Toroid Rings.

Hello John,

first, is it really 60kHz - ie 60000 Hz, nearer audio than what most would call RF

If so - what is you are trying to build - I can't see what you would want a toroid - if you want a ferrite rod aerial that isn't a good start.

Is the application for fun or for serious stuff, and I'm guessing you want to pick up the MSF signal from Anthorn ?

MK

Hello, Michael, and thanks for the reply.

The request is serious in that I'm trying to learn, but hobby in that I now do electronics as a retired electronics man (with little knowledge of coils and most other things radio!!)

You're right. It's about MSF. To that end I bought one of those Canadian receivers (yet to arrive) but I also use the opportunity to wind coils, try this, try that, try to understand the maths, etc. So I decided to see if I could make a simple TRF radio with a couple of tuned RF / audio stages. If all else fails I still have the bought receiver, but that will teach me nothing about LCR circuits. So you see my quest is a bit of both hobby and serious. I will probably try a crystal stage to see how I get on with that, too, but I kind-a want to make a tuned stage just for the hell of it ... to see if I can make it work. Learn something about ferrites and so on.

I looked at toroids because my reading-up seemed to show they might work, and I get to learn a bit about those parts, their data sheets, etc; I get to learn even if toroids don't work like that!! Self teaching is always full of difficulties, and I'm at that stage with the coils where I need a hand as the Q of my built coils is always too low (B&K 880 LCR meter) with 90 being about the best no matter what I wind them on, or how, or with.

There we are. That's the story.

John

A toroid won't work like a ferrite rod aerial - put simply there is no way for the magnetic component of the RF to get into the core and generate emf in the coil;.

I was interested in this too - so I've ordered some ferrite rods from Amazon

https://www.amazon.co.uk/gp/product/B074W4RNCV/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I found this article which is fun:

The Creative Science Centre - by Dr Jonathan P. Hare

I'm thinking of a minimal RF amplifier and using an STM32Hxxxx processor with its 16 bit ADC to do a SDR (Software Defined Radio)  and demodulator.

How far I get will be time limited (as usual).

@John

60kHz is quite a low frequency for LC filters - the Ls need to be big and can be expensive  and/or quite lossy. But active RC filters work very well in this frequency range.

The MSF signal uses on/off modulation with 100ms time slots, so a bandwidth of about 20 to 30Hz at the input to the de-modulator seems about right. That's quite hard to do

with analogue filters but easy in maths - which is why I fancy the ADC and processor for the filtering.

MK

I wasn't sure if John was planning a separate antenna connected to the resonant circuit or not, but the rod acting as antenna + resonant circuit is way better. A microcontroller-based SDR sounds really cool : ) There's another low-frequency that I was interested in recently, which was to do with heart-rate straps (i.e. as used for the gym). They work at around 5kHz apparently, so I was tempted to build up something for that to decode it, but in the end decided to locate a BLE one. I still have the 5kHz strap, so may try to experiment with it one day.

Guys ....

Thanks for the responses.

Just to clear it up, I’m *not* trying to use a toroid core as an antenna. I’ll mess with a ferrite rod for that.

The toroids are for a kind of IF strip but, of course, it’s not IF it’s at the antenna frequency to make a TRF receiver (but at one, fixed frequency = 60KHz). These coils will be tuned with a C to make a tank cct amplified by a BJT or an FET or a chip.

My reading tells me that the best Q is always a compromise, but it is to be had with the largest practical core. Then the fewest possible turns to reduce capacitive losses between windings and to the core. Further, the core material should be designed for the frequency of interest. In addition the skin effect @ frequency of the wire needs to be chosen correctly: I already have Litz wire that should work. (Did I miss anything to reduce losses?)!

I have some 40mm 3E27 cores laying around. They should be ok. Experimentally, 10 turns of .75mm enamelled Cu wire makes about 1.5 mH. I resonated that with the desired C. Signal if fed in with a loop close by and is extracted to a scope with a pickup turn on the core. Or, the inductor (no capacitor) is connected to my B&K 880 LCR meter where Q, D, ESR, Z, DCR, R, theta can be measured. I’ve tried different gauge wires wound in different ways to get an idea of how these things affect the inductor properties for the same value of L - just for learning.

As mentioned, all this is pretty new knowledge to me so I’m likely to have got stuff wrong and missed important points.

John

Thanks. This is mostly further down the line for me. If I can get a clean and amplified 60KHz signal it’ll be an achievement in itself for me.

Hello. I’m afraid I have no idea how to make a blog. I’m an old person. It would be different if I were young. Ha ha.

It's dead easy on E14.

When you are logged in, click the create button at the top right hand of the screen, next to your name, and then select Blog Post.

From there on it's pretty straightforward.

MK

Thanks. But what Is a blog? What does it do and what is it for?

Here's a link to one I prepared earlier.

Capacitor Leakage Current over Temperature

It describes some experiments I did to measure some aspects of the performance of capacitors.

When I get my ferrite rods I'll make an aerial and blog about it - just like writing the experiment up in a notebook like we did in the olden days.

MK

blog is short for web log. element14 provides tools and resources to create, store and publish notes and logs on projects that members create.

I'm old too .

I think your question has been answered in my absence by several knowledgeable Element14 members.

The blogs are a nice way of sharing our fun and experiences in electronics (and related disciplines) with like-minded folk. The modern day equivalent of a show-and-tell I guess. Once someone makes a blog (plenty of photos and pictures/diagrams) they often get a flurry on interesting comments - sometimes the discussions go on for weeks. If someone writes a blog on something they may highlight issues they had or are experiencing - again fellow E14 members often add helpful comments.

It really is a great community - I encourage you to at the very least log in often and watch the content, or better still just jump straight in .  If you are ever in doubt, just ask in the same way you started this discussion.

I'm old too .

I think your question has been answered in my absence by several knowledgeable Element14 members.

The blogs are a nice way of sharing our fun and experiences in electronics (and related disciplines) with like-minded folk. The modern day equivalent of a show-and-tell I guess. Once someone makes a blog (plenty of photos and pictures/diagrams) they often get a flurry on interesting comments - sometimes the discussions go on for weeks. If someone writes a blog on something they may highlight issues they had or are experiencing - again fellow E14 members often add helpful comments.

It really is a great community - I encourage you to at the very least log in often and watch the content, or better still just jump straight in .  If you are ever in doubt, just ask in the same way you started this discussion.

Thanks, all. I now know what a blog is!

Returning to my original post, perhaps I should have asked about the best way to make a high Q coil for a tank circuit at 60KHz.

I now realise that it might or might not involve a toroid. And I also realise that a tank circuit at this frequency might or might not be the optimum way to get the best selectivity.

Maybe I should be seeking guidance on the best way to make a high Q coil at 60KHz. I'm assuming there will be some basic guidelines, even if in the end such a concept is just not good enough?

Views?

Thanks.

John

If (decades old) memory serves, high Q coils are characterized by large diameter air core windings with gaps between each turn of low impedance wire.

Also, it's a compromise. If you choose a material and/or dimensions such that you need fewer turns, then Q can be higher. So you'd think you should go for a material that need fewer turns, but such material varies more with temperature, which then means your high Q resonant circuit might shift in frequency. Plus, the larger it is, the more resistance. So then you could choose thicker wire to reduce resistance but then you may not have space to get as many turns to reach the required inductance. You could space the turns but then that affects inductance and you may not be able to fit the amount of turns without thinner wire. In summary the parameters are interdependent, and I don't know of any software that would help. You could design such software to iterate, varying each parameter bit-by-bit, and give you an answer, but it's a big task maybe.

At 60kHz your best bet is a pot core, if you want to use an inductor.

You need a gapped core (ones without gaps are good for power but less good for filters), made from a ferrite suitable for filters in the frequency range you are interested in.

The EPCOS (TDK) https://www.mouser.co.uk/ProductDetail/EPCOS-TDK/B65811F315A48?qs=sGAEpiMZZMs2JV%252BnT%2FvX8JpxZdCKKXlRTnIVKnqpr08%3D

will do.

The Al value is 630nH per turn so 100 turns will get you 6.3mH.

It's hard to find anyone in the UK with a good range of pot cores now so you'll need to go to Mouser for these. (They have a UK based web site).

You will need a bobbin and clips to hold the cores together.

I'll leave you to do some reading - download the data sheet from Mouser.

This core can accept an adjuster.

MK.

The ferrite rods just turned up

On their way back !

They were just put 5 per little jiffy bag and able to smash each other up.

MK

Hi Michael, Oh that's a shame. They were of a decent length too.

I tried a whip antenna just now into a HF receiver to see if it would pick it up in CW mode to record a WAV file in case it helps for your code. I've put the zipped-up MSF wav file here it is recorded from about 12:11 BST (11:11 UTC) today (Fri 4th 0ct 2019) and the recording is just over four minutes long. The receiver was in CW mode, set to 1kHz tone. The tone is audible, but would need some signal processing (the antenna wasn't very good, it was just a short length antenna).

EDIT: After some filtering in an audio app (I don't have matlab on this PC) this is the spectrum, for about 5 seconds. The horizontal scale is seconds, i.e. running from 30.0 sec to 35.2 sec. The carrier off period is visible, seems to be off-periods of 200, 200, 300, 300, 300 msec in this portion.

Thanks for the data sheet link. I’ve downloaded it, thanks.

Before going much further I’m going to see if I can discover what sort of Q I should be aiming for. Within reason the higher the better, maybe? I suppose radio constructors’ books, etc, from the 1940s might help - if I can get them - and there is the RSGB and ARRL publications.

Thanks again for the link: all this stuff is useful!

Best

J

What a mess with the rods! Can’t understand why these folk have such a lack of comprehension when it comes to packing fragile stuff for the post.

That's awful. Clicking 'like' seemed slightly inappropriate - what I really meant by clicking is support for you.

I'm assuming you didn't order these from Farnell/Avnet/Element14 - their packing always seems good.