Hi, i am searching in internet, for ferrit rod antenna, but i dont know how to calculate, of the formula
here is the circuit, i put you for example this circuit, L1 60 turn, L2 10 turn, L3 5 turn
so is also transformer, can somebody help me to solve i know to make but i dont know how is the formula thanks

 

You need the formula only if you want to use a different value variable capacitor or a different frequency.
The inductance of a ferrite rod with a known number of turns is used with the formula for inductance and capacitance to determine the frequency.

 

Hello,

The value of the coil will depend on the size and material of the ferrit rod.
Amidon sells several sizes for AM radios.
For LW material 33 is often used:
http://www.amidoncorp.com/33-material-ferrite-rods/
For MW material 61 is often used:
http://www.amidoncorp.com/61-material-ferrite-rods/
A common size is a diameter of about 1 cm and a lenght of 7 to 12 cm.

The attached PDF will tell you more about the ferrit material proporrties.

Bertus

 

You need the formula only if you want to use a different value variable capacitor or a different frequency.
The inductance of a ferrite rod with a known number of turns is used with the formula for inductance and capacitance to determine the frequency.

HI AudioGuru thnx, i know to determine the frequency, for example L1 and vc1 make a tuned circuit for min and max take care a vc1, but coupling inductor L2 and L3, what they do?

You need the formula only if you want to use a different value variable capacitor or a different frequency.
The inductance of a ferrite rod with a known number of turns is used with the formula for inductance and capacitance to determine the frequency.

 

Hello,

The value of the coil will depend on the size and material of the ferrit rod.
Amidon sells several sizes for AM radios.
For LW material 33 is often used:
http://www.amidoncorp.com/33-material-ferrite-rods/
For MW material 61 is often used:
http://www.amidoncorp.com/61-material-ferrite-rods/
A common size is a diameter of about 1 cm and a lenght of 7 to 12 cm.

The attached PDF will tell you more about the ferrit material proporrties.

Bertus

Hi Bertus thanks, but i cant open the file....

 

HI AudioGuru thnx, i know to determine the frequency, for example L1 and vc1 make a tuned circuit for min and max take care a vc1, but coupling inductor L2 and L3, what they do?

L2 and L3 provide positive feedback for the regen circuit. Signal energy flows into L3 from the transistor collector and is coupled 180 phase shifted out of L2 into the transistor base.

 

Hello,

The attached file is just a simple PDF.
You will need a PDF reader to read the PDF.
Foxit-reader is a simple one:
https://www.foxitsoftware.com/pdf-reader/

For your ease I will post the table here as PNG:



Bertus

 

Some ref material -

http://www.c-max-time.com/tech/antenna.php

http://g3rbj.co.uk/wp-content/uploads/2013/10/Web_-The_Inductance_of_Ferrite_Rod_Antennas.pdf

Regards, Dana.

 

L2 and L3 provide positive feedback for the regen circuit. Signal energy flows into L3 from the transistor collector and is coupled 180 phase shifted out of L2 into the transistor base.

yes AudioGuro, but wht they select L2 10turn L3 5 turns

L2 and L3 provide positive feedback for the regen circuit. Signal energy flows into L3 from the transistor collector and is coupled 180 phase shifted out of L2 into the transistor base.

I Read that, but why exactly they chose L2 10 TURN, L3 5 TURN? how they calculate, i have another they chose L1 45 turn and L2 11 turns, i dont understand the second and third inductor, and how they chose to value,

 

Hello,

The attached file is just a simple PDF.
You will need a PDF reader to read the PDF.
Foxit-reader is a simple one:
https://www.foxitsoftware.com/pdf-reader/

For your ease I will post the table here as PNG:

View attachment 150484

Bertus

i have foxit reader, but he did not open, but today he open, you know Bertus, i dont know how to select the second and third inductor?
thanks for informations

 

Some ref material -

http://www.c-max-time.com/tech/antenna.php

http://g3rbj.co.uk/wp-content/uploads/2013/10/Web_-The_Inductance_of_Ferrite_Rod_Antennas.pdf

Regards, Dana.

Thanks,, my problem is i dont know wich value of inductor L2 and L3 to select, how they calculate, whe they exactly the put the valu of L2 10 turns, and L3 5 turns, how he calculate?

 

Hello,

L1 is the tuning coil.
L2 is the coupling coil.
L3 is the feedback coil.

The ratio of L2 and L3 is fixed by the design of the circuit.
Also the start and ending of the coils is important, as when the L3 is mounten the wrong way, the circuit will not work.

Bertus

 

Hello,

L1 is the tuning coil.
L2 is the coupling coil.
L3 is the feedback coil.

The ratio of L2 and L3 is fixed by the design of the circuit.
Also the start and ending of the coils is important, as when the L3 is mounten the wrong way, the circuit will not work.

Bertus

Yes Bartus i know, for that i say, L1 i know how to selct but L2 and L3, for example if i make a ferrid rod for my specifik frequency so i know how to select the L1 AND VC, but for L2 or L3 i dont have idea how many turns to turn, of you have to read somewhere?​

 

Hello,

L2 and L3 are not frequency dependent.
Only the ratio and coil directions are important.

Bertus

 

Hello,

L2 and L3 are not frequency dependent.
Only the ratio and coil directions are important.

Bertus

Hi Bertus, but this is my problem, why somebody use 50 turn and copling 30 turn
of why the use 45 turn and coupling 11 turn, what is the purpose of L2 or L3, they do something in circuits and i dont understand, for that i am here to help me somebody for coupling coils.....

 

L3 is the regeneration coil that transformer couples into coil L2. You need to learn about regeneration. Look in Google for Regeneration Radio Circuit. It is a very very old and very very cheap radio circuit. It might not work well today since there are many more radio stations.

 

L3 is the regeneration coil that transformer couples into coil L2. You need to learn about regeneration. Look in Google for Regeneration Radio Circuit. It is a very very old and very very cheap radio circuit. It might not work well today since there are many more radio stations.

Hi AudioGuru, i just dont knw to select the desired turns L2 or L3

 

Hi AudioGuru, i just dont knw to select the desired turns L2 or L3

It's not really critical. L3 is the primary input coil so you need sufficient (but not too high so P1 can be used to adjust the drive strength) reactance at the operating frequency and turns to generate sufficient flux to couple to the other coils. L2 is the regen feedback secondary with twice the turns of L3 so there is a voltage and impedance step-up to better match the impedance and drive requirements of the transistor base circuit.

 

It's not really critical. L3 is the primary input coil so you need sufficient (but not too high so P1 can be used to adjust the drive strength) reactance at the operating frequency and turns to generate sufficient flux to couple to the other coils. L2 is the regen feedback secondary with twice the turns of L3 so there is a voltage and impedance step-up to better match the impedance and drive requirements of the transistor base circuit.

Thanks man