A current balun (as described by W2DU in his book ''Reflexions''), put at
the center of a dipole, prevents HF current from flowing in the outer shield
of the coax. This is due to the high impedance caused by the ferrite rings.
Now, if instead, I put a voltage balun, what should prevent the current from
flowing in the outer shield of the coax? Am I missing something?

Thanks for helping.

Chris

W2DU's device is not a balun. It has no ratio - it is just a choke.
It behaves in the same way as a single bifilar winding on a ferrite
rod, or on a ring.

But a choke does not necessarily prevent longitudinal standing-wave
currents on the line. It merely shifts standing waves to other
positions along the line.

If a choke is located at a current minimum it may serve no useful
purpose at that operating frequency.

A true balun transformer, whatever its ratio, by itself provides no
obstruction to longitudinal currents. There can be a direct connection
between the line and antenna.
----
Reg, G4FGQ.

On Thu, 28 Apr 2005 14:19:18 +0000 (UTC), after apparently consuming a
750 ml bottle of California red, "Reg Edwards"
wrote:

W2DU's device is not a balun. It has no ratio - it is just a choke.
It behaves in the same way as a single bifilar winding on a ferrite
rod, or on a ring.

Wherever did you get the idea that a balun "must have a ratio?"

"Balun" is a contraction of 'Bal'anced to 'Un'balanced. Walt's device
certainly fulfills this function.

[remaining bafflegab snipped]

Balanced to Unbalanced WHAT ?

"Balun" is a contraction of "Balanced to Unbalanced "TRANSFORMER".

What is the transformation ratio of the W2DU "balun" and other devices
which serve a similar purpose? Between which pair of impedances does
it match?

If YOU cannot provide answers then there are many old-wives who can.

There is a program named BALCHOKE available free from my website.

I have no wish to participate in futile arguments about the meaning of
words. They can drive one to drink
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

===================================

"Wes Stewart" wrote:

W2DU's device is not a balun. It has no ratio - it is just a
choke.
It behaves in the same way as a single bifilar winding on a ferrite
rod, or on a ring.

Wherever did you get the idea that a balun "must have a ratio?"

"Balun" is a contraction of 'Bal'anced to 'Un'balanced. Walt's
device
certainly fulfills this function.

[remaining bafflegab snipped]

Reg Edwards wrote:
What is the transformation ratio of the W2DU "balun" and other devices
which serve a similar purpose? Between which pair of impedances does
it match?

Resorting to passive voice - The W2DU choke is considered to
be a 1:1 balun. Each bead is considered to be one turn. If
one mounts the beads on a piece of 50 ohm coax, it becomes
a 50 ohm balanced to 50 ohm unbalanced balun. With 50 ohms
on both sides of the balun, the Z0 of the transmission line
used should be SQRT(50*50)=50 ohms.
--
73, Cecil, http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

You are correct on this point, it is actually an "UnUn."
(UNbalanced-to-UNbalanced--don't confuse this with a child's pronouncing of
"onion.") grin

Regards,
John

On Thu, 28 Apr 2005 18:03:40 +0000 (UTC), "Reg Edwards"
wrote:

What is the transformation ratio of the W2DU "balun"

1:1

Reg Edwards wrote:

Balanced to Unbalanced WHAT ?

Isn't that rather like asking Modulated to Demodulated WHAT?

ac6xg

"Reg Edwards" wrote -

Balanced to Unbalanced WHAT ?

"Balun" is a contraction of "Balanced to Unbalanced "TRANSFORMER".

What is the transformation ratio of the W2DU "balun" and other
devices
which serve a similar purpose? Between which pair of impedances
does
it provide a match?

If YOU cannot provide answers then there are many old-wives who can.

There is a program named BALCHOKE available free from my website.

=====================================

To all and sundry,

My prediction about old-wives was correct.

Anybody who provided a transformation ratio or mentioned matched
impedances can consider him or herself to be an Old Wife.

It would be a waste of time for me to explain to Old Wives how the
uncertain impedance and length of line on the choke, combined with the
unknown impedances of its supposed terminations, actually works.

The impedance transformation ratio is entirely INDETERMINATE.

But it doesn't matter two hoots provided the length of line on the
choke is within certain limits. Only the choking action on
longitudinal currents matters.

smile please
----
Reg, G4FGQ

Reg Edwards wrote:
"Reg Edwards" wrote -


Balanced to Unbalanced WHAT ?

"Balun" is a contraction of "Balanced to Unbalanced "TRANSFORMER".

What is the transformation ratio of the W2DU "balun" and other

devices

which serve a similar purpose? Between which pair of impedances

does

it provide a match?

If YOU cannot provide answers then there are many old-wives who can.

There is a program named BALCHOKE available free from my website.


=====================================

To all and sundry,

My prediction about old-wives was correct.

Anybody who provided a transformation ratio or mentioned matched
impedances can consider him or herself to be an Old Wife.

It would be a waste of time for me to explain to Old Wives how the
uncertain impedance and length of line on the choke, combined with the
unknown impedances of its supposed terminations, actually works.

The impedance transformation ratio is entirely INDETERMINATE.

But it doesn't matter two hoots provided the length of line on the
choke is within certain limits. Only the choking action on
longitudinal currents matters.

smile please
----
Reg, G4FGQ



What's a "longitudinal current?" Is there a "latitudinal current" for
it to be opposed to?
73,
Tom Donaly, KA6RUH