is voltage balun right choice?
 

I've recently put up a 140' dipole fed with ladderline. My tuner is
separate from my rig, and is an unbalanced unit. So, I use a balun on the
tuner output to hook the ladderline to.

I've been told that I should have a voltage balun in this application. I
was surprised to hear this, as I expected to hear use a current balun.

Is the voltage balun the right one for this application?

is voltage balun right choice?
 

RB wrote:

I've recently put up a 140' dipole fed with ladderline. My tuner is
separate from my rig, and is an unbalanced unit. So, I use a balun on the
tuner output to hook the ladderline to.

I've been told that I should have a voltage balun in this application. I
was surprised to hear this, as I expected to hear use a current balun.

Is the voltage balun the right one for this application?

Only if you want your feedline currents to be unbalanced.
Your antenna is a lot like the one described on my web
page below that uses a 1:1 choke-current-balun and needs
no conventional tuner, the most efficient configuration
I could come up with. As can be seen from the current
maximum point graph on my web page, ~100 feet is a good
compromise length for the ladder-line for such an antenna.

A lot of hams will tell you to throw up a random length of
ladder-line and feed it through a 4:1 voltage balun. That's
usually not good advice and often results in a poor balun
function on one or more bands. If one doesn't know approximately
what impedance is being seen by the balun, one cannot predict if
it will function or not. The free version of EZNEC can predict
the approximate impedance seen by the balun. www.eznec.com
--
73, Cecil http://www.qsl.net/w5dxp/notuner.htm

is voltage balun right choice?
 

Cec,

As an aside, there appears to be a little confusion about the various
uses of baluns which arises from their uncertain perhaps misleading
descriptions.

Because of the way balun winding-wires are run, they are often
described as transmission line transformers.

There are --

Voltage Baluns, Current Baluns and Choke baluns.

As I see it, Voltage Baluns have a definite voltage/impedance/turns
ratio and are true impedance transformers. They may be used as either
balanced-to-unbalanced windings, or be balanced-to-balanced, or be
unbalanced-to-unbalanced. Balanced windings may be centre-tapped.
One winding may be common to both primary and secondary windings.

Choke Baluns consist of a pair of wires wound together around a
ferrite core. The two wires may be of coaxial form or may consist of
a twisted pair or just a pair of wires laid alongside each other. The
two wires together form a transmission line of calculable impedance
and loss.

But a Choke Balun hss no impedance or voltage ratio. It is incorrect
to refer to it as having an impedance ratio such as 1-to-1.

A Choke Balun does indeed behave as an impedance transformer from one
end of its line to the other. But the transformation ratio is
indeterminate. The ratio depends on frequency and line length as with
any other transmission line.

The effects of inserting a Choke Balun between an unbalanced tuner and
a balanced transmission line to the antenna can be beneficial insofar
as tuner settings are concerned.

But in general, the length of line on a choke balun should not exceed
1/8th or 1/10th of a wavelength at the highest frequency of use. This
is not too difficult to achieve in the HF range of 1.8 or 3.5 to 30
MHz.

But I do not understand what is meant by a Current Balun.

Perhaps Roy, who is very good at it, could define what is a Current
Balun if there is such a thing. And while he is about it, Voltage and
Choke Baluns.

He may choose to give them different names. But his views can only be
beneficial to the mislading waffle which surounds them.
----
Reg.

is voltage balun right choice?
 

Reg Edwards wrote:
But a Choke Balun hss no impedance or voltage ratio. It is incorrect
to refer to it as having an impedance ratio such as 1-to-1.
But I do not understand what is meant by a Current Balun.

Reg, the words, "choke" and "current" have become synonymous
when used as an adjective to describe baluns. A choke-balun
*is* a current-balun, usually a 1:1. N:1 current baluns exist
where N is not equal to one. Sometimes, an extra winding on
the toroid ensures that the currents are balanced.

Perhaps Roy, who is very good at it, could define what is a Current
Balun if there is such a thing. And while he is about it, Voltage and
Choke Baluns.

Try: http://www.eznec.com/Amateur/Articles/Baluns.pdf

Also: http://www.w2du.com/r2ch21.pdf

Current baluns balance the feedpoint currents and voltage baluns
balance the feedpoint voltages. Since unbalanced currents cause
radiation from the feedline, current baluns are considered
superior for amateur radio applications. The W2DU choke balun is
a member of the subset of current baluns.
--
73, Cecil http://www.qsl.net/w5dxp

is voltage balun right choice?
 

No, a current balun is the desired beasty in this case.

"RB" wrote in message
. ..
I've recently put up a 140' dipole fed with ladderline. My tuner is
separate from my rig, and is an unbalanced unit. So, I use a balun on the
tuner output to hook the ladderline to.

I've been told that I should have a voltage balun in this application. I
was surprised to hear this, as I expected to hear use a current balun.

Is the voltage balun the right one for this application?

is voltage balun right choice?
 

A choke (or current) balun is the correct choice.

The input impedance of the transmission line to the antenna varies all
over the shop from one band to another. So there is no definite
impedance to which the transmitter is to be matched.

A voltage balun is designed to match between two definite known
impedances of a given ratio, for example 4-to-1, 300-to-75 ohms,
values which never exist at your particular place in the system.

A choke or current balun is not intended to match one impedance to
another. It is intended only to allow, without loss, the transition
from a balanced line to an unbalanced tuner or transmitter.

Because the choke balun is in fact a short length of transmission line
wound on a ferrite core, an impedance transformation does occur
between one end and the other. But what the antenna line input
impedance is transformed to doesn't matter. It is just another
impedance for the tuner to handle and, as likely as not, the tuner
will handle it just as well. Just a change in L and C settings.
----
Reg, G4FGQ.

is voltage balun right choice?
 

Reg Edwards wrote:
A choke or current balun is not intended to match one impedance to
another.

Reg, there are 4:1 current baluns. See Figs A3-3,4 in
Roy's Balun article.
--
73, Cecil http://www.qsl.net/w5dxp

is voltage balun right choice?
 

Cec, a choke balun has an indeterminate ratio.

A choke balun which the man asked about, is, as you say, a current
balun.

I don't doubt that there are some forms of current baluns which have a
definite ratio. But they have more than two wires. They can be used to
transform one admittance or susceptance to another. ;o)

One thing for sure - they are all transmission line transformers -
for the want of a better name!

In some ways they are remarkable components. They should have been
invented 100 years before alongside ordinary L,C, R & G. But they had
to wait for the invention of ferrites which I understand did not occur
until the early 1940's in wartime Holland. But I would not be
surprised if somebody comes along with the idea that the invention was
in Bell Labs in the 1930's. Even before the Smith Chart which was an
adaption of similar charts in use in the late Victorian Age.

In the 1950's I met an American engineer who told me that in 1945
there were Americans looking round bombed-out German radio factories
and by chance came across some tiny top hats with narrow brims and
with 3 fine wires sticking out of one end. "What on Earth are these"
they asked.

I could go on. It's the Devil which makes me say such things. ;o)
----
Reg.

is voltage balun right choice?
 

You might find it instructive to take a look at
http://eznec.com/Amateur/Articles/Baluns.pdf.

Roy Lewallen, W7EL

RB wrote:
I've recently put up a 140' dipole fed with ladderline. My tuner is
separate from my rig, and is an unbalanced unit. So, I use a balun on the
tuner output to hook the ladderline to.

I've been told that I should have a voltage balun in this application. I
was surprised to hear this, as I expected to hear use a current balun.

Is the voltage balun the right one for this application?

is voltage balun right choice?
 

Good replies. Thanks.

So: does the commonly available choke balun (round cylinder with coax
connectors on each end, and ferrite beads inside the cylinder) allow us to
put unbalanced feed in one end, and get balanced feed on the other?

Or, are they ununs?

is voltage balun right choice?
 

A properly operating choke (current) balun will cause the currents in
the two conductors to be balanced (equal and opposite) at both ports. So
I guess you could call it a balbal if you want.

Why would anyone want a device that causes the currents at both ports to
be unbalanced?

Roy Lewallen, W7EL

RB wrote:
Good replies. Thanks.

So: does the commonly available choke balun (round cylinder with coax
connectors on each end, and ferrite beads inside the cylinder) allow us to
put unbalanced feed in one end, and get balanced feed on the other?

Or, are they ununs?

is voltage balun right choice?
 

On Sun, 27 Nov 2005 01:29:29 -0600, "RB"
wrote:

Good replies. Thanks.

So: does the commonly available choke balun (round cylinder with coax
connectors on each end, and ferrite beads inside the cylinder) allow us to
put unbalanced feed in one end, and get balanced feed on the other?

Or, are they ununs?

I suggest you take a look at this:

http://www.w2du.com/r2ch21.pdf

73
Danny, K6MHE

email: k6mheatarrldotnet
http://www.k6mhe.com/

is voltage balun right choice?
 

OK. I read that most excellent article.

I think Figure 21-4 (A) definitively answers my question about the ferrite
bead choke balun. Yes, I can put unbalanced feed in one end, and get
balanced output on the other.

Thanks again for all the good info.

is voltage balun right choice?
 

RB wrote:
So: does the commonly available choke balun (round cylinder with coax
connectors on each end, and ferrite beads inside the cylinder) allow us to
put unbalanced feed in one end, and get balanced feed on the other?
Or, are they ununs?

Since they function by choking RF on the outside braid, they
can function as either baluns or ununs. If RF is choked and
not flowing on the outside braid, then differential currents
are forced to flow in the two remaining conductors be they
parallel wires or the inside wire and braid of the coax.
--
73, Cecil http://www.qsl.net/w5dxp

is voltage balun right choice?
 

A choke balun allows you to go from unbalanced to balanced. If you check
Walter Maxwells site and review Chapter 21 (IIRC) of reflections. He gives a
test setup that will aid in understanding.

"RB" wrote in message
. ..
Good replies. Thanks.

So: does the commonly available choke balun (round cylinder with coax
connectors on each end, and ferrite beads inside the cylinder) allow us to
put unbalanced feed in one end, and get balanced feed on the other?

Or, are they ununs?

is voltage balun right choice?
 

RB wrote:
I've recently put up a 140' dipole fed with ladderline. My tuner is
separate from my rig, and is an unbalanced unit. So, I use a balun on the
tuner output to hook the ladderline to.

I've been told that I should have a voltage balun in this application. I
was surprised to hear this, as I expected to hear use a current balun.

Is the voltage balun the right one for this application?

Dear RB,
I was working on a "linear-loaded" dipole recently. I
got pretty confused
with many, many different opinions. I would suggest that you read
an article in
an 1995 QST about, "How to get the MOST out of your "T" type
antenna tuner"
IF you go to the web site and go to the search engine, you will find
this issue.
I wish that I would have found it sooner. It explained
the "process" very
well. I have photo-copied the article for passing around at my
local club. It is
very good.
Getting on 160m with a very small lot IS a
CHALLANGE ! I've
learned a whole bunch by searching the net. Most of it involves
trying this an'
that. BUT, we all need a place to start.


73's, Paladin

is voltage balun right choice?
 

I'll try to answer that.
Voltage baluns are designed to provide equal voltages on the
outputs, such as those needed for balanced antennas. They help to keep
the balance against external influences, such as nearby metal bodies
and such.
Current balun are used with unbalanced loads, such as windom
antennas, when it's needed to qeep the currents as equal as possible.
This is done in order to minimize radiation from the line, which is
more corrent dependent than voltage dependent.
Choke baluns serve to break the path between the load and the
source so as to prevent energy to flow in a common mode fashion aleng
the line (usually from the load to the source). the name itself-the
full name, that is- " common mode choke" is self explanatory.
Alex 4Z5KS

is voltage balun right choice?
 

I'll try to answer that.
Voltage baluns are designed to provide equal voltages on the
outputs, such as those needed for balanced antennas. They help to keep
the balance against external influences, such as nearby metal bodies
and such.
Current balun are used with unbalanced loads, such as windom
antennas, when it's needed to qeep the currents as equal as possible.
This is done in order to minimize radiation from the line, which is
more corrent dependent than voltage dependent.
Choke baluns serve to break the path between the load and the
source so as to prevent energy to flow in a common mode fashion aleng
the line (usually from the load to the source). the name itself-the
full name, that is- " common mode choke" is self explanatory.
Alex 4Z5KS