In message , John Smith
writes
JB wrote:
... The notion that
apes transitioned into humans is more farfetched than if we were evolved
from ferns or fruit flies, if we were to compare the DNA structures. Today
we have youth wearing "natural selection" T-shirts going on shooting sprees
and random gang killings for tatoos so don't tell me about evolution.
...

If one were to tear apart a mud hut, and then a state-of-the-art
building, he/she would only find the basic building blocks are more
similar then dissimilar ... most likely, 99%+ of the elements in the
state of the art building can also be found in the mud-hut ... I see no
reason why someone should expect different in the basic building blocks
of life.

First there is a prototype, then improved designs, and at some point in
the future, or far-far-future, a finished design (maybe.)

We are all looking at the same "evidence" alright, the crux of the
matter is in the interpretation(s.)

Regards,
JS
Half-a-Brain-McCain'n Insane; So Lawdy Mama, It Looks Like Obama!

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

On Sun, 31 Aug 2008 19:08:36 +0100, 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.

Hi Ian,

Are you referring to the minstrel baiting term? It's bad enough to
tolerate this anonymous carnival of religious cliches with their
dialog of obscene pandering.

73's
Richard Clark, KB7QHC

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
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?

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

I agree that the effect is
the same, semantically, ie one side effect of the use of a balun is
less CM interference from coming down a balanced feedline but it is
there for a different reason.

Not in my station. My motivation for using common-mode chokes is
*specifically* to control any incoming and outgoing interference that
may be caused by common-mode currents on the feedline.

When the common-mode component of the feedline is reduced, it will also
be accompanied by an improvement in "balance" on the antenna, because
the two things go together (or at least, they do for some definitions of
that word). But "balance" is never my primary goal because I don't find
the concept helpful, either when deciding what to do next or when
evaluating the results.



--

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

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

JB wrote:

...
I lost your context then. The only thing in common between the skyscraper
and mud hut is that they have a maker and some plan. Maybe some wood. If
you are talking Chemistry, then you are getting specific and I doubt they
use the same mud formula in the skyscraper anywhere but in the flower pots.
...

Iron is iron, whether in a pure form, alloys, rust or other ferric
compounds. Silicon is silicon, whether in a window pane, silicon oxide,
or some other compound of silicon. Calcium is calcium, whether in
limestone, cement, earth, or other calcium compounds, etc., etc. ...

Back when I was in college, someone did some computations of how the
body of Plato would have decayed and been dispersed throughout the world
in the thousands of years since his death. They arrived at the
conclusion that everyone on the planet would have at least 6 molecules
from Platos' body in their own bodies (mostly water molecules since that
is the major component of the human body) ... I cannot verify the
accuracy of those computations--however, you get the drift--I am part
Plato! grin

Regards,
JS

Richard Clark wrote:

...
Hi Ian,

Are you referring to the minstrel baiting term? It's bad enough to
tolerate this anonymous carnival of religious cliches with their
dialog of obscene pandering.

73's
Richard Clark, KB7QHC

Has someone snuck into this forum and now lies under the bleachers
bellowing for help? I thought I heard some inane and insane rantings
from an individual out of his mind with pain!

Reminds me of that poor b*st*ard which used to go around mumbling quotes
from Shakespeare in reply to technical discussions ... at least he is
gone for the moment, or so it might seem. :-)

Regards,
JS

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

Richard Clark wrote:

...
Hi Ian,

Are you referring to the minstrel baiting term? It's bad enough to
tolerate this anonymous carnival of religious cliches with their
dialog of obscene pandering.

73's
Richard Clark, KB7QHC

Hmmm, playing, "I am taking the high road game, huh?

Ok. Well, here is my favorite version:

Fee-fi-fo-fum
I smell the blood of an Englishman.
Be he alive or be he dead
I'll grind his bones to make my bread. -- "Jack the Giant Killer."

Now, one sure to be your fav:

"Child Roland to the dark tower came,
His word was still, Fie, foh, and fum,
I smell the blood of a British man." -- Shakespeare, "King Lear."

And, for those finding neither to their liking:

"O, tis a precious apothegmatical Pedant, who will find matter enough to
dilate a whole day of the first invention of Fy, fa, fum, I smell the
blood of an English-man". -- Thomas Nashe, "Have with you to
Saffron-walden."

Ahhh, remember the good-ole-days when you could write this
gooble-de-gook for yourself? A burden which has now befell my
shoulders--I only thank God they are broad (my shoulders of course, not
the women!) :-(

However, Shakespeare does seem to befit some as more appropiate
"trolling lines" than myself ...

Regards,
JS

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..


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.


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



I agree that the effect is
the same, semantically, ie one side effect of the use of a balun is
less CM interference from coming down a balanced feedline but it is
there for a different reason.

Not in my station. My motivation for using common-mode chokes is
*specifically* to control any incoming and outgoing interference that
may be caused by common-mode currents on the feedline.

Of course. But it is not due to filtering unwanted RF, it is due to
the conversion of balancing your energy so
that the coax properly acts as a shielded unbalanced line with no
energy in the shield and all energy in the inner conductor
(assuming perfect conditions). Your dipole will try to balance when
fed as a dipole directly from a coax.. Without the balun, any
reflected energy will
partially come down the shield to ground causing interference. The
balun simply unbalances the reflected energy, if any, to that it all
returns through
the inner conductor eliminating RFI if the radio and the shield are
properly earthed.


When the common-mode component of the feedline is reduced, it will also
be accompanied by an improvement in "balance" on the antenna, because
the two things go together (or at least, they do for some definitions of
that word).

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.

But "balance" is never my primary goal because I don't find
the concept helpful, either when deciding what to do next or when
evaluating the results.

I say "balanced" is your primary goal though you do not realize it.
You want to balance the energy propagation in your dipole "lossy
transmission line", when feeding it with an unbalanced coax. The balun
should accomplish that. Anything reflected is not good but at least it
is reflected "unbalanced" inside the grounded shield causing less EMI.

wrote in news:c2a78f6b-eded-4547-ae32-bc8ccd60e186
@m73g2000hsh.googlegroups.com:

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

I suggest that a reasonable definition of a balun is any device that
facilitates or assists transition from unbalanced to balanced mode of
operation. That definition permits a wide range of devices that may have
characteristics suited to specific applications.

(Keeping in mind that an unbalanced feedline is often not ideal in
application, ie one where common mode current is exactly half of the
differential current, and a two wire open line is often not ideal in
application, ie where common mode current is zero.)

Most people naturally think of balance in terms of voltages wrt some common
reference, eg ground. It is equally legitimate, and often more appropriate
to the antenna / feedline scenario, to seek balance in terms of current, ie
to minimise common mode current.

Owen