LC parallel tank circuit

[bertus]

Hello,

In the old days we used a grid dip meter to determine the frequency of a LC circuit:
http://sm0vpo.altervista.org/use/gdo.htm

Bertus

 

[Rajinder]

Hi all,
I have attached a simulation in Simetrix, as you can see the voltage is at a minimum on the resonant frequency. What have i done wrong? The 1K was added to create a voltage to be monitored.
thanks in advance

 

[WHONOES]

The LC circuit should be in series with the 1K resistor as previously stated.

Edit: Have just seen your pictures. The response is correct. I intended you to put the 1K resistor on the top of the LC circuit so that it goes to the + arm of the ac source. It would then give the response previously described.

 

[Rajinder]

The LC circuit should be in series with the 1K resistor as previously stated.

Edit: Have just seen your pictures. The response is correct. I intended you to put the 1K resistor on the top of the LC circuit so that it goes to the + arm of the ac source. It would then give the response previously described.

Hi
Just to confirm the resistor should be placed in between the lc parallel circuit and the sine wave generator?
I will try this. However, i have seen the configuration that i have shown in a text book, hence the confusion.
I will give it a try.
Thanks

 

[Rajinder]

Hi,
I have just tried putting the resistor in series (see attached schematic and output - LC Parallel Circuit.pdf). It shows voltage at a max and current at a minimum as you mentioned.
I took this a bit further by adding a transistor (see attached schematic - LC Parallel with Transistor). I am not sure that is the response, I think it may be as the LC is a high impedance circuit hence passes everything out of the collector of the transistor, is that correct? is there a better way to test the second circuit?

Any help would be appreciated.

Best regards,
Raj

 

[WHONOES]

Your circuit won't do much as the transistor is not properly biased.

See PDF's attached.

 

[Rajinder]

Your circuit won't do much as the transistor is not properly biased.

See PDF's attached.

Hi,
Thanks for the reply and the pdf documents. Really appreciate you taking time out to help.
I have just wired the LC Parallel circuit (as in my message). The scope was placed at the output i.e. across the LC Circuit. However, I saw no change in voltage as I changed the frequency. I sweeped from 100KHz to 350KHz, the resonant frequency should be about 190KHz. Am I not scoping at the correct point?
Thanks for the circuit you sent and graph. I do not fully understand the circuit and the graph, could you give me a brief description. Thanks again.

 

[WHONOES]

Have a look at the link below. It explains about basic transistor biasing.

Transistor Biasing and the Biasing of Transistors (electronics-tutorials.ws)

 

[Rajinder]

Have a look at the link below. It explains about basic transistor biasing.

Transistor Biasing and the Biasing of Transistors (electronics-tutorials.ws)

Thanks. I simulated the circuit (my circuit) in simetrix and at resonance the voltage was high, current low. However doing this practically resulted in the voltage being at a minimum.
I will show pics of my set up.
Thanks again.