I have dug out of my box an old 1:1 balun I wound several years ago,
possibly to a design in to the ARRL Handbook or the Antenna Handbook neither
of which I sill have. This was wound with the main winding bifilar on one
half of the (BIG) core and the third 'magnetising' winding on the opposite
side of the core.

I can find many balun designs using just the bifilar pair and some with a
third winding trifilar with the first two but can't find reference to
separating the third winding. Can anyone shed any light on why I might have
done it this way. I'm sure it was recomended somewhere but my memory is
fading.......

I'm just curious to know why it was done as on a quick test with antenna
analyzer and 50 ohm carbon resistor as a load it seems to work well from
below 3 to 30 MHz. An oscilloscope shows the output to be well balanced.

73 de Dick G4BBH

On Sat, 13 Jan 2007 22:03:04 -0000, "ferrymanr"
wrote:
[snip]
.......quick test with antenna
analyzer and 50 ohm carbon resistor as a load it seems to work well from
below 3 to 30 MHz. An oscilloscope shows the output to be well balanced.

I would be far more concerned as to what its common mode impedance is.
From what you describe it sounds like a voltage balun and those
generally have a poor common (blocking) mode impedance.

Danny, K6MHE

"Danny Richardson" wrote in message
...

I would be far more concerned as to what its common mode impedance is.
From what you describe it sounds like a voltage balun and those
generally have a poor common (blocking) mode impedance.

Danny, K6MHE


I would guess that you are right Danny and this is a voltage balun. I dug
it out as I have recently moved to a flat in the centre of town 100 yards
from a large telephone exchange and surrounded by noise sources. My old
trusty vertical is giving me so much noise here that I want to put up a
balanced antenna in the hope that this will reduce the interference. To
minimise this noise I need a well balanced system. I already have coax up
to the roof and balanced line would be difficult to route so am planning to
fit a balun either at the dipole centre or a few feet below with a short
balanced feed. I dug this balun out as it looked like it would give good
balance. I have another (current) balun which has a simpler bifilar
winding. I'm not sure which will be best for my application. Incidentally
I only run QRP so efficiency is a major factor. I also considered a folded
dipole using 600 ohm line as that would be less prone to static noise but
would then have to look at a 4:1 design.

73 de Dick G4BBH

Dick wrote:
Danny Richardson wrote:

I would be far more concerned as to what its common mode impedance is.
From what you describe it sounds like a voltage balun and those
generally have a poor common (blocking) mode impedance.

Danny, K6MHE


I would guess that you are right Danny and this is a voltage balun. I dug
it out as I have recently moved to a flat in the centre of town 100 yards
from a large telephone exchange and surrounded by noise sources. My old
trusty vertical is giving me so much noise here that I want to put up a
balanced antenna in the hope that this will reduce the interference. To
minimise this noise I need a well balanced system. I already have coax up
to the roof and balanced line would be difficult to route so am planning
to
fit a balun either at the dipole centre or a few feet below with a short
balanced feed. I dug this balun out as it looked like it would give good
balance. I have another (current) balun which has a simpler bifilar
winding. I'm not sure which will be best for my application.
Incidentally
I only run QRP so efficiency is a major factor. I also considered a
folded
dipole using 600 ohm line as that would be less prone to static noise but
would then have to look at a 4:1 design.

73 de Dick G4BBH


Hi Dick,

Have you considered a simple "Ugly Balun" (http://tinyurl.com/uvnt3)? It is
nothing more than the end of your feedline coiled up, at the antenna
feedpoint. Another better approach is a stack of ferrite cores at the
feedpoint. These are commecially available, though you can easily make your
own. I found some good reading he http://tinyurl.com/uzvkh.

A folded dipole will look like 300 ohms. A 4:1 balun will present 75 ohms to
the feedline; you'd need a 6:1 ratio in order to see 50 ohms.
That aside, a multiwire dipole (such as a folded dipole) will exhibit
greater bandwidth than a single-wire dipole. My experience says that (at
80m) you'll see ~ 100 KHz for each set of wires, whether they're in the form
of fan dipole, cage dipole, or folded dipole. I prefer a cage dipole over
the other two:
1 - same number of supports as with a single-wire dipole or folded-dipole
2 - matches directly into low-Z coaxial cable
I use one (in inverted-vee form during Field Day
(http://tinyurl.com/ybbsba)... approximately 400 KHz bandwidth, and uses
easy-to-make spreaders.

Vy 73 ob,
Bryan WA7PRC

The third winding converts a current balun into a voltage balun. If the
antenna is completely symmetrical with respect to ground, the third
winding carries no current and does nothing. If the antenna isn't
symmetrical, the third winding forces an imbalance in current between
the antenna halves. The difference current flows on the transmission
line as a common mode current. So at best it does nothing, at worst it
causes the very problem a balun is intended to prevent.

There's more about this at http://eznec.com/Amateur/Articles/Baluns.pdf.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...

There's more about this at http://eznec.com/Amateur/Articles/Baluns.pdf.

Roy Lewallen, W7EL

Thanks for the link Roy. A very useful document. Have also printed a copy
to place in the local club archives.

73 de Dick G4BBH

ferrymanr wrote:
"Roy Lewallen" wrote in message
...
There's more about this at http://eznec.com/Amateur/Articles/Baluns.pdf.

Roy Lewallen, W7EL

Thanks for the link Roy. A very useful document. Have also printed a copy
to place in the local club archives.

73 de Dick G4BBH

Please respect the copyright.

Roy Lewallen, W7EL

"ferrymanr" wrote in message
...

I would guess that you are right Danny and this is a voltage balun. I dug
it out as I have recently moved to a flat in the centre of town 100 yards
from a large telephone exchange and surrounded by noise sources. My old
trusty vertical is giving me so much noise here that I want to put up a
balanced antenna in the hope that this will reduce the interference. To
minimise this noise I need a well balanced system. I already have coax up
to the roof and balanced line would be difficult to route so am planning
to fit a balun either at the dipole centre or a few feet below with a
short balanced feed. I dug this balun out as it looked like it would give
good balance. I have another (current) balun which has a simpler bifilar
winding. I'm not sure which will be best for my application.
Incidentally I only run QRP so efficiency is a major factor. I also
considered a folded dipole using 600 ohm line as that would be less prone
to static noise but would then have to look at a 4:1 design.

73 de Dick G4BBH


Hi Dick,
You might want to try a horizontal loop antenna, they are very quite with
respect to QRM.

http://www.bloomington.in.us/~wh2t/loop.html

If you need a 4:1 balun :
http://www.bloomington.in.us/~wh2t/balun.html

7, Ace - WH2T

"Dr.Ace" wrote in message
...

Hi Dick,
You might want to try a horizontal loop antenna, they are very quite
with respect to QRM.

http://www.bloomington.in.us/~wh2t/loop.html

If you need a 4:1 balun :
http://www.bloomington.in.us/~wh2t/balun.html

7, Ace - WH2T



TYPO Correction : quite should read quiet .