unwind the coil and i started to get so high that i was able tu tune in shortwave and listen to a few very faint European stations and asian of course, true that a did have a 50 meter antenna in me backyard,i did use those cheap crystal earpieces that are much more sensitive .
First I love your videos, thanks for sharing your wonderful work. I have a question: I want to build a crystal radio that gets 300 hertz range radio waves. A standard coil for a crystal radio is lets say 120 turns. What would I need to do to get the 300 hertz range with a crystal radio? Thanks again for your help.
Still waiting for an answer 5 years later:)
In LW is easy sepparate stations... and LW TRF receivers works with good selectivity...
How far away from transmitters located you crystal set...?
Hi & thanks for writing. Nearly all the stations I received were quite close - three of them came from the same site, only about 30 Km away from my house. That made it easy to receive them! 8^) Best regards, Norman.
GOSTO MITO DO ASSUNTO
O BOM É QUE YOU EXPLICA
OS DETALHES DE COMO MONTAR O APARELHO
can you use a variable capacitor for a trimcap at 10pf or 20pf will it work at like that you think
Que beleza como vcs sáo inteligent muito bom aprendo muito ticher tankuiu abs.
Muito obrigado pela sua mensagem. Isso é muito apreciado; Muito melhores desejos para você e sua família. Boa sorte com Rádio! Normando.
Norman te soy grato que tenhas tomadoum tempo e respodidoisto e muito gratificante pois a sempre o que aprender muitas felicidades e bediçoes a flia gosto e aprecio muito suas postagens.abs
Caro Carlos, É inteiramente do meu prazer ajudar. Meus melhores cumprimentos, Norman.
Nice Vid Norm.
Excuse my noobish question, but what determines the amount turns of wire on the coupling coil?
Thanks for writing! Well - as far as I know - it's not so much the number of turns on the aerial coupling coil, as the fact that the coupling coil is *quite separate* from the main tuning coil. We had 60 turns on the main tuning coil, and maybe 20 on the aerial coupling coil. 15 turns or even 30 turns on it would probably have worked just as well. It's not very critical. One very important thing I forgot to say, is that a capacitor and coil in series - as in our aerial - is an 'Acceptor Circuit'. It allows the desired signal to pass into it, and attenuates others. By contrast, the main tuning circuit is a 'Rejector Circuit', which directs our desired signal to the crystal detector. The action of these two magnetically coupled circuits is therefore complementary, and results in the increased selectivity we obtained. However, as remarked, the final signal is weaker & needs more amplification.
ive made coils with 15, 30, 50, and 100 turns.
the 15 turn coils can receive a couple of SW channels, and sometimes, ham radio!
the 50 and 100 turn coils can receive local stations, but anymore turns, and its the same as the 100-turn coil.
any suggestions?
good video!
Excellent! You have done well to receive short-wave signals on your 15 or 30 turn coils. It's a great challenge to make a short-wave crystal set! The 50- and 100-turn coils are presumably getting medium-wave signals, as you say they are local stations. To get to the long wave, quite obviously, more turns are necessary. But of course, there *may not be any long wave signals* where you are located. AFAIK, long wave broadcasting is confined to Europe. If you live elsewhere, there might simply be nothing there for you to receive! For example, I don't think long waves were ever used in North America. You could try googling for a list of broadcasting stations in your country, and neighbouring ones. I'm just guessing, but long wave broadcast radio probably has a range at night of about 2000 miles - much less in the daytime. So if you are located more than say 1000 miles from a long wave transmitter, there isn't anything for you to pick up. I hope you go on & do more to explore radio reception with home-made gear - it's great fun, isn't it? Good luck! Norman.
i was looking for more power supplies/wall adapters for the wire inside, and found a FM/ MV /9 SW band radio!
ive been listening to cuba, NHK, WHR, and other stations!!
I like your videos, are you a midlander? I am from Walsall, 73's Steve M6PTS
i am trying to make a fm transmitter do you think that will work on that
what is the frequency of this set?
thanks
good job man !
Great video. Where is part 4?
Hi There. Glad you liked the video! Part 4 is at ruclips.net/video/amlJMmwsK8s/видео.html ; Part 5 is at ruclips.net/video/W4fb_qvhz78/видео.html , and Part 6 is at ruclips.net/video/dBz8Kl_mhyY/видео.html ! Hope you like those too. Cheers, Norman.
Thanks. Will check them out too.
thats so nice ! and is there any reason for tuner side to have more turns than antenna side ? like, having more turn at tuner side steps up the signal due to transformer effect ?
Hi there. W-e-e-ll, my knowledge of theory is imperfect - but the bigger, tuning side has to tune the full range of the medium wave, so it has to have an appropriate number of turns, as it did in the previous videos. The smaller (primary) coil magnetically couples the signal from the aerial - sorry, antenna - side. So it *is* a transformer, but it doesn't actually step up the incoming signal, because the primary has less turns than the main (secondary) winding. In fact, it actually reduces the amount of signal into the secondary, but at the same time, increases the selectivity so it's easier to separate the three stations we have here in Birmingham on the Medium Wave. It's a trade-off: we can have very powerful signals, but they're all jumbled up. But by isolating the two circuits, we get better selectivity, though the signal strength is less. But it's pretty easy to amplify these separate signals. I hope this makes sense! Cheers, Norman.
Thanks for the time and explanation. It seemed very logical from selectivity point of view. I am also building a coil to catch radio stations, and I think it will be of great help ! Thanks !
well, i tried this, made a 350uH coil on a 68mm diameter plastic tube with no.25 enamel wire 70turns on secondary and another coil for antenna with ~35 turns about 10mm apart.
now the problem is, our 650KHz station is all over it, it responds very little to 22pf or 220pf (whichever i use) variable capacitor. and even works without the tuner capacitor. i tied connection different taps, only the signal strength is changing. tried a 22pf cap between antenna and antenna coil, but it goes totally silent then.
any suggestions ? i was hoping to listen to some MHz level broadcasts.
Hi there. The traditional value of the tuning capacitor in a crystal set is 500 pF. As you are using a 220 pF variable, that would require a higher inductance - which you have, with 70 turns on a ~2.5" former. So it ought to work. Here, I would use 35 turns on that size former with a 500 pF variable - which is more or less in proportion. So the fact that you only get one station right across the band, probably means that your incoming signal is 'swamping' the tuned circuit. Therefore, you need to reduce the signal from your aerial. This is best done by having another variable capacitor in series with your aerial lead. From what you say, 22 pF is not enough, hence the silence. So it needs more coupling... a variable capacitor will give you this adjustment; though as you mention 220 pF, this might mean you are using one of the the small variable caps that were used in transistor radios & still readily available? The traditional value for use in a crystal set was 500 pF - if you could get one of those, it would be best to use that with 35 turns on your secondary, and say 15 turns on your primary, and use the 200 pF you already have as the aerial coupling cap. into the primary. Hope this may be of help. Cheers, Norman.
hello, you mean the primary coil inductance is probably too high (125uH) for faint signals to pass ? will it be better if i make that 15turn coil as you suggested with 1mm (no.19) enamel wire (23uH) ? or just that 0.5mm (no.25) enamel wire should be ok ?
i use those commercial AM(220pf) / FM(22-30pf) radio tuner caps that i have for some time now, i guess some shops still have some old stock of those FM tuners. but getting a variable cap like yours could be problem, i don't think i have seen them in shops, even if there are those, they will be pretty expensive.
i will try later with a transistor to amplify the signal, but that may take few days or couple of weeks. meanwhile feeding it directly to an lm386, because i have no high impedance headset.