Crystal Radio--Using SMD Inductors??? (4K)

[@tsbrownie]

OK, OK, SMD inductors are NOT solid state, it's a bad habit.

[@Pygar2]

Love to see you place a ferrite rod across them!

[@tsbrownie]

@Pygar2 I tried and it did nothing, which surprised me. I think the EM field in these inductors is well contained.

[@Pygar2]

@@tsbrownie ... which explains why lining them up didn't work! Thanks, though!

[@ehsnils]

A crystal receiver is a solid state device. 😉 My concern here is the Q factor being low so the receiver will become inefficient (bad sensitivity and selectivity).

[@tsbrownie]

@@ehsnils I think that is the biggest part of the problem.

[@haraldlonn898]

There is not much magnetic coupling between the different smd coils. Only matching the impedance will not make it work. Hope I could explain it good enough.

[@jagmarc]

Aren't they supposed to be mutually coupled with eachother?

[@tsbrownie]

@@jagmarc Yes. I think these inductors contain most of the EM field, so that's a problem.

[@gg630504]

A tapped coil is an autotransformer. Replacing a transformer with inductors is like replacing a BC182 with two 1N4148s.

[@aaronwoodard3354]

Neat experiment. Perhaps the coil orientations might be interfering with each other. Try it with the inductors stacked on top of each other, or each one separated by a larger distance. In the past I've used the green axial inductors (end to end) with decent results. Don't give up!

[@tsbrownie]

@@aaronwoodard3354 Thanks. I had not thought about orientation. I will have to look into that.

[@migalito1955]

@@aaronwoodard3354 Excellent idea. This determination ought to be interesting. I still can't help but think the idea must be more viable than the initial test indicated.

[@franzliszt3195]

yes, stacking, but make sure the B field all goes in the same direction. If one of them gets reversed, then you may get nothing at all.

[@fredfred2363]

How are the SMD coils wound? Don't they all need to pass the "magnetism" all through each other?

[@karltrepka1627]

maybe the sizing of yr smd inductors didn't allow for mutual inductance?...ie these are "separated coils'.....coupling these inductors could be done with a variable capacitor?...maybe between the antenna coil and the main tuner coil?

[@fiskurtjorn]

0:38 Don't the big coils are in line, sharing the "core". And do the SMD ones have their cores vertically, next to each other? And is this affecting their influence on each other?

[@tsbrownie]

This type of inductor that I have broken open in the past have the coil horizontal. But this may be different.

[@cdorcey1735]

I suggest using a different radio circuit. The usual radio circuit using coupled inductors for impedance matching, but there's an analogous circuit that uses a capacitor network with a single inductor. In fact, I have it working on my desk right now! Instead of tapping the inductor side of the LC resonator, tap the capacitor side. That is, put two capacitors in series, those parallel with the inductor. I'm using 150 pF between the antenna input and ground, with a 10-400 pF variable capacitor between input and the top of the inductor. My inductor is 40T on a 3" cardboard form (salt box). My diode comes right off the top of the inductor. Since this design uses only a single inductor (200 uH, if I've calculated in right), you should be able to use an SMD inductor in its place. (PS: My antenna is a dipole cut for 3.5 MHz, 50-ohm impedance, my earpiece

[@tsbrownie]

I think your comment got cut off.

[@cdorcey1735]

@@tsbrownie You're right. The last sentence should have read "my earpiece is a high-Z crystal earpiece from a commercial crystal radio kit." If you want more details on the "single-inductor, capacitor coupled", design, I could send an email if I had your address. I'm at "lathechuck (as shown in my photo)", using a popular email service (if you care to guess).

[@tsbrownie]

@cdorcey1735 My email is in the "about" on my channel. I'm always interested in new designs. Thanks.

[@Lechoslowianin]

Hello. Maybe the winding directions are not the same

[@tsbrownie]

@@Lechoslowianin Interesting. I will check.

[@Slickdealer]

Fundamental problem here is assuming inductance is linear with number of turns. Inductance goes with the square of turns because of coupling.

[@paulperry7091]

Yes, but the fundamental problem is that you can't split the coil into three separate individual ones. As others say, the sections must be inductively coupled.

[@sebastian19745]

@@paulperry7091 Yes, you can (in theory), that is how modeling an equivalent circuit works. But I am not sure about how it works if the equivalent circuit is built, I never tought at that. Maybe some experiments?

[@tsbrownie]

I may have an issue of coupling because I assumed the coil was horizontal (like some smaller, rectangular ones I broke open), but if these are vertically oriented, that could be a huge issue. I need to break one of these open and see.

[@davidfalconer8913]

A HUGE coil on a scrap ( card toilet roll 😝) will always work best , the ( Q ) is MUCH higher .... the UK ( Mullard ™ ) Germanium diode , type OA79 has been found to be the most efficient for such tiny RF voltages , but the OA81 is almost as good .. the old 1960's ( pink ! ) crystal earpieces also help a MUCH louder reception ..... DAVE™🛑

[@jagmarc]

Seeing lumped value components used together to form a tuned circuit, inspires me to suggest take the idea further by... Having a PI network, to do an impedance transformer, by using two independent variable caps. Tune in by finding the best contribution from each the two caps to resonate with the coil. Similar to having twin wipers on a coil but in reverse. Of course the coil needs to be instead a decent Q , biggish diameter, maybe litz wire or a ferrite. But not these SMD broadband low Q thing.

[@tsbrownie]

Interesting. I was surprised how low the Q value is on these. Should have looked before I leaped, but then that takes all the fun out of it! ;)

[@jagmarc]

@tsbrownie a bit further explaining on the PI network idea, two grounded variable caps, their fixed plates attached either side of a fixed inductor. It makes a versatile resonant impedance transformer. It's often used in an ATU box, with two knobs to match a transmitter with a complex impedance.

[@jagmarc]

@tsbrownie Low Q is sometimes a good thing, stops ringing after a pulse.

[@stewartbaker2752]

Two things :- The "Q" of the SMD inductors, and very little self coupling between them. Surprised you received anything...

[@jozefbubez6116]

Yeah! If you look at the data sheets for SMD inductors, the 'Q' is quite low compared to their bigger counterparts. For a good crystal-radio, you need the highest 'Q' you can get.

[@kokodin5895]

i would assume the coils in those inductors are all measuring the same inductance as the package says but what is the polarity? if a coil is stuck inside with vertical core then your colective inductor looks nothing like single coil with multiple taps . It might have the same inductance but in that orientation side by side coils could magnetically interfere with each other rather than adds up what would happen if you stack them up with all cores facing the same direction only one on top of each other? assuming they all align magnetically

[@tsbrownie]

@kokodin5895 Good questions. The coils of this type I have broken apart in the past were horizontally oriented, but that does not guarantee these are. It's very likely they are wound the same direction because they came out of an auto-placement strip.

[@mnoxman]

Even 1900's "crystal" radios didn't have any vacuum state. I think that the tungsten on quartz "cats whisker" diode of old could be classified as solid state.

[@tsbrownie]

@@mnoxman I like to think so.

[@_a.z]

The inductors aren't coupled

[@spvillano]

They're also very low Q value and most are rated at their Q values for much higher frequencies. One can get by with lower Q values if regeneration is used, but coupling such in an SMD inductor is beyond problematic outside of a factory. In theory, it could be done, but we're talking sealed units with silver wire and frankly, absurd pricing due to what's involved in such a super niche application. Interesting head melter, I'll put it on one of my back burner project lists.

[@johnharris6589]

I think the wound and tapped coil acts as an auto transformer as well as a string of inductors try placing a piece of transformer steel or ferrite rod where your finger was and it might improve. I think some inductors are designed for minimum external magnetic fields which would not help.

[@tsbrownie]

@johnharris6589 I tried a ferrite rod on the inductors and it did nothing. I afree these inductors probably contain the EM field.

[@franzliszt3195]

If there is core material, what frequency range is it for?

[@tsbrownie]

@franzliszt3195 The place I bought it from dies not say. I hokked it to my oscilloscope and frequency generator and it passes the AM band easily.

[@AtomkeySinclair]

Maybe a super tiny coil instead?

[@tsbrownie]

@AtomkeySinclair Smaller coils are less efficient. It seems there is a size below which it will only tune 1 or 2 stations, but I can't find any historical info, so I am experimenting.

[@perttisalonen850]

Use more flux to the soldering points of SMD inductors. You can't use too much flux for soldering of SMD parts!

[@deletemeforevs]

Like the circuit would be same full circuit but take the coil off and jumper those connections. I bet you will hear that station or 2. :)

[@tsbrownie]

@maikerumine I have a video on just using a diode only. This is only a little better and costs a LOT more.

[@migalito1955]

Cool beans. I just started the video. I expect it to work..... Ok, saw the entire video & it was interesting. Looking forward to where this leads to. Disregard the following, I found it in your video library. I Like your scope. I Tried to zoom in & see a brand name but to no avail. If you could indicate its brand I'd appreciate it. Also, can you indicate max frequency.

[@tsbrownie]

DIGITAL OSCILLOSCOPE DSO3D12 Designed by ZEEWEII

[@deletemeforevs]

What you were tuning was antenna. Do same experiment without the smd and use a short.

[@tsbrownie]

@@deletemeforevs You mean just use a diode? If so, I have done that. It works almost as well as this. 😞

[@deletemeforevs]

Yes! Keep on tinkering. I tried to make a ferrite mini, it worried but only with a long time and not that loud

[@tsbrownie]

@@deletemeforevs That's also my experience with small coils.

[@Pabloeskobar6680]

very good video :) its there a video how to fix headphones 2000 ohms and to fix coil ?

[@tsbrownie]

Thanks. Here's the earphone video: kzbin.info/www/bejne/qHzIhGmsiLSoac0 And how to design a coil: kzbin.info/www/bejne/fKiclpVjlqdgjrc

[@Ross-z1n]

VK3YE used small inductors in this KZbin video >>> Search "Trying galena in a crystal radio". Testing starts at the 10 minute mark. ...................... Wondering about your coil inductance estimations. One calculation parameter involves turns squared. (ie. Triple the turns gives nine times the inductance.) Using an online calculator adjusted to 130T =192.5uH the following circuit inductances were calculated. (For Total Coil inductance ... 130T =192.5uH) Antenna/Ground inductance ...20T = 4.6uH Resonant Tank inductance ... 110T = 138uH Diode Tap inductance ... 30T = 10.3uH Loading on the A/G and Diode windings would cause some variations in values but maybe marginal?

[@tsbrownie]

@Ross-z1n The measured values did not agree with calculated values. That's why I did the ratio thing. It is not perfect, but has gotten me close. Next I'm going to break open 1 of these inductors and see how the coil is oriented.

[@AndreeaMariaChiturusi]

You better try axial inductor in a future video, they are small but have some coil inside if u get what i mean..SMD components are too S.F for old analog projects like crystal radios and less reliable

[@tsbrownie]

I agree. The small, rectangular ones are axial if I remember from some I broke open. I have to break one of these I used in the video and see how it's constructed. I may have an orientation problem.

[@A3Kr0n]

Coil inductors sound better than solid state.

[@tsbrownie]

@@A3Kr0n And it's more accurate.

[@sebastian19745]

"in theory inductance is inductance". No, you are wrong, there are different inductances types. Like mutual inductance. A transformer is not just two coils, primary and secondary. Those inductors you are using, have you opened them? I think that they are made on pot core or something like that, that is why they do not work. The one station you received was because it was the most powerful or the nearest to your location? You need to have coupling inductances. Maybe try to simulate the equivalent circuit you have at 2:00 (that is an autotransformer basically), think about it?

[@tsbrownie]

@sebastian19745 I am going to open one. I assumed they were like the small rectangular ones where the coil is horizontal, but in fact they may be vertical. We shall see.

[@sebastian19745]

@@tsbrownie I just asked because I believe that the magnetic field is contained and is not interacting with the neighbor inductances. That is you may not have any mutual inductance, that is needed because the original circuit is an autotransformer.

[@tsbrownie]

@sebastian19745 I think that is also likely. We shall see. I don't give up until reality defeats me!

[@imnobody0034]

Stretch your antenna wire out.

[@tsbrownie]

@imnobody0034 It is 15 meters long. It's the same one I use in all my crystal radio videos so it's the "standard." A small, portable radio that requires a really long antenna is not very interesting.

[@jagmarc]

I read somewhere quite a few years ago of a 2 foot square frame antenna wound with thick wire. Didn't need any other antenna

[@AnotherPointOfView944]

Eh, there is no crystal in your crystal radio? If you replace the diode with a crystal and hair whisker contactor, then you have a crystal radio.

[@tsbrownie]

I have a few videos on that, but when experimenting one needs to vary 1 variable at a time. Adding a crystal would drag things out and make the results less reliable. Here are some of those crystal videos: kzbin.info/www/bejne/oYnZaJ6LmKZ8ec0 kzbin.info/www/bejne/d3_YhmudqKZ_sKs kzbin.info/www/bejne/hoKTlJ-Nmp2Bfbc kzbin.info/www/bejne/rH_ViYyqYq-ifKs kzbin.info/www/bejne/j2W1oJevdrh7oNE kzbin.info/www/bejne/iofTqYp5g5p3esU

[@thomasklima215]

Aww man thats bad - try to get a grip on coupled inductors.

[@tsbrownie]

@thomasklima215 Got it to work in the next vid. Now I'm running tests on coupling and orientation.