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

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

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

In article ,
Bob Miller wrote:

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.

Antenna reactance and impedance are two different things. The antenna
impedance in this case is a characteristic of the single wire or a
dipole. The first case is hundreds of ohms and the second about 72
ohms. And like you stated in another post in the thread he does not
need a BALUN for the dipole.

The purpose of a BALUN, UNUN or other types of impedance matching
device is to match the characteristic impedance of the antenna to the
transmission line, which in this case is the coax.

The impedance transformers do not tune the antenna and don't deal with
antenna reactance to a certain frequency.

It seems people make this mistake all the time.

--
Telamon
Ventura, California

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.

On Wed, 01 Mar 2006 20:37:16 GMT, David wrote:

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.

Why do you think an antenna for multi-frequency use has an impedance
no higher than 450 ohms? As an example, check the impedances of the
all band doublet at http://www.cebik.com/wire/abd.html

bob
k5qwg



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

On Wed, 01 Mar 2006 22:48:03 GMT, Bob Miller
wrote:


Why do you think an antenna for multi-frequency use has an impedance
no higher than 450 ohms? As an example, check the impedances of the
all band doublet at http://www.cebik.com/wire/abd.html

'cause Steve is my lord and saviour.

http://www.hard-core-dx.com/nordicdx.../magbalun.html

David wrote:

On Wed, 01 Mar 2006 22:48:03 GMT, Bob Miller
wrote:

Why do you think an antenna for multi-frequency use has an impedance
no higher than 450 ohms? As an example, check the impedances of the
all band doublet at http://www.cebik.com/wire/abd.html

'cause Steve is my lord and saviour.

http://www.hard-core-dx.com/nordicdx.../magbalun.html

Please note that I no longer offer the matching transformers for sale.

Why?, one might ask. Well, I sold between 400 and 500 of them and quite frankly
I got tired of winding the darn things up.

I still get the occasional inquiry.

dxAce
Michigan
USA

On Wed, 01 Mar 2006 18:15:07 -0500, dxAce
wrote:



David wrote:

On Wed, 01 Mar 2006 22:48:03 GMT, Bob Miller
wrote:

Why do you think an antenna for multi-frequency use has an impedance
no higher than 450 ohms? As an example, check the impedances of the
all band doublet at http://www.cebik.com/wire/abd.html

'cause Steve is my lord and saviour.

http://www.hard-core-dx.com/nordicdx.../magbalun.html

Please note that I no longer offer the matching transformers for sale.

Why?, one might ask. Well, I sold between 400 and 500 of them and quite frankly
I got tired of winding the darn things up.

I still get the occasional inquiry.

dxAce
Michigan
USA

I wish these were around back in '97 when I drove to Escondildo to get
a Palomar MLB for $40 for my 120' all steel random wi

http://www.geocities.com/qrp_baluns/E-LMZ-50-640.gif

In article ,
Bob Miller wrote:
Why do you think an antenna for multi-frequency use has an impedance
no higher than 450 ohms? As an example, check the impedances of the
all band doublet at http://www.cebik.com/wire/abd.html

You don't understand. We're not transmitting.

The goal in not some absolute effiency for raditating RF energy or babying
the RF final amplifier, but maximising the signal to noise ratio of the
signal fed into the receiver.

At low cost.

There's great improvment with these transformers because you can
stick some random hunk of hookup wire out in weeds, far enough away
from the computers, light dimmers and other modern electronic crap.

And if your receiver doesn't have high impedance input, you'll get
even more signal off a random wire, with either the transformer remotely
located or at the receiver.

With receivers, it's all relative.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)