Excellent article! It really did a good job of explaining why the
current path on the outside of the coax exists and causes problems.
Also an excellent description of the various types of baluns that had
this rookie puzzled.

More please!

jtm

On 19 Mar 2005 08:37:07 -0800, "Jim Miller" wrote:

Excellent article! It really did a good job of explaining why the
current path on the outside of the coax exists and causes problems.
Also an excellent description of the various types of baluns that had
this rookie puzzled.

More please!

jtm
Yes, Roy's article in the Compendium is excellent, as are all of Roy's
contributions to our art. In his article he referenced my work with
baluns, which appeared in QST for March 1983. This article is also
available on my web page at www.w2du.com for those who don't have a
copy of that issue of QST.

Walt Maxwell, W2DU

"Walter Maxwell" wrote
Yes, Roy's article in the Compendium is excellent, as are all of Roy's
contributions to our art. In his article he referenced my work with
baluns, which appeared in QST for March 1983. This article is also
available on my web page at www.w2du.com for those who don't have a
copy of that issue of QST.

Walt Maxwell, W2DU

Walt & Roy, thank you both very much for your lifetime of service to radio.
Have either of you analyzed any the numerous popular Radio Works "Current
Baluns"? I was advised many years ago that the current-type balun was more
effective for use with a dipole, and have used Radio Work's baluns on both
dipole and random wires with success. But my measure of success is not
analytical, as your studies have been. Operating a center-fed dipole at it's
resonant frequency, slightly below that, and significantly above it, are the
specific inquiries wrt current baluns - would a voltage balun be more
effective in any of those conditions? Radio Works current baluns the same
kind used in your studies?

Thanks for your comments, and the great participation of all in this group.

Jack Painter
Virginia Beach, Virginia

On Sat, 19 Mar 2005 14:38:32 -0500, "Jack Painter"
wrote:

would a voltage balun be more effective in any of those conditions?

Hi Jack,

The typical Voltage BalUn is constructed in such a way that one lead
violates the isolation offered by the Current BalUn method. There are
examples found for the same application of the 4:1. One is the
Guanella, the other is the Ruthroff. If you examine the Ruthroff
model, you will notice that one lead of the load (antenna) is
connected directly to the source without a choking intervention. On
the other hand, both leads are choked by the Guanella.

By common usage, the Guanella is generally described as a Current
type, where as the Ruthroff is described as a Voltage type BalUn.
Current or Voltage, the more important feature is in the choking.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
"Jack Painter"
wrote:

would a voltage balun be more effective in any of those conditions?

Hi Jack,

The typical Voltage BalUn is constructed in such a way that one lead
violates the isolation offered by the Current BalUn method. There are
examples found for the same application of the 4:1. One is the
Guanella, the other is the Ruthroff. If you examine the Ruthroff
model, you will notice that one lead of the load (antenna) is
connected directly to the source without a choking intervention. On
the other hand, both leads are choked by the Guanella.

By common usage, the Guanella is generally described as a Current
type, where as the Ruthroff is described as a Voltage type BalUn.
Current or Voltage, the more important feature is in the choking.

73's
Richard Clark, KB7QHC

Thanks Richard. I have never seen the internal construction of the Radio
Works BalUn, but it is claimed to be a current-type device. It's function
as a choke was the only reason for including it in the designs of my antenna
systems. I see that Reg as well as yourself remind us that is indeed their
primary purpose. Too bad so many may have been fooled into using
voltage-type baluns when that appears to be an inappropriate choice for may
applications. I was curious what applications would benefit from such a
voltage-balancing device.

Jack

Jack Painter wrote:

Walt & Roy, thank you both very much for your lifetime of service to radio.
Have either of you analyzed any the numerous popular Radio Works "Current
Baluns"?

No, since I figured out what baluns do and wrote the article, I've never
purchased a balun since I know how to make effective ones myself. When I
wrote the article, the popular commercial baluns were all "voltage
baluns", and I'd like to think that the article was a factor in causing
the gradual changeover of commercial products to "current baluns".

I was advised many years ago that the current-type balun was more
effective for use with a dipole, and have used Radio Work's baluns on both
dipole and random wires with success. But my measure of success is not
analytical, as your studies have been. Operating a center-fed dipole at it's
resonant frequency, slightly below that, and significantly above it, are the
specific inquiries wrt current baluns - would a voltage balun be more
effective in any of those conditions?

Your question indicates that my article failed to explain one of its
major points. The answer is no, a voltage balun is not more effective
than a current balun in any antenna/feedline application. If the antenna
is perfectly balanced, the third winding in the voltage balun will carry
no current and does nothing. If the antenna isn't balanced, the presence
of the voltage balun's third winding will prevent balanced currents in
the elements. So at best the voltage balun does as well as a current
balun, and otherwise it degrades balance.

Radio Works current baluns the same
kind used in your studies?

Sorry, I've never purchased one and taken it apart. You might try asking
them.

Thanks for your comments, and the great participation of all in this group.


You're welcome. I'm surprised and frankly disappointed that so many
people haven't seen the article before. It's been in print for 20 years,
and frequently mentioned on this newsgroup and elsewhere. There are a
lot of other good articles in the _Antenna Compendium_ series -- people
who don't have a set have been missing a lot. But it seems like, more
and more, that the web has become the sole source of information for a
growing number of people. Make that the web, AM talk radio, and Fox news.

Roy Lewallen, W7EL

On Sat, 19 Mar 2005 14:38:32 -0500, "Jack Painter"
wrote:


"Walter Maxwell" wrote
Yes, Roy's article in the Compendium is excellent, as are all of Roy's
contributions to our art. In his article he referenced my work with
baluns, which appeared in QST for March 1983. This article is also
available on my web page at www.w2du.com for those who don't have a
copy of that issue of QST.

Walt Maxwell, W2DU

Walt & Roy, thank you both very much for your lifetime of service to radio.
Have either of you analyzed any the numerous popular Radio Works "Current
Baluns"? I was advised many years ago that the current-type balun was more
effective for use with a dipole, and have used Radio Work's baluns on both
dipole and random wires with success. But my measure of success is not
analytical, as your studies have been. Operating a center-fed dipole at it's
resonant frequency, slightly below that, and significantly above it, are the
specific inquiries wrt current baluns - would a voltage balun be more
effective in any of those conditions? Radio Works current baluns the same
kind used in your studies?

Thanks for your comments, and the great participation of all in this group.

Jack Painter
Virginia Beach, Virginia

Thanks, Jack, for the nice words--they're appreciated.

Walt

Roy and Walter,

CHOKE BALUNS.

Keep it simple. Why make a song and dance about it?

The pair of wires wound on a choke balun behave as an inductive choke
for longitudinal currents and as a transmission line for balanced
currents.

The two circuits, line and choke, behave independently of each other.

The actual current on a wire, if anyone should ever wish to know, is
just the arithmetical sum of the other two.

All authors omit to say that the the pair of transmission line wires
need not be coaxial. They can be a balanced twin line such as a length
of stranded flexible speaker cable. Or just a pair of insulated wires
laid alongside each other. Or twisted.

Not only is the twin-line mechanically more convenient to construct,
it has electrical advantages. Its Zo is intermediate between the high
and low terminating impedances. Typically Zo is about 120 -130 ohms.
The geometric mean of 50 and 300 ohms is 122 ohms. Not that this
matters very much because the device is never terminated in its
nominal impedances.

Twin line also has a higher velocity factor than 50-ohm coax.

The length of line wound on the choke behaves as an impedance
transformer. So it seriously, but not harmfully, affects the impedance
presented to the tuner. The tuner LC settings may be beneficially
affected. Otherwise the transformation ratio, which heavily depends on
frequency, is not of consquence.

Preferably, the length of twin-line wound on the choke should be less
than 1/8th of a wavelength long at its own velocity at the highest
operating frequency.

It is not too difficult to construct a choke balun which has
sufficient inductive choking reactance at 1.8 MHz without the
transmission line exceeding 1/8 wavelengths at 30 MHz.
----
Reg, G4FGQ

A few further comments.

For perfectionists, the attenuation along a twin-line wound on a choke
balun, is appreciably less than a coaxial line of about the same
length.

This is due to the lower Zo of the coax and also due to the very small
inner coaxial conductor diameter and its higher loss resistance.

This is not of great conseqence. The length of line involved is quite
small anyway. Less than 1/8th wavelengths at the highest frequency of
interest.

The power-handling and voltage-handling ability of twin-line is also
greater than coax line.

So, in general, a choke balun wound with Radio Shack, 18 SWG speaker
cable, is cheap, easier to construct, works better, and is more power
efficient than the small-bore coax usually used.
----
Reg, G4FGQ

Walt, I intended to include a link to your article and looked on your
web site for it before I posted my article. But I didn't find it in the
index. Where is it relative to your home page? I'll add a link to it.

Walt's article was really the first one I ever saw that explained the
phenomenon of currents on the inside and outside of the coax -- my
article is really just an extension of his work.

Roy Lewallen, W7EL

Walter Maxwell wrote:

Yes, Roy's article in the Compendium is excellent, as are all of Roy's
contributions to our art. In his article he referenced my work with
baluns, which appeared in QST for March 1983. This article is also
available on my web page at www.w2du.com for those who don't have a
copy of that issue of QST.

Walt Maxwell, W2DU