balun spec depending on coax impedance
 

Dear all,

Usualy, people use 9:1 balun to connect a wire or dipole antenna to a 50 ohm coax.

If I use a basic TV coax (75 ohms) I suspect I will need a 6:1 balun instead. If
so, how many turns of wire should I use for primary and secondary windings ?

I don't know the impendance of the antenna connection of my radios (ATS 909 +
ICF SW100), so I intend to give a try with the coax I have in hand.

Thanks in advance for your help,

Charly

balun spec depending on coax impedance
 

Charly wrote:

Dear all,

Usualy, people use 9:1 balun to connect a wire or dipole antenna to a 50 ohm coax.

If I use a basic TV coax (75 ohms) I suspect I will need a 6:1 balun instead. If
so, how many turns of wire should I use for primary and secondary windings ?

I don't know the impendance of the antenna connection of my radios (ATS 909 +
ICF SW100), so I intend to give a try with the coax I have in hand.

http://www.dxing.info/equipment/impe...ing_bryant.pdf

http://members.aol.com/DXerCapeCod/z_transformers.pdf

dxAce
Michigan
USA

balun spec depending on coax impedance
 

dxAce wrote:

http://www.dxing.info/equipment/impe...ing_bryant.pdf

http://members.aol.com/DXerCapeCod/z_transformers.pdf

Good afternoon,

Yes, I have those one on my PC already... I think I have found most of the
articles dedicated on that topic.

But since I don't know exactly what is my toroïd material and constant values
for computation (I got my toroïd from a broken power supply) I was wondering
wether there was some "classical" windings spec...

Perhaps I will begin with a 1:1 balun (it should be the same number of turns for
both windings, right ?) and then start from that point to find a better
configuration.

Thanks anyway,

Charly

balun spec depending on coax impedance
 

Charly wrote:

dxAce wrote:

http://www.dxing.info/equipment/impe...ing_bryant.pdf

http://members.aol.com/DXerCapeCod/z_transformers.pdf

Good afternoon,

Yes, I have those one on my PC already... I think I have found most of the
articles dedicated on that topic.

But since I don't know exactly what is my toroïd material and constant values
for computation (I got my toroïd from a broken power supply) I was wondering
wether there was some "classical" windings spec...

Perhaps I will begin with a 1:1 balun (it should be the same number of turns for
both windings, right ?) and then start from that point to find a better
configuration.

Best bet would be to start off with a proper toroid, not one you know nothing about.

dxAce
Michigan
USA

balun spec depending on coax impedance
 

On Wed, 01 Mar 2006 18:44:49 +0100, Charly wrote:

dxAce wrote:

http://www.dxing.info/equipment/impe...ing_bryant.pdf

http://members.aol.com/DXerCapeCod/z_transformers.pdf

Good afternoon,

Yes, I have those one on my PC already... I think I have found most of the
articles dedicated on that topic.

But since I don't know exactly what is my toroïd material and constant values
for computation (I got my toroïd from a broken power supply) I was wondering
wether there was some "classical" windings spec...

Perhaps I will begin with a 1:1 balun (it should be the same number of turns for
both windings, right ?) and then start from that point to find a better
configuration.

Thanks anyway,

Charly

Why not just buy one of these and be done with it?

http://www.geocities.com/qrp_baluns/LMZ-50.html

balun spec depending on coax impedance
 

In article ,
Charly wrote:

Dear all,

Usualy, people use 9:1 balun to connect a wire or dipole antenna to a 50 ohm
coax.

If I use a basic TV coax (75 ohms) I suspect I will need a 6:1 balun instead.
If
so, how many turns of wire should I use for primary and secondary windings ?

I don't know the impendance of the antenna connection of my radios (ATS 909 +
ICF SW100), so I intend to give a try with the coax I have in hand.

Thanks in advance for your help,

Charly

The 75 ohm coax will be going into the radios 50 ohm input so that's
another problem.

What part of the power supply did the toroid come from? A toroid from
the EMI filter part of the supply would probably work well. If you have
the test equipment you could put one turn on the toroid and measure the
inductance. Also you could check the inductance over frequency to see
where that particular toroid will work.

Barring that use the minimum turns for a 9:1 anyway. Use a twisted or
overlapping method to wind the core. The antenna wire impedance will
change based on the wire diameter and height above ground so you need to
calculate that before you know what impedance ratio you would need to
begin with. Some people confuse the reactance of the wire with the wires
characteristic impedance, which is what you are trying to match. The
reactance of the wire will change with frequency.

--
Telamon
Ventura, California

balun spec depending on coax impedance
 

On Wed, 01 Mar 2006 18:20:29 +0100, Charly wrote:


Dear all,

Usualy, people use 9:1 balun to connect a wire or dipole antenna to a 50 ohm coax.

A resonant dipole, I believe, is about 72 ohms. Connecting it through
75 ohm TV coax to a 50 ohm receiver input should be a near ideal
match.

On non-resonant frequencies, the dipole will present different
matches. That shouldn't be a problem, though, just for listening on a
sensitive receiver.

A balun won't give you a decent match except on the single frequency
it is designed for. That's one problem you run into, putting a balun
on a multi-band or multi-frequency antenna.


If I use a basic TV coax (75 ohms) I suspect I will need a 6:1 balun instead. If
so, how many turns of wire should I use for primary and secondary windings ?

I don't know the impendance of the antenna connection of my radios (ATS 909 +
ICF SW100), so I intend to give a try with the coax I have in hand.

If it's a coax-type connector, the input should be about 50 ohms. If
it's screw terminals or a plug-in terminal, I'm guessing it's for
higher-impedance antennas like a random end-fed wire.

bob
k5qwg



Thanks in advance for your help,

Charly

balun spec depending on coax impedance
 

Bob Miller wrote:

On Wed, 01 Mar 2006 18:20:29 +0100, Charly wrote:


Dear all,

Usualy, people use 9:1 balun to connect a wire or dipole antenna to a 50 ohm coax.

A resonant dipole, I believe, is about 72 ohms. Connecting it through
75 ohm TV coax to a 50 ohm receiver input should be a near ideal
match.

On non-resonant frequencies, the dipole will present different
matches. That shouldn't be a problem, though, just for listening on a
sensitive receiver.

A balun won't give you a decent match except on the single frequency
it is designed for. That's one problem you run into, putting a balun
on a multi-band or multi-frequency antenna.

Single frequency?

dxAce
Michigan
USA

balun spec depending on coax impedance
 

On Wed, 01 Mar 2006 15:09:12 -0500, dxAce
wrote:



Bob Miller wrote:

A balun won't give you a decent match except on the single frequency
it is designed for. That's one problem you run into, putting a balun
on a multi-band or multi-frequency antenna.

Single frequency?

dxAce
Michigan
USA


At different frequencies the antenna will have different impedances
and the balun may or may not match.

bob
k5qwg

balun spec depending on coax impedance
 

On Wed, 01 Mar 2006 20:00:22 GMT, Bob Miller
wrote:

On Wed, 01 Mar 2006 18:20:29 +0100, Charly wrote:


Dear all,

Usualy, people use 9:1 balun to connect a wire or dipole antenna to a 50 ohm coax.

A resonant dipole, I believe, is about 72 ohms. Connecting it through
75 ohm TV coax to a 50 ohm receiver input should be a near ideal
match.

On non-resonant frequencies, the dipole will present different
matches. That shouldn't be a problem, though, just for listening on a
sensitive receiver.

A balun won't give you a decent match except on the single frequency
it is designed for. That's one problem you run into, putting a balun
on a multi-band or multi-frequency antenna.

That's not the point.

One of the big rules in impedance matching is that the load (gozinta)
have equal or higher impedance than the source (gozowta). You never
go from a HiZ generator into a LoZ cable. Major faux pas.

If the antenna's highest impedance is 450 Ohms, and it's going through
a 9:1 matcher it will never be choked by a 50 (or 75) Ohm cable.

Think of impedance as hose diameter and the signal as a solid stream
of water.