Re: what makes it a balun????

"Brian Reay" <see@xxxxxxxxxxxxxxx> wrote in message
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"class_a" <class_a@xxxxxxxxxxx> wrote in message
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But that is the crux of the argument. If a choke balun is wound on a
bucket with seven turns (as stated in the original post, and assumed to
be a regular sized bucket) there is a very high chance it will NOT have
the same impedance as one wound with the optimum dimensions and will
therefore not be as effective as the constructor thinks it is.


I suggest you look at how the inductance, and therefore the impedance
varies, for a given number of turns but with different winding diameters.
Also, allow for the fact that coupling between the "input" and "output"
will decrease for a larger coil if they are diametrically opposed.


You could also look at the various formula for calculating the inductance of
single layer coils to see how the relationship between winding radius (and
thus diameter) and inductance varies.

There are several formulae, some may look a little daunting to do this with
but remember the length, number of turns, wire diameter and permeabilities
are fixed. Only the diameter / radius/ CSA and inductance are changing
between coils.

Once you've learned how the inductance varies with diameter (ie a positive
or negative relationship) maybe you can focus on how you think the physical
size of the inductor (with a given inductance) impacts its "choking" action
in the application. That is really the question I'm asking you.

If you feel confident, try looking at how the length of wire used changes
wrt coil diameter and the related relationship between required turns and
wire length. That will help you consider the losses factor.

(The maths is about on a parr with a GCSE course work project.)

--
73
Brian, G8OSN
www.g8osn.org.uk


Now your amateur licence is free, why not send at least £15 per year to
support the
Radio Communications Foundation or STELAR?





.

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