Inductors and ferrite bars

Hello.

I wonder if some one can explain to me how the length of a ferrite rod with a wire wrapped round it
changes the behaviour of a LC tank circuit?

I have an AM receiver circuit that came as part of a kit. The capacitor can change from 0 to 160 pf.
According to the instructions I can tune this circuit down to 500KHz. I need to get down to 457KHz.

The inductor is 80 turns of wire on a ferrite bar. What is the ferrite bar used for?

I understand resonance and how to calculate it using capacitance and inductance.
IBut do not know how to construct the inductor to acheive the values i need.

Thanks for any help.

Google Loop-stick antenna.

Simple answer, add about 10 to 20 Turns, or shunt the tuning capacitor with about 50pF.

Do you have a signal generator or other source of signal at 475kHz?

Hi thanks for your help.

Yes I have both a signal generator and a RF transmitter transmitting on that frequency that I am trying to tune into.

So you are suggesting increasing the amount of turns of the inductor?
I thaught that would increase the inductance?
I was under the impression tha I needed to decrease the inductance?

I have been looking at loop stick stuff but most seem to be wound on pvc pipe.
I was wondering what difference the ferrite core makes.

If i remove the core I seem to loose ability to tune into the radio stations but
am able to pick up the transmitter with the lower frequency, (all be it a very weak signal.)

scubadog said:

So you are suggesting increasing the amount of turns of the inductor?
I thaught that would increase the inductance?
I was under the impression tha I needed to decrease the inductance?

Click to expand...

Your thoughts are wrong. As MikeML says, simply add 10-20 turns on the ferrite loopstick and it will do the trick. I would just analyze the guage of wire used on the loopstick and extend the turns by using the same kind of wire for couple of turns to tune down to 457KHz. Use a ferrite LC calculator if you want to perform precise calculations.

Can you post your receiver pictures to analyze the inside?

Thanks

I have attached a link to the circuit diagram.

https://www.electro-tech-online.com/custompdfs/2012/11/3063.pdf

The loopstick is made using 80 turns of litz wire.
seing as i do not have enough litz wire to add extra turns can i replace it with any other wire?

In that case, leave the loopstick and add more capacitance.

You can use .2mm enamelled copper wire to wind around 100 turns.You should be able to cover the frequency using the same 160p variable cap.

or use a 365pf variable cap..... they're common as dirt