Working frequency

[jroux]

We can calculate the working frequency of a coil with inductance of tx :4.57uh and rx:10.47uh , capacitor on oscilator 30nf, its possible or i need a scope.

[WM6]

What is your question?

Your data are wrong. It should be mH not uH (except if you build GPR).

If you asking about (CC or DD) coil nullng, you do not need scope. You need working TX stage of your detector and good mV meter.

But it is hard to build mentioned coils without inductance-meter and frequency meter is welcome too. Scope (plus knowledge) can replace this two, so it is on yours what equipment you chose.

[Flash1940]

I get 429.83 Khz. Are you sure your inductance might be 4.57 mHY ????.....if so then the frequency would be 13.59 Khz. This doesn't count the parasitic capacitance introduced by your cable....which would lower the frequency a little.

[WM6]

Probably capacitor is 300nF and not 30nf.

[Overtheedge]

I often make use of the old LC Constant formula:

F²=25330/LC or LC=25330/F²

Where F is in MHz, L is in μH and C is in pF.

It is only approximate due to parasitic capacitances within the circuit layout and the inter-electrode capacitance within the coil (inductor) windings.

I tend to choose L and C by a reactance of roughly 300-400Ω at the frequency of interest.
eric

[Flash1940]

That's a pretty good rule of thumb design method. In Ham radio circles....we do tuned circuits around 250Ω....and shoot for a Q of over 10 or so. Some of the circuits above 50 MHz need to be silver plated due to skin effect. You MD guys aren't bothered by any of this...

[scs]

[WM6]

[ATTACH]25218[/ATTACH]

Excellent demo scs, on how a little practice check can replace thons of theories.

[jroux]

Sorry tx: 4.57mh and rx:10.47mh concentric coil double o, wire 0.3mm, capacitor on oscilator 30nf, MD with 9v battery, i've just mV meter. I want just the total frequency of the coil in Khz.
Many thanks for this good description i think that will be effectly 14Khz.
Regards.