9:1 Balun

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Re: 9:1 Balun

Don Wilhelm
While it is "satisfying" to think of the ATU matching capability in
terms of SWR, that is not entirely valid.

A lot depends on frequency - at higher frequencies the "SWR matching
range" will be greater than on lower frequencies.

The only valid spec for the matching range is the available inductance
and capacitance in the ATu, as well as the step size.  The Elecraft
tuners do state that in their specifications.

The range for the Elecraft tuners is often quoted as a 10:1 SWR, but
that depends on a lot of factors, such as the frequency and the exact
impedance to be matched.

You may take the inductance/capacitance values in the Elecraft tuner
specs as well as the step size and run that data through an application
like TLA for windows (On the ARRL Antenna book CD or download from the
ARRL website) to find the actual SWR range that can be matched on any
tuner.  The resulting data is more informative than simply stating that
the ATU can match any particular SWR,

73,
Don W3FPR

On 1/31/2017 8:17 PM, K9MA wrote:
>  That's why ATU specs call out the
> SWR range.
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Re: 9:1 Balun

Don Wilhelm
In reply to this post by Kevin - K4VD
Kev and all,

A voltage "balun" can be tapped to produce a wide range of impedance
transformation possibilities, but the voltage balun will have no effect
on the problem of RF on the outside of the coax shield.
The modern consensus is that only common mode chokes should be used on
the feedline.  They should have enough inductance at the frequency of
interest to keep the RF off the outside of the coax.

See the works published by Jim Brown K9YC for a thorough discussion of
RFI and "baluns" (common mode RF Chokes) for use in the amateur
community - http://audiosystemsgroup.com/RFI-Ham.pdf.

73,
Don W3FPR



On 1/31/2017 8:35 PM, Kevin - K4VD wrote:
Can a BALUN be tapped maybe? It seems it would extend the range of
> internally antenna tuners also. I should know this stuff. But I don't.
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Re: 9:1 Balun

Kevin - K4VD
In reply to this post by Thomas Horsten
On Tue, Jan 31, 2017 at 8:53 PM, Thomas Horsten <[hidden email]> wrote:

> The ATU typically sits at the rig end where a balun sits at the antenna
> feedpoint


​There's the difference. I'm feeding my dipole with 600 ohm ladder line so
my 4:1 BALUN is right outside my window. The coax (heavily beaded) is only
about 3 feet long.​ I need to get the analyzer on it but I'm having
difficulty tuning up on 75 meters. Pretty much everything else tunes fine.

Kev K4VD
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Re: 9:1 Balun

Lynn W. Taylor, WB6UUT
In reply to this post by Kevin - K4VD
Oh, whatever power is generated by the transmitter is going to radiate.  
The classic example of "radiating power" that is completely and totally
uninteresting is when you dump the power into a resistor (a dummy load)
and the power is radiated as heat.

There is a contest where the participants take whatever metal stuff they
find lying around, load it up and operate.  It's proof that lots of
things can work, more or less.  The light-bulb example is another one.

I know that a 50 ohm source, going through a 50 ohm feedline into a 50
ohm load means minimal loss in the feedline.  If you have 1/4 wave of
coax with 100 ohm load the feedline will act as a transformer and you'll
have 25 ohms at the transmitter -- and that means power lost as heat.

It also means the length of the feedline, in wavelengths (and therefore
frequency) matters in the overall antenna system design.

That's why the balun should not be at the radio end, it should be near
the antenna.  If it's a permanent installation, taking the time to
figure it out and get everything matched up is a good thing.

Ladder line is well loved because it isn't as lossy as coax when things
aren't matched.

Tossing the radio (gently!) onto a picnic table at a park and throwing a
wire into the air is different.  Maybe it works, maybe it doesn't, but
you don't have a lot invested in the antenna system, and you can pick
wire lengths that'll be "good enough" -- and "good enough" often is good
enough.

This discussion started with what were good and bad lengths for an
ad-hoc, non-resonant wire.  Having some sort of 4:1, 9:1 or 16:1 balun
(or un-un) gets important if your wire happens to be near resonance.

73 -- Lynn

On 1/31/2017 5:35 PM, Kevin - K4VD wrote:

>
> On Tue, Jan 31, 2017 at 8:03 PM, Lynn W. Taylor, WB6UUT
> <[hidden email] <mailto:[hidden email]>> wrote:
>
>
>     That doesn't say the antenna would radiate it, but the transmitter
>     could make power and the tuner/transmission line would deliver it
>     to the radiat
>
>
> ​Why wouldn't the antenna radiate it? Seems to me if you can deliver
> power then what's not being radiated as heat would be radiated as RF.
> I have weird ideas about how all this works.
>
> One thing I think would be great to have, especially built in as part
> of an antenna tuner, is a switchable BALUN. When someone needs to
> throw up random antennas it would be handy to be able to just switch
> in the appropriate ratio. Can a BALUN be tapped maybe? It seems it
> would extend the range of internally antenna tuners also. I should
> know this stuff. But I don't.
>
> 73,
> Kev K4VD
>

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Re: 9:1 Balun AND "random antennas"

Richard Fjeld-2
In reply to this post by Jim Brown-10
Jim,

If you don't object, I'd like to save this and forward to people as
arguments develop on these subjects.

  I wish you had touched on '4:1 baluns'.  Except for this group, so
many people I talk to think a balun should be 4:1, even in their
tuners.  I think it is DX Engineering that addresses this well.

Dick, n0ce


On 1/31/2017 12:50 PM, Jim Brown wrote:

> All of this discussion becomes badly confusing by failing to describe
> these circuit elements by their real name. The word "balun" is a
> bastard -- it is widely used to describe nearly a dozen things that
> are VERY different from each other.
>
> W4TV got it right by adding the correct description, and this post
> starts to get at it, but adds another bastard word, unun.
>
> Two-windings that are coupled by a magnetic field are a TRANSFORMER.  
> If the two windings have a terminal in common, they are an
> AUTO-TRANSFORMER. A coil of coax is a common mode choke (and not a
> good one). A section of transmission line wound around a ferrite core
> is a COMMON MODE CHOKE, and if well designed (choice of ferrite
> material, number of turns) can be a very good one.
>
> Transformers and auto-transformers transform impedance by virtue of
> their turns ratio. Arrays of common mode chokes can also be used to
> match circuits of different impedances.
>
> Last I looked, there was no description of the Elecraft "balun"
> telling us what it is. Perhaps Eric or Wayne could add that to the
> catalog listing for it.
>
> Another point. SWR is NOT an indicator of how well an antenna works.
> High SWR DOES increase loss in a feedline, but that matters only with
> long feedlines and small diameter coax. That does NOT matter for
> typical portable (or even mobile) operation, where feedlines are much
> too short for loss to matter.
>
> A high value of SWR as seen by a transmitter DOES limit that power
> that the transmitter can put into the antenna. That's where the
> antenna tuner comes in -- it transforms the impedance at the
> transmitter end of the feedline (or the end of a wire plugged into the
> coax connector combined with the counterpoise connected to the
> chassis) to the 50 ohm resistive impedance that the transmitter wants
> to drive.
>
> If we make RF current flow in a wire, it will radiate. How well it
> radiates depends, of course, on its orientation. A wire laying on the
> ground doesn't radiate very well. :)  A wire without a counterpoise
> will use whatever it sees as a signal return. If that return happens
> to be the earth, the earth, which is essentially a big resistor, will
> burn much of the transmitter power. The "good" lengths of wire Wayne
> and those spreadsheets list are simply lengths that are likely to
> present an impedance within range of most antenna tuners for the bands
> that the operator is likely to use.
>
> 73, Jim K9YC
>
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Re: 9:1 Balun

Ignacy
In reply to this post by Thomas Horsten
Practical side only.

Assume you use a random wire antenna. AT in K2 or KX3 will not match all bands directly. It will match with BL1 or BL2 in 4:1 mode. This is because:
1. After transformation, the impedance is more manageable to KAT2 or KXAT3.
2. Loss in balun. Mainly on lower bands with short antennas.

Whenever I have space for BL1, I use it. It is no brainer as I prefer the match than no match and balun overheat than AT overheat. Heating occurs mainly at bands were the wire is too short.  

New transformers can have extremely low loss. A 64:1 transformer used for 40-10 or 80-10 endfeds at myantennas.com is just warm at a KW level.

Ignacy, NO9E

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Re: 9:1 Balun AND "random antennas"

Jim Brown-10
In reply to this post by Richard Fjeld-2
Hi Dick,

Sure, you're welcome to forward stuff like this.

As to stuff on my website -- I do NOT permit it to be copied to other
websites, but I DO encourage links to it.

73, Jim K9YC

On Wed,2/1/2017 8:16 AM, Richard Fjeld wrote:

> Jim,
>
> If you don't object, I'd like to save this and forward to people as
> arguments develop on these subjects.
>
>    I wish you had touched on '4:1 baluns'.  Except for this group, so
> many people I talk to think a balun should be 4:1, even in their
> tuners.  I think it is DX Engineering that addresses this well.
>
> Dick, n0ce
>
>
> On 1/31/2017 12:50 PM, Jim Brown wrote:
>> All of this discussion becomes badly confusing by failing to describe
>> these circuit elements by their real name. The word "balun" is a
>> bastard -- it is widely used to describe nearly a dozen things that
>> are VERY different from each other.
>>
>> W4TV got it right by adding the correct description, and this post
>> starts to get at it, but adds another bastard word, unun.
>>
>> Two-windings that are coupled by a magnetic field are a TRANSFORMER.
>> If the two windings have a terminal in common, they are an
>> AUTO-TRANSFORMER. A coil of coax is a common mode choke (and not a
>> good one). A section of transmission line wound around a ferrite core
>> is a COMMON MODE CHOKE, and if well designed (choice of ferrite
>> material, number of turns) can be a very good one.
>>
>> Transformers and auto-transformers transform impedance by virtue of
>> their turns ratio. Arrays of common mode chokes can also be used to
>> match circuits of different impedances.
>>
>> Last I looked, there was no description of the Elecraft "balun"
>> telling us what it is. Perhaps Eric or Wayne could add that to the
>> catalog listing for it.
>>
>> Another point. SWR is NOT an indicator of how well an antenna works.
>> High SWR DOES increase loss in a feedline, but that matters only with
>> long feedlines and small diameter coax. That does NOT matter for
>> typical portable (or even mobile) operation, where feedlines are much
>> too short for loss to matter.
>>
>> A high value of SWR as seen by a transmitter DOES limit that power
>> that the transmitter can put into the antenna. That's where the
>> antenna tuner comes in -- it transforms the impedance at the
>> transmitter end of the feedline (or the end of a wire plugged into the
>> coax connector combined with the counterpoise connected to the
>> chassis) to the 50 ohm resistive impedance that the transmitter wants
>> to drive.
>>
>> If we make RF current flow in a wire, it will radiate. How well it
>> radiates depends, of course, on its orientation. A wire laying on the
>> ground doesn't radiate very well. :)  A wire without a counterpoise
>> will use whatever it sees as a signal return. If that return happens
>> to be the earth, the earth, which is essentially a big resistor, will
>> burn much of the transmitter power. The "good" lengths of wire Wayne
>> and those spreadsheets list are simply lengths that are likely to
>> present an impedance within range of most antenna tuners for the bands
>> that the operator is likely to use.
>>
>> 73, Jim K9YC
>>
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>

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