balun?

[Mark-T]

What is a balun, and what for?

How is it different than any other transformer?


Thanks,
Mark

 

[Michael A. Terrell]

What is a balun, and what for?

How is it different than any other transformer?

Thanks,
Mark

Balun = Balanced to Unbalanced. It is used to convert a balanced
line to single ended, or vice versa.

 

[Bob Myers]

What is a balun, and what for?

The answer in this case is in the name: a "balun" is a device
for converting between an unbalanced line and a balanced
load, or vice-versa. Hence, BALanced-to-UNbalanced
(transformer, although not all "baluns" are transformer-like
devices - you can make a balun for a given frequency from
the right length of transmission line, f'rinstance). Pretty common
in antenna/transmission line work.

How is it different than any other transformer?

For the transformer type, it's not, really, in the basic
theory of the thing - it's more in how it's connected, and
in practice that generally it is intended for high-frequency,
fairly broadband operation (very high, compared to power
transformers and the like).

Bob M.

 

[JeffM]

What is a balun, and what for?

Mark-T

The most common ones have 75 ohm coax on one end
and 300 ohm flat lead on the other.
..
..

How is it different than any other transformer?

US TV Channel 13 == 216 MHz
Channel 83 == 890 MHz

 

[Paul Burridge]

The answer in this case is in the name: a "balun" is a device
for converting between an unbalanced line and a balanced
load, or vice-versa. Hence, BALanced-to-UNbalanced
(transformer, although not all "baluns" are transformer-like
devices - you can make a balun for a given frequency from
the right length of transmission line, f'rinstance). Pretty common
in antenna/transmission line work.


For the transformer type, it's not, really, in the basic
theory of the thing - it's more in how it's connected, and
in practice that generally it is intended for high-frequency,
fairly broadband operation (very high, compared to power
transformers and the like).

Indeed. A typical balun would appear as a dead-short to a mains
frequency signal.

 

[Michael A. Terrell]

Indeed. A typical balun would appear as a dead-short to a mains
frequency signal.

You've never seen a line isolation transformer?

 

[Mark-T]

The answer in this case is in the name: a "balun" is a device
for converting between an unbalanced line and a balanced
load, or vice-versa. Hence, BALanced-to-UNbalanced
(transformer, although not all "baluns" are transformer-like
devices - you can make a balun for a given frequency from
the right length of transmission line, f'rinstance). Pretty common
in antenna/transmission line work.


For the transformer type, it's not, really, in the basic
theory of the thing - it's more in how it's connected, and
in practice that generally it is intended for high-frequency,
fairly broadband operation (very high, compared to power
transformers and the like).

So the primary has one side grounded, while the secondary
goes to the inputs of a diff. amp, with center tap to ground?

Mark

 

[Bob Myers]

So the primary has one side grounded, while the secondary
goes to the inputs of a diff. amp, with center tap to ground?

Why assume a grounded center tap? Better to say that
the primary - or input side - has one end connected to the
"ground" or reference used for the unbalanced output of
whatever you're connecting to, and the output side is
connected to a balanced input - for instance, perhaps it
feeds a dipole antenna. No need for a "ground" at all
on the output side!

Bob M.