On Tue, 28 Mar 2006 12:05:01 -0500, John Popelish
wrote:

But a choke with two wires wound through it is two inductors that also
have mutual inductance between them, and if that doesn't define a
transformer, what does?

Hi John,

Then you think of it as an air core transformer with series driven,
bucking sections. Now, what kind of practical transformer does that
define? 1:1 does not automatically spring to mind unless it is
isolating one circuit from the other. However, it is not the
transformer that does that, it is the choking ferrite and only in the
service of snubbing common mode currents.

With this in mind, do we add a characteristic of loss to the
definition? A lossy air core transformer with series driven, bucking
sections.

You are bordering on stretching the definition of power transformer
over the application of a BalUn. This is not always useful. So, what
does it transform? A balanced circuit to an unbalanced circuit (or
versa vice).

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Tue, 28 Mar 2006 12:05:01 -0500, John Popelish
wrote:


But a choke with two wires wound through it is two inductors that also
have mutual inductance between them, and if that doesn't define a
transformer, what does?


Hi John,

Then you think of it as an air core transformer with series driven,
bucking sections. Now, what kind of practical transformer does that
define? 1:1 does not automatically spring to mind unless it is
isolating one circuit from the other. However, it is not the
transformer that does that, it is the choking ferrite and only in the
service of snubbing common mode currents.

With this in mind, do we add a characteristic of loss to the
definition? A lossy air core transformer with series driven, bucking
sections.

Air core? It is a ferrite core transformer with two one turn
windings. One winding is the shield passing through the holes in the
cores and the other winding is the center conductor passing through
the windings. (view with fixed width font, like Courier)

|half of dipole
. |
Center cond.-----MMMM-+

I mainly wanted to know if it would work on 160 & 80m, I dont care
if it acts like a choke/balun only at higher frequencys as long as
as it doesnt interfere with 160 & 80s swr. Normally i just use coax
hooked to each leg cut to frequency, without a balun. Its allways
worked in the past years, i just thought it would be alot easier to use
the ready made balun than try and makeup a weatherproof
hanger

In article . com,
wrote:

I mainly wanted to know if it would work on 160 & 80m, I dont care
if it acts like a choke/balun only at higher frequencys as long as
as it doesnt interfere with 160 & 80s swr.

It should not interfere. If the ferrites don't have enough reactance
to make it act as an effective choke on 160/80, then it'll just "look
like" a foot or two of coax to the signals.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

wrote:
I mainly wanted to know if it would work on 160 & 80m, I dont care
if it acts like a choke/balun only at higher frequencys as long as
as it doesnt interfere with 160 & 80s swr. Normally i just use coax
hooked to each leg cut to frequency, without a balun. Its allways
worked in the past years, i just thought it would be alot easier to use
the ready made balun than try and makeup a weatherproof
hanger.

So what ohm reading do you read between two points on one of the cores?

John I will have to take it down and measure it, im going to do it
anyway because the balun will not load up like it should even with
wire on each leg cut to the proper length. I dosent dip with the dip
meter at the proper freq either, after i take it down ill post the
ohmeter results.

On 28 Mar 2006 11:02:44 -0800, wrote:

I dont care
if it acts like a choke/balun only at higher frequencys as long as
as it doesnt interfere with 160 & 80s swr.

Hi OM,

There is a world of improvement of understanding BalUns slated for
you, but
Its allways worked in the past years
suggests you should skip that line of inquiry and simply go back to
working your scheds. If you encounter problems, then is the time to
ask questions.

73's
Richard Clark, KB7QHC

On Tue, 28 Mar 2006 12:59:52 -0500, John Popelish
wrote:
With this in mind, do we add a characteristic of loss to the
definition? A lossy air core transformer with series driven, bucking
sections.

Air core? It is a ferrite core transformer with two one turn

Hi John,

If there's a transformer in the sense of windings; then it is an air
core, the ferrite is wholly transparent to the transverse currents.
You could remove the ferrite and it wouldn't make a bit of difference
in that sense of transforming.

this current mismatch would cause the transformer to
produce more or less voltage across the windings
In fact, nothing of that sort happens - at least not by your
description. The ferrite is simply bulk resistance inserted into the
common mode path. That is why common mode current is suppressed. The
same thing occurs in the coiled transmission line choke, but the
resistance is replaced by reactance. Again, common mode current is
snubbed by encountering this too.

The transformer property is in the isolation of the balanced circuit
from the unbalanced circuit through this resistive characteristic.

You are missing one path. The two from the source in the form of the
inner shield of the coax, and the center conductor, and the one from
the load in the form of the outer shield of the coax (same shield, but
isolated circuits). Further, there is no flux linkage of the two
conductors coming from the source. Their magnetic lines never break
the cores, whereas the common mode current does break the core which
thus inserts the resistance of the ferrite.

73's
Richard Clark, KB7QHC

On Tue, 28 Mar 2006 17:39:52 -0800, Richard Clark
wrote:

Further, there is no flux linkage of the two
conductors coming from the source.

That was not correctly expressed, the flux between the two are tightly
bound and:
Their magnetic lines never break
the cores, whereas the common mode current does break the core which
thus inserts the resistance of the ferrite.

Richard Clark wrote:
On Tue, 28 Mar 2006 12:59:52 -0500, John Popelish
wrote:

Air core? It is a ferrite core transformer with two one turn

Hi John,

If there's a transformer in the sense of windings; then it is an air
core, the ferrite is wholly transparent to the transverse currents.

I said that. It is a common mode transformer.

You could remove the ferrite and it wouldn't make a bit of difference
in that sense of transforming.

The short length of the two conductors passing through the ferrite is
certainly a poorer transformer (less mutual inductance between them)
if you remove the cores.

this current mismatch would cause the transformer to
produce more or less voltage across the windings

In fact, nothing of that sort happens - at least not by your
description. The ferrite is simply bulk resistance inserted into the
common mode path.

Make that, "impedance (mostly inductive, if the ferrite is well suited
to the frequency)" and I agree.

That is why common mode current is suppressed. The
same thing occurs in the coiled transmission line choke, but the
resistance is replaced by reactance. Again, common mode current is
snubbed by encountering this too.

I agree with this, except that the purpose of the ferrite is to
increase the common mode inductance of the section of coax passing
through it, not add resistance. Some resistance is inevitable,
because no ferrite is lossless, but the intention is for inductance.

The transformer property is in the isolation of the balanced circuit
from the unbalanced circuit through this resistive characteristic.

Try transmitting through such a resistance and you are going to lose a
lot of your power.

You are missing one path. The two from the source in the form of the
inner shield of the coax, and the center conductor, and the one from
the load in the form of the outer shield of the coax (same shield, but
isolated circuits).

I can't parse this. There are two metal conductors entering the
choke, and two exiting it. All currents pass through those 4 conductors.

Further, there is no flux linkage of the two
conductors coming from the source. Their magnetic lines never break
the cores,

I think you mean by this that a normal unbalanced signal in a coax has
no magnetic field external to the shield. It is all between the
center conductor and the shield. And I agree that this is what you
are trying to accomplish by adding this two conductor choke between
the coax and the balanced antenna. Without it, there would be some
magnetic field from a net (uncanceled) current and voltage on the
outside of the shield that would cause the coax to radiate. And the
voltages and currents fed to the balanced antenna would not be equal
and opposite (balanced) but somewhat unbalanced. There would also be
non equal currents in the center conductor and shield. I think we
agree on all that, but have a different picture of how a choke balun
corrects these problems.

whereas the common mode current does break the core which
thus inserts the resistance of the ferrite.

The common mode current causes flux in the core, and the conductors
passing through that flux produce a voltage proportional to the rate
of change of that flux, just as the conductor passing through any
inductor would. The transformer aspect is that since both conductors
pass through the exact same rate of change of flux, there is the same
voltage produced at the ends sticking out of the core, and this
voltage gets algebraically added to what is already there. If the
inductance of each winding is high enough (5 to 10 times the coax
impedance) a very small common mode current is enough to produce a
large enough voltage across the ends to the two conductors to correct
most of the unbalanced to balanced coupling.

Admittedly, there is no need to get this inductance (including mutual
inductance) with the aid of ferrite around the coax. You could just
wind the coax into an air core transformer. But it would be
considerable larger than one made with a high permeability core,
though, probably lower loss.