Max IVconic TGSL help

[Qiaozhi]

Dear Max and other
1-i need the the exact frequency value for TX and RX
2- the best inductance value for TX and RX

and no more

best regards

Search for the TGSL gift pack. It's all there.

[nakky]

Originally Posted by metaldetector107
Dear Max
i am realy confused i dont understand is it possible to explain it agin but easly please?
how about maching TX with RX frequency
cuz i dont understad resonance why seprate coil?
please i know i am troubling you but i have no choise

thank alot
best regards
Hi,
it's simple, you need to match tx inductance and rx inductance to make a good coil, then null it.
Now the inductance is due to many factors not only number of turns. You right pointed to effects of shielding and that's an issue, there are others like taping the wire tight, the more the more inductance you get at same number of turns etc

The free-oscillator strategy is only if you are perfectionist and wanna hi precision on resonant frequency, don't need really in most of the cases.

You need to match inductance, so at tx you'll do so when will find the tx frequency stay in the expected range : that you need when coil already shielded etc so at the end the frequency must stay in the limits described.

For rx the stuff is similar, but remember that in e.g. Tesoro's coils the rx coil has a bit more inductance, usually 6.2mH there like described in the table I wrote about... the link I posted.

Now if for tx coil you just need to match frequency (say 14.7Khz as example) and that with expeceted values of capacitor at tx oscillator, of course, for rx coil you need a step further ahead, some turns more there.

In tgs coil by Ivconic you'll see some numbers like 100 turns for tx coil... and 105 for rx coil: fine you have 5% more turns at rx, and something more inductance.... so if tx will be for example 5.8mH you'll get about 6.2 mH at rx coil that way.

As example make 6.2/5.8 = 1.068 (about) that means you'll get about 6.8% more inductance there... with 5% more turns.

That's cause inductance increase NOT linearly with turns number... but that's unimportant here... what you need is a bit more inductance at rx coil: that's cause this will give you the right phase shift at coil when on nulling phase, that's all we need to know, and tesoro made that way for this purpose.

So, leave all considerations about exact resonance at coils, and try to focus only on inductances and required phase shift/nulling of coil.

Much of what I wrote before is advanced stuff... needed just when try to put things on the extreme of performances.... but often boring and unuseful if you just need a working md.

Kind regards,
Max
__________________
-- submerged in troubles --

[Unregistered]

From which point you measure RX frequency?
With so gived datas and 15N on RX I have 14,7kHz for TX and same for RX but sens is week!
Not like it should be.Disc Ok

[simonbaker]

From which point you measure RX frequency?
With so gived datas and 15N on RX I have 14,7kHz for TX and same for RX but sens is week!
Not like it should be.Disc Ok

Don't confuse "RX signal frequency" with "RX tank resonant frequency".

"RX signal frequency" is alway exactly same as TX oscillator frequency -- only phase is different. Nothing to think about. You can't change it.

"RX tank resonant frequency" is the resonant frequency of the RX coil and the parallel capacitor (.015 uF in the TGS schematics). That is what most people are interested in.

You can compute "RX tank resonant frequency" by the formula Max gave above if you have exact measurements of RX coil inductance and parallel capacitor capacitance (neglecting small other effects). This is the formula:

f = 1 / (2 * pi * sqrt(L * C))

pi = 3.1415
L = inductance of RX coil. For example, use 0.0062 Henry (6.2 mH) by Max suggestion.
C = capacitance of capacitor. Use 0.000000015 Farad (.015 uF) as in schematic .

That gives you f, resonant frequency in cycles/second.

Or you can measure it using a signal generator and oscilloscope (frequency counter helps make more accurate).

The question is, what should resonant freq be? From other posts, I understand it is not critical, but should be somewhat greater than 14.5 kHz, maybe 16.5 kHz. That is safe value to make sure phase shift is correct. That's why Max recommend 6.2 mH for RX coil.

Your signal (oscillator) frequency 14.7 hHz is good. There can be many reasons sensitivity not good, but requires careful troubleshooting.

Regards,

-SB

[Unregistered]

Thanks
Simon.
Is 6,2mH with shield?

[simonbaker]

Thanks
Simon.
Is 6,2mH with shield?

Best if final coil (including shield and any wrapping) is 6,2 mH. I don't think shield by itself changes it much, but binding coil tighter will raise inductance, so finish coil ready to mount and check inductance.

But don't worry too much. If inductance is somewhat off, you can use formula and change capacitor to keep resonant frequency near 16.5 kHz. I think that is OK to do, but always best to stay with proven experience of others.

Cheers,

-SB

[satdaveuk]

Very interesting imformation I didnt even know this page exsisted, spent many hours experimenting with various frequencys and everything said here is what i experienced, effects of the coils when going above the 15Khz on the TX, the symtoms are the same as bad coil nulling, repeated signal on coil sweep, falsing etc.
I pushed the TX up to 17khz and tryed balancing the RX tank network, but it didnt want to know it, worked like one of those cheapys.
The test I was doing were with 8" Tesro stock coil, so next time I shall have a go with my test coils so im able to alter nulling
At this time im quite convinced that Tesro got the inductance of the coils spot on for this particular design which is 5.7-6.2 you can go a tad either way but nothing after 6.0-6.5mh if you go outside these boundries as previously said by simon on here you can start choping and changing components in the tank circuit etc but who really wants to do that, your better off spending your time and effort in building top notch coils, well matched and firmly wound faraday cage to prevent EMI etc.
Dont skimp with components, on these projects use good quality as Tesro do, and meter read resisters/capacitors for values/errors before they are installed on the PCB, may seem long winded at the time but could save you hours in the long run.
Regards

[ivconic]

Best if final coil (including shield and any wrapping) is 6,2 mH. I don't think shield by itself changes it much, but binding coil tighter will raise inductance, so finish coil ready to mount and check inductance.

But don't worry too much. If inductance is somewhat off, you can use formula and change capacitor to keep resonant frequency near 16.5 kHz. I think that is OK to do, but always best to stay with proven experience of others.

Cheers,

-SB

Agree!