# Hi, center tap transformer, how to calculate?

Discussion in 'General Electronics Discussion' started by michael1978, Sep 6, 2018.

1. ### michael1978

388
2
Mar 17, 2012
Hi,
can somebody, explain me, HOW I HAVE TO CALCULTE this tapped transformer?
i have this site
www.zen22142.zen.co.uk/Theory/tunedcct.htm
i calculate Impedance for example of this circuit the total inductance, in serie with 1416n tapped 313n total round 1720n, there is 10.7Meg plus inductance 1720n = 115.636 Ohms, but this tapped inductance, how do i have to calculate to find imedance, with the same frequency, of other, THANKS...

4,275
1,147
Jun 25, 2010
What is 'n'?

3. ### Audioguru

3,268
701
Sep 24, 2016
"n" would be nH nano-Henries.

4. ### michael1978

388
2
Mar 17, 2012
what can be nanohenry

5. ### michael1978

388
2
Mar 17, 2012
Yes AudioGuru

6. ### michael1978

388
2
Mar 17, 2012
Hi Audioguru, do yu have any idea how to calculate L1, with the same frequency of L1 and L2 in serie

7. ### Audioguru

3,268
701
Sep 24, 2016
I never designed and built the IF transformer or discriminator for a radio, instead I simply bought an old one or took one from an old radio.

Two inductances in series have a total inductance that is their inductances added.
You do not know the amount of wiring or stray capacitance which affects the tuned frequency so the inductor is usually tuneable with a ferrite core that can be screwed in or out.

116
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Jul 6, 2012
9. ### Ratch

1,093
334
Mar 10, 2013
Calculte (sic) what result? You have describe what you want to calculate.

The impedance between what two points?

What component is 10.7 Megs? What imedance (sic) are we referring to now? What is "other"?

Ratch

10. ### kellys_eye

4,275
1,147
Jun 25, 2010
@Ratch - Take my advice - don't get involved in this...... if you value your hair.....

Harald Kapp likes this.
11. ### michael1978

388
2
Mar 17, 2012
Thanks man, but i will try to experiments...

12. ### michael1978

388
2
Mar 17, 2012
Hi Ratch, this is if amplifier, and i mean the impedance between 0 to 313nH, you measure with the same frequency center frequency 10.7MegHertz, for example two inuctors in serie between 0 to 313nH to 1420 is 1720(round) , and this total inductance 1720nH you have to find impedance with center frequency of 10.7MegHertz and that is 115.636 Ohms, but from 0 to 313nH i dont know how to find impedance……..

Last edited: Sep 7, 2018
13. ### michael1978

388
2
Mar 17, 2012
Hi Kellys ..............Why not??? man

14. ### Audioguru

3,268
701
Sep 24, 2016
The tuning capacitor is parallel with both inductances in series. The parallel LC resonates with a high impedance.
Since the LC resonates with a high impedance then the reactance of each coil is much less that the impedances in the circuit.

15. ### Ratch

1,093
334
Mar 10, 2013
I still don't have a definitive two points from where you want the impedance. I will guess that it is the two red dots on your schematic. That makes it two parallel branches, one of which contains L1 and C2 in series and the other just C1 by itself. The calculation of the impedance is shown below. As you can see, there is no resistance component in the impedance and the reactance is 192.42 ohms inductive. If you want the impedance from a different location or need an explanation, just ask.

Ratch

16. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,491
2,833
Jan 21, 2010
Because all the rest of us are trusting @Audioguru to assist you.

4,275
1,147
Jun 25, 2010
Clue #1.

18. ### michael1978

388
2
Mar 17, 2012
Hi, i understand now...………..thnx

19. ### michael1978

388
2
Mar 17, 2012
Hi, thank you i understand now ;-)

20. ### michael1978

388
2
Mar 17, 2012
Hi Kellys, i understand thnx

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