Calculating the coils of a transformer balun

[goulart]

Hi!

I'm preparing myself to go QRPp and now I'm doing my best to design and construct a balun to delete the so called I3 current that flows on the outside of the coaxial ground mesh. I've tried many, many internet sites, and I do have learned a lot about coils, inductance and baluns but no one has already given me a hint about the calculation, or, answered my question:

HOW MANY TURNS OF WIRE I have to wind in an air core 40mm in diam. to delete the spurious current and still NOT AFFECT THE WANTED RADIO SIGNAL?

What I have in mind is 1 coil "A" at the end of the coaxial, 1 coil "B" at the end of the coaxial mesh, and, 1 coil "C" linking after the "A" with before the "B" coil.

 

[Alun]

What are you talking about?

Baluns are RF impedance matching transformers that are used to match the impedance of an aerial to a peice of co-axil cable or to a transmitter or reciever, at low frequencies they are wound around ferite cores at higher frequencyies they are air cores and at microwave they are often conductors of differant lengths paced near each other.

What are you trying to achieve, you may know more about this subject than the people here so we might be able to learn from you even if we can't help you so could you please provide more information.

 

[goulart]

Dear Alun (Electronics god)
Didn't all my words suffice for you? Really?
Ed Goulart

 

[Alun]

Dear Alun (Electronics god)

Electronics god is a title only appointed to me because I've made more than 500 posts here (no great achievement). I do have some general electronics knowledge as I have an HNC in electronics engineering (about 1/3 of a degree) but this doesn't make me an RF engineer by any stretch of the imagination.

Didn't all my words suffice for you? Really?

Short answer, no, long answer, I'll go though your origional question and highlight the parts I don't understand.

Hi!

I'm preparing myself to go QRPp and now I'm doing my best to design and construct a balun to delete the so called I3 current that flows on the outside of the ground coaxial mesh.

What is:
QRPp?
ground coaxil mesh?

I've tried many, many internet sites, and I do have learned a lot about coils, inductance and baluns but no one has answered my question:

I also know almost all there is to know about coils and inductance but I always thought baluns were for impedance matching, do they have any other uses?

HOW MANY TURNS OF WIRE I have to wind in an air core 40mm in diam. to delete the spurious current and still NOT AFFECT THE WANTED RADIO SIGNAL?

What do you mean by "spurious current"? and won't the number of turns depend on the frequency and impedance of the load or source?

What I have in mind is 1 coil "A" at the end of the coaxial, 1 coil "B" at the end of the coaxial mesh, and, 1 coil "C" linking after the "A" with before the "B" coil.  Nothing more than a transformer balun.

What's a coaxial mesh? Do you mean an ordinary coaxial cable which is often referred to as a transmission line?

These coils should be for a range of output currents from an 100mA to an 100W.

Won't the current be different from the primary to the secondary of the transformer?

If you can help me, please...
PY2TKS/pp2, Goulart

I'd like to help you but first I need to understand what you're trying to do, is this just simple source to load impedance  matching or is it something more complex? ???

Edit:
I've done a Google search and learned more about baluns, this has really made me appreciate how poor the RF part of the course I took is. A balun is more about matching an un-balanced system like a coaxial to a twisted pair impedance matching can also be achieved with the same device. However this doesn't help me answer your question or povide me with definitions for the turms I don't understand in your post.

 

[goulart]

Dear Alun, Greetings!

Thankyou very much for taking time to investigate about the balun subject.
I do have searched a lot in the net about it and, to say the truth, it seems to me that no one has the answer... at least not the way I'm trying to find it...