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.

An ideal common-mode choke would dissipate zero heat energy, and a
successful real-life choke will dissipate only a tiny fraction of the
available RF power.

When you insert a common-mode choke, you are inserting a large impedance
into the pathway of the common-mode current. The RF current
distribution throughout the entire antenna/feedline/ground system will
adjust to take account of this new impedance. As a result, most of the
common-mode current will be DIVERTED away from its former pathway, and
will flow instead in the antenna.

The details are complicated, but the concept that the choke DIVERTS
common-mode current away from the feedline is reasonably accurate. (By
contrast, the concept that it "turns unwanted RF current into heat" is
just plain wrong.)

If the choke is doing its job, the new value of common-mode current
(I_cm) flowing through the choke will be much less than the previous
value. The power dissipation in the choke will then be (I_cm)-squared x
R, where R is the resistive part of the choke's impedance at that
frequency. Note that I_cm is the small amount of common-mode current
that remains *after* having inserted the choke - not the value before!
The practical outcome is that a higher choke impedance will give *lower*
heat dissipation in the choke itself.

If a common-mode choke is getting hot, it isn't working. Unfortunately
there are many chokes that don't have a high enough impedance to handle
the full range of real-life situations. If a choke is not able to
suppress the common-mode current to a low enough value, then in some
situations it will get hot [1, 2]. But PLEASE don't imagine that is
how common-mode chokes are intended to work!

[1] http://www.w8ji.com/Baluns/balun_test.htm

[2] http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf

Also see other pages and publications from the same authors.



A
balun is intended to change the feed from an unbalanced transmission
line to a balanced output, for example, for connection to a balanced
transmission line or to an antenna such as a dipole. With the balun,
we wany NO reduction in RF current flow.

What exactly do you mean by that?

You do not want the balun to operate hot (ir to dissipate heat as you
do with a CM choke filter). You strive for 100% transfer of energy and
settle for the best
you can get. With a CM choke, you try to filter and dissipate unwanted
back-RF. Any back RF from your balun
should be converted to unbalanced transfer back to the source. You
reduce back-RF by matching impedances (which can also involve baluns
but not the 1:1 application discussed here). If you try to filter it
the unwanted back-RF, you will also end up filtering the forward
energy transfer. Of course, that would be an undersirable situation.


Sorry, but that is so confused I can't even begin to unpick it... except
by pointing to "you try to filter and dissipate unwanted back-RF". In so
many different ways, that is NOT what we're trying to do. Tug on that
loose strand, and the whole thing unravels.



And also, what exactly do you mean by "balanced" in the context of a
feedline?

For a 2 conductor feedline, the V in each conductor is 180 degrees out
of phase with each other. Same with I.

Yes.

One conductor is +90 degrees
and the other is -90 degrees with respect to earth.

No. Earth and 90 degrees don't come into this at all.

At any given
instant and location the summation of both conductors with respect to
each other is equal to the magnitude it would be on the inner
conductor on the unbalanced (coax) with respect to ground (shield).
Since magnitude of the V on each conductor of the balanced line are
equal and opposite in phase, the term "balanced" is appropriate. Same
with I.

Yes... but this definition of "balanced" also REQUIRES that the
common-mode current is zero. The two are locked together, so if
"balance" is your aim, the practical way to achieve it is to force the
common-mode current to a lower value.

We have some direct leverage on common-mode current, because it's a
real, measurable thing. But "balance" is only a concept, and there isn't
any *direct* leverage that we can apply to it.

So even though a "common-mode choke" and a "current balun" are two
different names for the same physical device, it does make a difference
which name you choose. Think "common-mode choke", and you can see the
levers that will make your antenna/feedline system perform the way you
want it to. Think "balun", and all you see is a label that covers those
levers up.


[...]
But think of your dipole as a balanced transmission line. That's what
it is, with a lot of loss (into radiation resistance).
You WANT common mode on THAT that lossy transmission line and you do
not want it filtered away.

Again, that is all so misconceived - at every turn, it clashes with
obvious, measurable physical reality; or else it contradicts itself.
I'm sorry, but you really do need to do a clean wipe and start again
with a good textbook.


--

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

"Ian Jackson" wrote in message
...
In message , John Smith
writes
Ian Jackson wrote:

John,
You have a typo in the slogan after your 'signature'. [At least, I
presume it's a typo.] It's annoying me intensely. Please would you
correct it.

Ian:

How about just disabling it, that was really enough of that anyway ...
;-)

Regards,
JS

No, I like the sentiment expressed. It's just the typo that is getting
to me!!!
--
Ian

So who makes up the slogans for the dems? Is it some kind of secret code?
Except for the fact that they hold peoples jobs and freedoms with an iron
fist and treat us all like school children, the candidates don't seem to do
anything of merit. Is it really all about blaming the other guy about what
your people are getting away with under their watch?

JB wrote:

...
So who makes up the slogans for the dems? Is it some kind of secret code?
Except for the fact that they hold peoples jobs and freedoms with an iron
fist and treat us all like school children, the candidates don't seem to do
anything of merit. Is it really all about blaming the other guy about what
your people are getting away with under their watch?



Do you really think the "men" behind the curtain(s) pulling the puppets
strings are from different groups? i.e., Republicrats vs. Democans.

Fat chance; Me thinks the game is fixed. However, the "Laws of
Illusion(s)" dictates it is only that which is perceived which counts ...

Regards,
JS

"Richard Clark" wrote in message
...
On Sat, 30 Aug 2008 21:03:45 GMT, "JB" wrote:

I simply prefer not to attract tons of V-agra spam. These newsgroups are
seriously mined and my actual e-mail address associated with this login
is
set to dump all mail because of that.

I have transmited in the clear here for the past 13 years.

Since May, I have received all of 2 spams - from the son of Charles
Taylor in Africa. The amount of spam that predated that is of like
proportion.

I've heard the same arguments from kids who do drugs or refuse to wear seat
belts.
"It won't happen to me". I wouldn't want to lose my e-mail account or my
callsign to a spoof binge.

The truth speaks for itself. You can come up with any excuse to deny it.

In those same 13 years I've often heard the same excuse you are using.

Anyone who is willing to quote the Bible, but refusing to testify is
obviously of little faith - a Xerox can do as much and "anonymous"
sources lean on that copy button freely without conviction.

73's
Richard Clark, KB7QHC

What do you want? A new book of the Bible? How's this for testimony -
I must be a thorn in the side of the devil or he wouldn't have been trying
to take me and my dad out all our lives. The Lord has delivered me over and
over and even set a table before me in front of my enemies. My dad now
rests in Jesus. My rest is yet to come. Maybe if I was a poet or a
songwriter I could add to the Psalms but I leave that to others with that
gift.

On Mon, 01 Sep 2008 15:11:47 GMT, "JB" wrote:

How's this for testimony

It isn't.

73's
Richard Clark, KB7QHC

"John Smith" wrote in message
...
JB wrote:

...
So who makes up the slogans for the dems? Is it some kind of secret
code?
Except for the fact that they hold peoples jobs and freedoms with an
iron
fist and treat us all like school children, the candidates don't seem to
do
anything of merit. Is it really all about blaming the other guy about
what
your people are getting away with under their watch?



Do you really think the "men" behind the curtain(s) pulling the puppets
strings are from different groups? i.e., Republicrats vs. Democans.

Fat chance; Me thinks the game is fixed. However, the "Laws of
Illusion(s)" dictates it is only that which is perceived which counts ...

Regards,
JS

I have often considered the Good Cop Bad Cop theory of the Rep - Dem scam on
the people. The fact that they go to the same parties and get-togethers
means they share the same thoughts. It doesn't mean there is a conspiracy
per-se. Think of it as one big party that everyone has to go to or be left
out, and even though everyone goes kissy-kissy, they are knifing in the
back. Distrust and polite smack is all around. Rather than conspiracy
though, there is convergence in thought on matters brought to light to be
wrestled over while more important matters are forgotten for the moment. We
the People get left behind.

Who do you vote for though... Obama has been hanging around the Rev. kill
whitey bunch for too long. No telling what disease he might have picked up.
There also seems to be some overcompensation, the way he so desperately
needs to validate himself with every group that he forgets who he is from
day to day. By the same token, what damage was done to McCain while being
thrashed in the POW camp. But he does seem to have tolerance and compassion
even though he sticks to his guns.

The fact we are narrowed to two parties smacks of some kind of collusion.
Especially in the light of certain travesties of the Dems that the Reps are
curiously silent on. Perhaps McCain is so attractive due to the fact he has
proven to be less of a party lapdog.

"Richard Clark" wrote in message
...
On Mon, 01 Sep 2008 15:11:47 GMT, "JB" wrote:

How's this for testimony

It isn't.

73's
Richard Clark, KB7QHC

Oh it's you again. You don't seem to do much other than poke the fire.

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"?



An ideal common-mode choke would dissipate zero heat energy, and a
successful real-life choke will dissipate only a tiny fraction of the
available RF power.

CM choke is a filter, not an energy transfer device. Do you have any
formal education in electrical engineering?


When you insert a common-mode choke, you are inserting a large impedance
into the pathway of the common-mode current. *The RF current
distribution throughout the entire antenna/feedline/ground system will
adjust to take account of this new impedance. As a result, most of the
common-mode current will be DIVERTED away from its former pathway, and
will flow instead in the antenna.

Whew. You sort of describe a balun except that the balun is an
impedance matching device, in this discussion 1:1.
What new impedance does your 1:1 balun change you transmission line
and antenna feedpoint to ;-)


The details are complicated, but the concept that the choke DIVERTS
common-mode current away from the feedline is reasonably accurate. (By
contrast, the concept that it "turns unwanted RF current into heat" is
just plain wrong.)

Strawman. I didn't say that! RF current or voltage at the antenna is
not unwanted. You are the one who says you use a common choke choke at
your antenna feedpoint, not I.


If the choke is doing its job, the new value of common-mode current
(I_cm) flowing through the choke will be much less than the previous
value. The power dissipation in the choke will then be (I_cm)-squared x
R, where R is the resistive part of the choke's impedance at that
frequency. Note that I_cm is the small amount of common-mode current
that remains *after* having inserted the choke - not the value before!
The practical outcome is that a higher choke impedance will give *lower*
heat dissipation in the choke itself.

I cannot believe you are serious. You actually insert a choke at your
antenna input? I insert an efficient balun ;-)
Have you ever thought that there might be a reason for people
differentiating the use of a balun by use of the term "balun"?
There is a reason. On paper, it looks the same as a balun. In
operation, the CM choke presents a high impedance to
unwanted RF where the balun presents a MATCHED impedance to
intentional RF.


If a common-mode choke is getting hot, it isn't working.

It is working quite well if the filtered RF is dissipating in the
intentionally lossy core. (Such as powdered iorn).


Unfortunately
there are many chokes that don't have a high enough impedance to handle
the full range of real-life situations. If a choke is not able to
suppress the common-mode current to a low enough value, then in some
situations it will get hot *[1, 2]. *But PLEASE don't imagine that is
how common-mode chokes are intended to work!

[1] *http://www.w8ji.com/Baluns/balun_test.htm

[2]http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf

Also see other pages and publications from the same authors.

A
balun is intended to change the feed from an unbalanced transmission
line to a balanced output, for example, for connection to a balanced
transmission line or to an antenna such as a dipole. With the balun,
we wany NO reduction in RF current flow.

What exactly do you mean by that?

Umm, we do not want to reduce power from the transceiver to the
antenna?


You do not want the balun to operate hot (ir to dissipate heat as you
do with a CM choke filter). You strive for 100% transfer of energy and
settle for the best
you can get. With a CM choke, you try to filter and dissipate unwanted
back-RF. Any back RF from your balun
should be converted to unbalanced transfer back to the source. You
reduce back-RF by matching impedances (which can also involve baluns
but not the 1:1 application discussed here). If you try to filter it
the unwanted back-RF, you will also end up filtering the forward
energy transfer. Of course, that would be an undersirable situation.

Sorry, but that is so confused I can't even begin to unpick it...

It sounds like you have reached the plateau of your ability to
understand RF and transmission lines. THAT is the reason for
you confusion. Sorry.


except
by pointing to "you try to filter and dissipate unwanted back-RF". In so
many different ways, that is NOT *what we're trying to do. Tug on that
loose strand, and the whole thing unravels.

Continue the metaphor. Tug on that loose strand and what do you
discover, thus unraveling what?



And also, what exactly do you mean by "balanced" in the context of a
feedline?

For a 2 conductor feedline, the V in each conductor is 180 degrees out
of phase with each other. Same with I.

Yes.

One conductor is +90 degrees
and the other is -90 degrees with respect to earth.

No. Earth and 90 degrees don't come into this at all.

Yes it does! This reveals a large part of your confusion. The shield
on the coax is at earth. Earth is always involved. Do you know that
you could connect an earthing point exactly half way down the
"balanced" winding of the balun and have no effect on the operation of
the balun? There is no reason to do that of course but it illustrates
what the balun does. The center portion of the balanced winding is an
isolated 'earth' connection (that does need to be isolated but it is).
One side is -90, center is 0 (earth) and the other side is +90. On the
unbalanced side, there is no phase shift of course; you only have 0
(shield) and inner conductor voltage/current.

At any given
instant and location the summation of both conductors with respect to
each other is equal to the magnitude it would be *on the inner
conductor on the unbalanced (coax) with respect to ground (shield).
Since magnitude of the V on each conductor of the balanced line are
equal and opposite in phase, the term "balanced" is appropriate. Same
with I.

Yes... but this definition of "balanced" also REQUIRES that the
common-mode current is zero.

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

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

JB wrote:

...
73's
Richard Clark, KB7QHC

Oh it's you again. You don't seem to do much other than poke the fire.



Give him a personality to "poke" (no gay pun intended! :-) ), things
will turn into a real riot then!

Regards,
JS

I was just wondering, "Could Jesus possibly have pointed ears like
spock?" 8-)

JB wrote:

...
I have often considered the Good Cop Bad Cop theory of the Rep - Dem scam on
the people. The fact that they go to the same parties and get-togethers
means they share the same thoughts. It doesn't mean there is a conspiracy
per-se. Think of it as one big party that everyone has to go to or be left
out, and even though everyone goes kissy-kissy, they are knifing in the
back. Distrust and polite smack is all around. Rather than conspiracy
though, there is convergence in thought on matters brought to light to be
wrestled over while more important matters are forgotten for the moment. We
the People get left behind.

Who do you vote for though... Obama has been hanging around the Rev. kill
whitey bunch for too long. No telling what disease he might have picked up.
There also seems to be some overcompensation, the way he so desperately
needs to validate himself with every group that he forgets who he is from
day to day. By the same token, what damage was done to McCain while being
thrashed in the POW camp. But he does seem to have tolerance and compassion
even though he sticks to his guns.

The fact we are narrowed to two parties smacks of some kind of collusion.
Especially in the light of certain travesties of the Dems that the Reps are
curiously silent on. Perhaps McCain is so attractive due to the fact he has
proven to be less of a party lapdog.


When Martin Luther King got them to promise, "OK, we are going to cut
you in on a piece of the pie ..." They suddenly kicked open the doors
on immigration from starving/impoverished 3rd world nations and added
the words, to the above, "NOW, grab yourself a piece of that pie!"

"That is 'IT', in a nutshell." However, there are whole books which
would could be written to fill in what the above doesn't mention.

Many have good reason to fear Obama. If he cuts in his friends,
relatives and people of his like color, ethnicity and background(s), we
are all in for "sharing a piece of our pie!" And, we all know it has to
happen, we were just hoping to put it off and let our children deal with
it (like deficit spending, where we have put off our bills for our
children to pay.)

Now, that is enough, I am done with this sub-off-topic-thread ... you
will excuse my leave ...

Regards,
JS
I was just wondering, "Could Jesus possibly have pointed ears like
spock?" 8-)