Question about the values of inductor coils.

[mkvl]

I would like to know if this two inductor coils in the picture have the same value? Or if it should be has the same value?.
Thank you.

[CountChocula]

Not necessarily—it depends on the application. The number of windings could be the same if all you care is line isolation, or it could be significantly different if you need to convert from high to low impedance to drive your speakers (this used to be a particular issue with valves, as I understand). Like with so many other things that have to with amplifiers, Rod Elliott has a great article on the subject (if you aren't familiar with his site, it's a great resource).

[RoGeorge]

A 1:1 transformer (which will imply same value for coils) is more an exception than the norm, so no, usually they are not the same value.

About the posted schematic, it should say somewhere in the description how many turns has to be in each coil, and their physical dimension (length/diameter/core type, etc).

[TimFox]

For RF tuned circuits, the self-inductance of each coil may differ, but the mutual inductance may well be less than the value for unity coupling.
These parameters are used to effect impedance matching in narrowband circuits.

[MathWizard]

Do you have any circuit simulator like LTSpice ? There's also more graphically oriented circuit simulators, that show the flow of currents.

I should try 1 of them also, on some SMPS gate drive circuits I'm trying to understand. I'm about to desolder some SMD parts, to really find out what they are, because it doesn't work right in LTSpice. Trying to identify sot23 SMD transistors and diodes is hard sometimes.

[TimFox]

In Spice itself, the syntax for two (linear) inductors L1 and L2 coupled to each other is

L1     20  21  <value>
L2     30  31  <value>
K12   L1  L2  <value>

where L1 and L2 are self-inductances (note that in each case the first node listed is the + terminal, to define polarity of the coupling)
and the coupling co-efficient K12 is defined by

K₁₂ = M₁₂ / (L₁ L₂)^1/2  < 1

where M₁₂ is the mutual inductance between the two inductors (polarity sensitive).

[AK6DN]

I would like to know if this two inductor coils in the picture have the same value? Or if it should be has the same value?.
Thank you.

That is not really two inductor coils, as in separate inductors. It is physically a transformer. which is built using two physically interleaved inductors as a single assembly.
The turns ratio can be 1:1, or whatever your circuit requires. The nominal inductance of the winding(s) is also variable, depending on the application (ie, audio vs radio frequencies).
So I think you misunderstand what that graphics symbol in the schematic implies.

[radiolistener]

this transformer can be 1:1 or whatever you want. It depends on your load impedance.

[TimFox]

I would like to know if this two inductor coils in the picture have the same value? Or if it should be has the same value?.
Thank you.

That is not really two inductor coils, as in separate inductors. It is physically a transformer. which is built using two physically interleaved inductors as a single assembly.
The turns ratio can be 1:1, or whatever your circuit requires. The nominal inductance of the winding(s) is also variable, depending on the application (ie, audio vs radio frequencies).
So I think you misunderstand what that graphics symbol in the schematic implies.

That graphic symbol is not as specific as you  state.  It could be two inductors that do not overlap but are wound on the same coil form.
It suggests a 1:1 turns ratio, but that is just sloppy use of a template.
A careful drawing would show the polarity with heavy black dots at one end of each coil.

[Circlotron]

In that circuit the primary side inductance will be whatever is needed to resonate with the capacitor connected across it. The secondary side can have less turns so it can feed a lower voltage higher current into a low impedance, or more turns so it can feed a higher voltage lower current into a high impedance. Or anything in between.

[mkvl]

I know that's a transformer symbol, I just used the term inductor.
Thank you.

[vk6zgo]

That graphic symbol is not as specific as you  state.  It could be two inductors that do not overlap but are wound on the same coil form.
It suggests a 1:1 turns ratio, but that is just sloppy use of a template.
A careful drawing would show the polarity with heavy black dots at one end of each coil.

The labelling "output" implies a transformer.
Unless the phase in each winding is important, there is little need for "black dots".

As the circuit purports to be "basic tuned", they could have dispensed with the secondary winding.
Transformer coupling is common, but other techniques are used-----some RF circuits may be RC coupled, or there may be additional LC coupling circuitry other than the collector tuned circuit.

[radiolistener]

if you want to know which impedance ratio to select for transformer, you can use 1:1 transformer and measure it's output impedance. Then measure your load impedance. Then divide one impedance with another and you will get which impedance ratio is best suitable for your needs.