On Sep 2, 10:22*am, Ian White GM3SEK wrote:
Dan wrote:
On Sep 1, 4:20*am, Ian White GM3SEK wrote:
Dan wrote:
On Aug 31, 3:07*pm, Ian White GM3SEK wrote:
Dan wrote:
On Aug 28, 2:26*am, Ian White GM3SEK wrote:

In other words, people with limited antenna opportunities are often the
ones who need a balun - or more accurately, a common-mode choke - the
MOST.
Technically I would have to disagree with calling even a 1:1 balun the
same thing as a common mode choke. *A CM choke is an EMI prevention
device intended to filter out RF components generated in a circuit,
away from the feed of a power source, usually an electrical mains.

That is too far narrow a definition *of a "common mode choke",
especially the reference to electrical mains. The term is widely applied
to transmission line for both digital data and analog RF signals.

A common mode choke is used in RF applications, very true, but it
serves a filtering purpose,
not a conversion of unbalanced to balanced energy transfer or vice
versa. A common mode choke that operates well will turn
unwanted RF into heat or cause it to dissipate in its core or a
resistor etc..

Common-mode chokes, and filters in general, do NOT aim to "turn unwanted
RF into heat"! That is a total misunderstanding of the whole concept.

A CM choke aims to present a high impedence to unintentional RF. Once
"choked" by the high impedance,
the enrgey must either reflect or be aborbed somewhere in the circuit
or the core as real power. What is it that you cannot
understand about the term "choke"?

I'm slightly encouraged that the key word "reflected" has now crept into
your description. It wasn't there in what you wrote previously.

[Snip similar]

In a perfect situation, with a balanced feedline, the only kind of
current and voltage you have IS common mode!

What??? *You know that statement didn't come out right, so how much of
the rest did you really mean?

I give up! You need some education in this area.

I give up too - *at last, something we can agree about.

My main worry is that anyone *else* might have tried to gain some
education from your confused statements on this particular topic.

--

73 from Ian GM3SEK * * * * 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek- Hide quoted text -

- Show quoted text -

Many US amateurs do not understand how a balun works. I expected
something better from our European counterparts who seem to understand
power transmission
concepts better than their US counterparts.

On Tue, 2 Sep 2008 19:31:18 -0700 (PDT), wrote:

In a perfect situation, with a balanced feedline, the only kind of
current and voltage you have IS common mode!

Many US amateurs do not understand how a balun works.

How true - not even fundamental terminology.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

...
How true - not even fundamental terminology.

73's
Richard Clark, KB7QHC

When you are right, you are right; and, YOU GOT THAT ONE RIGHT! :-)

Regards,
JS

--
It is like a nightmare where the public servants are the people which
the police are supposed to protect us from!

Richard Clark wrote:
wrote:
Many US amateurs do not understand how a balun works.

How true - not even fundamental terminology.

http://en.wikipedia.org/wiki/Balun (see 1st photo)
"This is a simple RF *choke* which works as a *balun* by
preventing signals passing along the outside of the braid."

From "The IEEE Dictionary":
"balun (1) A network for the transformation from an
unbalanced line or system to a balanced line or system,
or vice versa."

From an Unabridged Webster's:
"balun - a device for converting a balanced line into
an unbalanced line and vice versa."

10 PRINT "A W2DU balun is both a choke and a balun!"
20 Goto 10
--
73, Cecil http://www.w5dxp.com

On Sep 3, 2:10*pm, Cecil Moore wrote:
Richard Clark wrote:
wrote:
Many US amateurs do not understand how a balun works.

How true - not even fundamental terminology.

http://en.wikipedia.org/wiki/Balun(see 1st photo)
"This is a simple RF *choke* which works as a *balun* by
preventing signals passing along the outside of the braid."

*From "The IEEE Dictionary":
"balun (1) A network for the transformation from an
unbalanced line or system to a balanced line or system,
or vice versa."

*From an Unabridged Webster's:
"balun - a device for converting a balanced line into
an unbalanced line and vice versa."

10 PRINT "A W2DU balun is both a choke and a balun!"
20 Goto 10
--
73, Cecil *http://www.w5dxp.com

I agree that a balun operating at 14 MHz would be a choke when
operating at 70MHz.

wrote:
I agree that a balun operating at 14 MHz would be a choke when
operating at 70MHz.

You would do well to agree that a well-designed W2DU balun
operating at 14 MHz is choking the heck out of the 14 MHz
common-mode current in order to achieve the balun function.

You seem to have the IEEE definitions of differential
signals and common-mode signals exactly reversed. Because
of that misconception, might you be the one who doesn't
understand how baluns work?
--
73, Cecil http://www.w5dxp.com

On Sep 3, 7:18*pm, Cecil Moore wrote:
wrote:
I agree that a balun operating at 14 MHz would be a choke when
operating at 70MHz.

You would do well to agree that a well-designed W2DU balun
operating at 14 MHz is choking the heck out of the 14 MHz
common-mode current in order to achieve the balun function.

I wouldn't say it was choking the common mode.mode current, I would
say it is isolating it from diff mode current by simply creating an
isolated ground reference point (you could define it at centertap if
you were so inclined). Of course I would agree that the impedance
between diff mode current at the input and CM current in the output
had better be very high, infinity would be best, but the finite
impedances to load and source respectively should match the balun. If
you want to call the ground isolation function "choking", that use of
this colloquialism is fine with me but FYI that is not the traditional
vernacular for that that application. Also, if the W2DU balun is
referred to as the "ugly balun", I do believe the use of a bifilar
winding around an air core to create an RF transformer has been around
for more than 100 years so I do not understand why it is so-named
after a contemporary ham. It is rather simple to go from bifilar
enameled copper to using the shield and inner conductor of a coax as
"bifilar" conductors. All of this stuff is pretty basic EE (Associate
level, not even Bachelors) and I hesitate to spend much more time on
it.

wrote:

...
I wouldn't say it was choking the common mode.mode current, I would
say it is isolating it from diff mode current by simply creating an
isolated ground reference point (you could define it at centertap if
you were so inclined). Of course I would agree that the impedance
between diff mode current at the input and CM current in the output
had better be very high, infinity would be best, but the finite
impedances to load and source respectively should match the balun. If
you want to call the ground isolation function "choking", that use of
this colloquialism is fine with me but FYI that is not the traditional
vernacular for that that application. Also, if the W2DU balun is
referred to as the "ugly balun", I do believe the use of a bifilar
winding around an air core to create an RF transformer has been around
for more than 100 years so I do not understand why it is so-named
after a contemporary ham. It is rather simple to go from bifilar
enameled copper to using the shield and inner conductor of a coax as
"bifilar" conductors. All of this stuff is pretty basic EE (Associate
level, not even Bachelors) and I hesitate to spend much more time on
it.

One thing I can say for sure, you are an idiot ... good luck.

What an utter waste of time ...

Regards,
JS

--
It is like a nightmare where the public servants are the people which
the police are supposed to protect us from!

wrote:
If
you want to call the ground isolation function "choking", that use of
this colloquialism is fine with me but FYI that is not the traditional
vernacular for that that application.

In 1953, my first ham transmitter had an RF choke to allow
DC to reach the 6146 plate while choking the RF thus forcing
it to follow a different path through the pi-net. RF "chokes"
have been around since before I was born.

From "The IEEE Dictionary": "choke - a device for preventing
energy ... in a given frequency range from taking an undesired
path."

That's exactly what the RF choke in my Globe Scout did in
1953 and that's exactly how a W2DU balun works today.
--
73, Cecil http://www.w5dxp.com

On Sep 3, 7:18*pm, Cecil Moore wrote:
wrote:
I agree that a balun operating at 14 MHz would be a choke when
operating at 70MHz.

You would do well to agree that a well-designed W2DU balun
operating at 14 MHz is choking the heck out of the 14 MHz
common-mode current in order to achieve the balun function.

You seem to have the IEEE definitions of differential
signals and common-mode signals exactly reversed. Because
of that misconception, might you be the one who doesn't
understand how baluns work?
--
73, Cecil *http://www.w5dxp.com

Cecil, if a transmission line operated in the way you think, it would
be radiating fields all along its length transmitting RF all along the
length of the line. Nothing would get the antenna. The conductors in
the lines MUST carry mirror image currents and voltages to indeed
cause the cancellation of fileds you speak about. THAT is how energy
gets to the antenna. Ever hear of a ground loop?