36 mH

[hoehoe]

Please help me to make 36 mH inductor with air core ,to use in AM transmitter

i want the no. of turn , the cu.wire dim (SWG ,OR AWG ),THE CORE DIM.

THANK YOUUU

 

[BobW]

Are you sure about the inductance value? 36 mH seems huge for use in an AM transmitter, unless you're just using it for a choke somewhere. Even then, it's rather large. For medium wave circuits 5 to 10 mH is usually big enough for a choke.

 

[MrAl]

Hi,

Wow, a 36mH air core inductor? That must require a large number of turns. Maybe this needs a ferrite core.

 

[Hero999]

Are you trying to make a large loop antenna?

 

[colin55]

It sounds like you are trying to make the antenna coil.
Wind 60 turns around the edges of a packet of 20 cigarettes using 0.25mm winding wire.

 

[BobW]

It would be useful to see a schematic of this project so that we could see exactly where the coil is supposed to go. As I mentioned before, I can't think of anywhere in an AM transmitter circuit where a 36 mH coil would be required. A loop antenna would be no more than about 200 µH.

To make a 36 mH choke, start with a 3/8" dia. x 3/8" long bobbin. You can make it out of cardboard if you can't find anything else that's suitable. Wind it with multiple layers of #32 AWG wire until the total winding diameter is about 1". It will be about 1500 turns, and will require about 260 feet of wire. Note, that this coil geometry will only be useful as a choke (not as part of a resonant circuit), and even then, not a great choke. I think that if a 36 mH coil is really required, then it's probably better to buy one.

 

[hoehoe]

Dear ALL
THANKS
I WILL ATTACH THE CIRCUIT

 

[Hero999]

How are you going to tune it?

The parasitic capacitance of a 36mH air coil will more than likely swamp a variable capacitor to tune to tune to the AM broadcast band.

 

[BobW]

The parasitic capacitance of a 36mH air coil will more than likely swamp a variable capacitor to tune to tune to the AM broadcast band.

That's why I don't think this is part of the tuned circuit. More likely used as a choke in the collector/drain/plate or emitter/source/cathode circuit.

 

[Nigel Goodwin]

That's why I don't think this is part of the tuned circuit. More likely used as a choke in the collector/drain/plate or emitter/source/cathode circuit.

But why would you use such a ludicrously high value?. Generally you use a transformer to AM modulate a transmitter, but not much use foir a great big choke. You also wouldn't use ferrite for the core for such a large choke, you would use a laminated core as for a valve output transformer.

 

[THESTOCKSGUY]

Let's start out with some history and get to the circuits of Old......

Once upon a time, there was a war and Foxholes for the soldiers to hide in. No communications made the stay
inbearable for some, and those that knew basic electronics made 'Foxhole Radios', simple gadgets that broke
the monotony for many. Get some tols and learn about those turns of wire on toilet paper cores, how to use a
razor and safety-pin for a 'channel changer', and what a 'whisker' is. This was MY FIRST radio built when I was
9 years old, got KJR for three days then the novelty wore off and I hungered for MORE. My next stop was a kit from
HEATHKIT (obsolete company) and built a television. GREAT FUN !!!!!


Foxhole radio - Bizarre Labs

 

[BobW]

But why would you use such a ludicrously high value?

That's what I'd like to know too. Sometimes the circuit designer uses whatever is on hand, and it ends up in the schematic even though it's far from optimum. Could be a typo too. We'll have a better idea once we see the schematic.