Baluns?
 

Owen Duffy wrote:

...
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.
...
Owen

Baluns and Ununs use a transmission line mode to accomplish their tasks
.... anything else is just a RF xfrmr ...

However, there are the 180 degree hybrid baluns ...

Regards,
JS

Baluns?
 

John Smith wrote:

However, this URL:

http://www.n0ss.net/qrp_4-1_guanella-type_balun.pdf

in the include pick 4-1_schematic.jpg, in the URL, contains a "blurb" on
how to move a single core design on to two cores.

Did you mean a two core design onto one core?

Here is an analysis of the single core version:
http://www.vk1od.net/balun/gsc/index.htm .

Guanella did not show the 4:1 balun on a shared magnetic circuit, and it
is an error on the part of those who think that the two independent TLTs
in Guanella's circuit can be coupled without changing the behaviour
significantly (basically, ruining it).

Owen

Baluns?
 

Here is a URL for design/implementation of "non-standard"
baluns/transformers, but of a highly useable and desirable nature--or,
Dr. Sevick strikes again!:

http://www.highfrequencyelectronics....104_Sevick.pdf

Fig. 6(A) is very interesting. A 5-winding, 1:1.56 bootstrap
transformer which provides 50/75 ohm connections/substitutions. Perfect
for allowing one to use 75 ohm "junk" (or found in dumpsters) tv coax in
place of more expensive 50 ohm coax.

I have made good use of this since I have thousands of feet of NEW 75
ohm coax I purchased from a scrap dealer for next-to-nothing! A lot of
large dia coax and hard-line mixed in!

Regards,
JS
A little mismatch isn't such a problem. At least if you can get the loss
down. I wouldn't even worry about it, the internal tuner would make short
work of that. Look out for water damage on that stuff though. Especially
the Aluminum braid/foil shield stuff like LMR. Even a little bit of
moisture percolates all through the braid.and turns it into aluminum oxide
powder and extremely noisy with power on it. It could look brand new and
you would keep cutting it back, then find a foot of new braid but keep
cutting and its back to chalk. We would routinely assume it bad and throw
it away. At least with the Hardline, you can sweep it and put some power to
it to check the loss Only hardline allowed on towers.

Baluns?
 

JB wrote:

...
A little mismatch isn't such a problem. At least if you can get the loss
down. I wouldn't even worry about it, the internal tuner would make short
work of that. Look out for water damage on that stuff though. Especially
the Aluminum braid/foil shield stuff like LMR. Even a little bit of
moisture percolates all through the braid.and turns it into aluminum oxide
powder and extremely noisy with power on it. It could look brand new and
you would keep cutting it back, then find a foot of new braid but keep
cutting and its back to chalk. We would routinely assume it bad and throw
it away. At least with the Hardline, you can sweep it and put some power to
it to check the loss Only hardline allowed on towers.


Since it was on spools, and dusty, had no concern with that. LOL

Regards,
JS
--
It is like a nightmare where the public servants are people which the
police are supposed to protect you from!

Baluns?
 

Owen wrote:

...
Did you mean a two core design onto one core?

Here is an analysis of the single core version:
http://www.vk1od.net/balun/gsc/index.htm .

Guanella did not show the 4:1 balun on a shared magnetic circuit, and it
is an error on the part of those who think that the two independent TLTs
in Guanella's circuit can be coupled without changing the behaviour
significantly (basically, ruining it).

Owen

Let's cut the crap, currents in one winding which cause lines of force
in the toroid/ferrite-core, should only assist the lines of force
generated in the core by the other winding on the opposite side of the
core--in the single core model of the guanella balun--composed of two
1:1s in a 1:4 configuration (or guanella TLT, since you seem to prefer
acronyms.) At least TLT get the transmission line requirement out in
the open ...

Since toroids naturally demonstrate "economy of loss" in the magnetic
lines of force within their structure, few, if any, lines of force would
be shared between two separate cores, stacked.

Now, wasn't it Einstein who recommended that things only be made as
complex as necessary and not one iota more?--Or, watch out for the gray
haired man who keeps attempting to sneak behind the curtains in this
train ride though Oz--and KEEP HIM AWAY FROM THE LEVERS! ;-P

Regards,
JS

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

Baluns?
 

On Sep 1, 9:52*pm, Owen Duffy wrote:
wrote in news:6f4f9e36-af26-4f1b-9244-383494f77b26
@c58g2000hsc.googlegroups.com:



On Sep 1, 3:25*pm, Cecil Moore wrote:
wrote:
...
Actually, 1000 ohms is pretty liberal. For instance, on
15m, the G5RV coax sees 36+j230 ohms or about 233 ohms.
The balun needs to be 10x that value or 2330 ohms.
--
73, Cecil *http://www.w5dxp.com

Why not 500 ohms, assuming a 50 ohm source and transmission line?

The common mode impedance of the balun acts in the common mode
transmission line (which is mutually coupled to the nominal radiator).

How is the differential mode transmission line characteristic impedance
relevant to the determination of common mode current in the antenna
system scenario described?

Owen

For a balanced transmission line, the characteristic impedance is not
expressed in differential mode terms, it IS common mode so I do
not know why you ask about differential mode characteristic impedance.
I never mentioned it. The characteristic impedance of a ladder line
for example
might be expressed as 600 ohms. That 600 ohms assumes common mode
conduction, as charateristically transmitted in a balanced line,
Differential mode impedance is assumed for un balanced transmission
line conditions.

Baluns?
 

On Sep 2, 7:26*am, Cecil Moore wrote:
wrote:
Yes and I have to partially take back what I said; a balun CAN double
as a CM "choke" and a CM choke can double as a balun. If
one wishes to balance an unbalanced line with a CM choke, then the
impedance of the CM choke must match the source and the load, which
makes the CM choke a balun and no longer a choke :-)

Actually, a balun without a large choking impedance
is not very useful for ham antenna system applications.
The method that a W2DU balun uses to balance currents
at a dipole feedpoint *IS* nothing more than a large
choking impedance which discourages common-mode current
from flowing through the higher-the-better impedance.
I usually refer to the W2DU balun as a choke-balun.
--
73, Cecil *http://www.w5dxp.com

I disagree. There is no choking, there is merely a polarity and phase
shift between the "primary" and "secondary" of the 1:1 balun
"transformer".

The best way I can easily express this is to consider a 1:1 240V 60 Hz
isolation transformer (yes, the balun acts theoretically in the same
manner). At the unbalanced input you connect 240V on one terminal and
earthed neutral on the other terminal. Now consider the isolated
secondary each feeding an equal resistive load to the center tap of
the secondary (analagous to radiation resistance). Across each load
we see 120V, 180 degrees out of phase. This is a balanced
transmission. Correct, this is not RF but it illustrates what the
balun is supposed to be doing. There is NO choking function at all if
it is working properly. There cannot be a choke when impedances are
matched, only when they are significantly mismatched.

Baluns?
 

On Sep 2, 7:51*am, Cecil Moore wrote:
wrote:
On Sep 1, 3:25 pm, Cecil Moore wrote:
Actually, 1000 ohms is pretty liberal. For instance, on
15m, the G5RV coax sees 36+j230 ohms or about 233 ohms.
The balun needs to be 10x that value or 2330 ohms.

Why not 500 ohms, assuming a 50 ohm source and transmission line?

Be the current making a choice of paths at a junction.
How much of you would flow through 500 ohms and how much
would flow through 233 ohms? (If 500 ohms is the total
impedance seen by the shield current looking back toward
the source, about 1/3 of the current would flow back
through the 500 ohms down the coax.)

http://eznec.com/Amateur/Articles/Baluns.pdf
--
73, Cecil *http://www.w5dxp.com

I got confused as to whether we were talking "choke" or "balun". For
the balun, you want to be as close to 50 ohms as possible. Actually
233 ohms is not that bad. 1K would be really bad and illustrate that
the balun is not working well. It 233 ohms, it is sort of OK,
especially with a tuner, which you use with a G5RV anyway, along with
the ugly balun. In priciople, the frequency works OK for my G5RV/ugly
balun system.

By the way, I have seen so many articles about baluns written by other
hams and they tend to repeat the same mistakes and assumptions. Most
hams do not understand how a balun works. Some even think you do not
need a balun if the antenna is at resonance which is totally untrue.
Anytime you feed a dipole directly with an unbalanced coax, the
balanced dipole "load" forces current down your ground shield and into
your radio and makes your radio part of your transmitting antenna.
Inserting a balun does not "choke" the current in the shield, it
merely shifts the output phases so that the current (voltage) is
directed towards the dipole at all times (see my other post in this
thread).

Baluns?
 

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.

Baluns?