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Author Topic: Will a Balun work "backwards?"  (Read 6839 times)
K5JCJ
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« Reply #15 on: July 01, 2010, 11:02:38 PM »

If you want some good honest work on baluns, and balun types, you have a couple of choices.

Certainly, Tom's, W8JI, (http://www.w8ji.com) has some of the best on the net, as does Owen, ZK1OD (http://www.vk1od.net).

I think the original poster was asking about a tapped UNUN which is a type of transmission line transformer. He also referenced a Hamstick antenna, and wanting better performance. Adding a UNUN or balun isn't going to do anything for the Q of the coil, where it's the biggest loss in a Hamstick. Adding insult, is the low mounting which causes a goodly portion of the return current to flow through the lossy surface under the vehicle, rather than through the vehicle's superstructure. Both of these factors make the input impedance very close to 50 ohms, so better matching isn't a way of increasing performance in this case.

The poster mentioned he was using LM400, when LM200 would have been just as good. The smaller coax would also allow the use of a multi-turn common mode choke, which would probably do as well for performance (less ingressed common mode noise).



I appreciate you taking the time to respond to my original inquiry, I didn't expect my thread to get hijacked into a general discussion about baluns. The balun I was using was an W2AU 1:1 Balun, mainly because I just had it laying around, and same deal for the LMR400. But it looks like I am going back to the drawing board with this setup and may re-mount the antenna and switch to an 102 inch whip instead. I park at work in a garage every day so a hamstick, bumper mounted with really trimmed whip, was the best option for me because anything else higher would get destroyed after a few days.

But thanks for the input, it was helpful!

73,
John K5JCJ
New Orleans
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KM3K
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« Reply #16 on: July 02, 2010, 10:27:56 AM »

Yes

Wow, not very much negotiating room there.
Almost makes me ask myself what part of yes don't I understand. Wink

Just a note to the cautious reader about using a balun backwards...

Dr. Sevick W2FMI (SK) has categorically written about the 1:4 Ruthroff-balun (voltage-balun):
"The Ruthroff balun only works in one direction. The high-impedance side is always the balanced side. The Guanella balun, on the other hand, is bilateral. It can work as well in either direction, depending on which terminal is grounded. Therefore, a Guanella balun can easily be designed to match a 50-ohm coaxial cable to a 12.5-ohm balanced load."

With that in mind, I still wonder though what feature of a 1:4 Ruthroff-balun (voltage-balun) suffers when using it "backwards".
Someday, I'll try to answer my question.
73 Jerry KM3K



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K6LHA
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« Reply #17 on: July 05, 2010, 12:18:32 PM »

A balun or unbal or unun or balbal or whatever funny name one can think up all have one fundamental property:  THEY ARE ALL PASSIVE, WIDEBAND TRANSFORMERS.

As such, they have no magical properties of by themselves propagating RF energy in only one direction.  Neither is there any sepearate "voltage" or "current" balun.  Voltage and current always go together to propagate RF energy...whether held "captive" in a transmission line or "converted" to an EM envirnonment.

A toroidal form with a powdered-iron or ferrite core of a WIDEBAND RF TRANSFORMER is used to keep the magnetic field close to the form and limit the electric field.  The main purpose of that, besides increasing the efficiency of power transform (i.e., reduce insertion loss and wasted heat) is also to limit any coupling from stray reactances to a conductive container or to other conductive things close to that WIDEBAND RF TRANSFORMER.  To a lesser degree, non-conductive thingies close to that transformer may also add (unseen, probably un-noticed) reactances just from the change in dielectric constant close to the form.

A basic check on a WIDEBAND RF TRANSFORMER is to use balanced windings.  How to hook it up to existing test equipment (if any available at all) is up to the testing person.  Hint: Do not use coaxial connectors, even if in a plastic box; that should be evident without saying so...it would make it unbalanced on one side compared to the other and the "balbal" is somewhere between an "unun" and a "balbal."

If an balanced-to-balanced WIDEBAND RF TRANSFROMER checks out and gives some reasonable measured data, then try unbalanced-to-unblanaced connections.  Roughly, the only difference would be slight with the normal losses showing up as roughly the same insertion loss comparing all-balanced and all-unbalanced.  A common mistake is to use a plastic box without any common, big (very low impedance) conductive connection between unbalanced coaxial outer conductor connections for an "unun".  It is surprising to me how many have done that without thinking.

Okay, now that a WIDEBAND RF TRANSFORMER is checked out, hooking it up with another one or some RF load or whatever now becomes more complicated to figure out.  That's why some network theory is introduced in books or classes.  It is a common failing in such books or classes that the presentation isn't that good, a fault of the instructor or writer, not the subject.

Hooking up WIDEBAND RF TRANSFORMERS can be done to make a very good one-way path for RF energy down a transmission line (those have been made for half a century in the microwave RF industry as "directional couplers") or have bilateral, independent paths with separate amplifiers in each one-way path (unsed for longer than a half century in long-distance wired telephone lines).  They can be used in bridges for measurement.  They can be used for just about any application at RF one wants to think about.  However, the only way to really know for sure is to get on the bench and do some measurements with as much thinking as necessary while doing so.

The alternative is being seduced by advertising phrases while NOT caring to do anything more than "empirical data derivation" (just connecting it and see what happens without any sort of measurements).  Once one knows the "ad-speak" then one can go around expounding with that and sound the "expert" without breaking a sweat on any mental synapses.

All of the analytical models seen in texts assume the reader understands how to hook them up in the practical case.  Offhand, I'd say that few actually do that.  They don't think of lead length or inductance contributed by a hook-up wire, the capacitance to ground from supposedly-floating connections, or a thousand and one other things possible.

One can mess up an unbalanced winding by using too long a conductive path on an unbalanced winding "ground" end.  One can mess up a balanced winding by having too much capacitance to (even a good ground plane) on one end versus the other end.  It is even possible to upset a center-tap of a balanced winding in a few odd ways; the balanced winding is no longer truly balanced above ground.

Motorola once published some excellent AppNotes on wideband RF transformers for semiconductor power amplifiers from HF on up into VHF, nealy all by the late Helge Granberg.  Detailed construction notes and pictorials.  Mostly balanced to unbalanced WIDEBAND RF TRANSFORMER structures using wire and cores and some odd PCB pieces.  They got that way through some plain old skull sweat and applying basics, rules, known laws of physics, without using any magic words or special jargon just for amateurs.  If one paid attention, they WORKED well.  All without using a single "pi-network" limited to lower frequencies.

MILLIONS of plain old telephone deskset "hybrid" transformers were built worldwide in the last 3/4-century for audio frequencies.  They had separate send and receive paths for AF plus a path for 20 Hz ringer signals and an added sidetone so that users wouldn't think their mouthpiece had gone dead.  Sure, it is only for audio and uses iron-core transformers but the principles apply regardless of frequency.

Tens of thousands of "hi-fidelity" amplifiers have been made with AF response going from 20 Hz to 30,000 Hz into speakers through transformers.  Sure, still audio, but then the lowest ITU-R frequency allocation is 9 KHz for EM propagation.

Millions of old analog TV receivers have been built in the last half-century with one tiny UNBAL built into them...for the sole purpose of changing 75 Ohm unbalanced coaxial input to 300 Ohm balanced input (or vice-versa) over multiple octaves of RF frequency range.  Those can be sluffed-off as denigratory "low power" but the power difference is just a matter of size, cost, and application.  The principle is still the same.

73, Len K6LHA
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KM3K
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« Reply #18 on: July 05, 2010, 08:39:53 PM »

A balun or unbal or unun or balbal or whatever funny name one can think up all have one fundamental property:  THEY ARE ALL PASSIVE, WIDEBAND TRANSFORMERS.
As such, they have no magical properties of by themselves propagating RF energy in only one direction.  Neither is there any sepearate "voltage" or "current" balun.  Voltage and current always go together to propagate RF energy...whether held "captive" in a transmission line or "converted" to an EM envirnonment.

To Len K6LHA,

Hey, hey, hey, where to start in reply  ....

Man, IMHO, most definitely spring some cash for both of Dr. Sevick's books about baluns/ununs to do some serious studying on 'Transmission-Line-Transformers' (TLT) and then retract some statements made in your posting.

Comments:

1. "Wideband conventional Transformer" action is undesired in a TLT but is tolerated at the low-frequency end.

2. Sevick has a graph showing how vastly inferior a "wideband conventional transformer" is relative to a TLT.

3.The labelling of 'current-balun' and 'voltage-balun' in the context used relative to baluns is valid.

4. It is very important to understand that theoretically, in a TLT, there is no flux in the core.
Now, in actuality, there will be a minor anmount due to:
a) we can not make a perfect transmission-line.
b) for several other reasons, we might expect a very small unbalanced current.

73 Jerry  KM3K
 

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K6LHA
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Posts: 349




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« Reply #19 on: July 06, 2010, 11:41:46 AM »

Man, IMHO, most definitely spring some cash for both of Dr. Sevick's books about baluns/ununs to do some serious studying on 'Transmission-Line-Transformers' (TLT) and then retract some statements made in your posting.

Thank you but I decline.  Unless there is some definite technical reason other than some terminology, then I would not need basic principles and AppNotes (as they applied) for at least the last four decades of my work making successful RF hardware...i.e., working hardware, satifying specifications.
 
Quote
1. "Wideband conventional Transformer" action is undesired in a TLT but is tolerated at the low-frequency end.

"Tolerated?!?"   Grin

Quote
2. Sevick has a graph showing how vastly inferior a "wideband conventional transformer" is relative to a TLT.

I've seen thousands, used hundreds of graphs, and all have some information that can be useful.  The only ones which I would dub "vastly inferior" are those with bad reproduction so as to make observation difficult.

Quote
3.The labelling of 'current-balun' and 'voltage-balun' in the context used relative to baluns is valid.

Then please explain what those two terms are.  Any transformation of RF energy in a passive device involves both current and voltage.  For decades I've done transformations, either through what many think of as a "transformer" or through other devices (particularly in distributed-constant form).  For decades my lab cowarkers, people with letters behind their names, have thought of impedance changing as in characteristic impedance changing of ports.  There is no "voltage" transformation alone or "current" transformation alone.  If it were so, then an active device would be in there supplying RF energy.

Quote
4. It is very important to understand that theoretically, in a TLT, there is no flux in the core.
Now, in actuality, there will be a minor anmount due to:
a) we can not make a perfect transmission-line.
b) for several other reasons, we might expect a very small unbalanced current.

This is the first time I recall encountering the term "TLT."  I'm beginning to suspect my leg is trying to be pulled here.  [like you forgot the letter I in that supposed acronym]       Grin

Sorry, but there is no such thing (so far known, that is) where a transformer "has no (magnetic) flux" in it.  There ALWAYS IS magnetic lines of force there.  What is desired is to CONTAIN those lines of force and toroidal forms do that very nicely without a lot of fuss and bother.  ["pot cores" do it better at HF and lower than a torus form but those cores are expensive, hard to get now]

In terminology, the word "wideband" isn't always explained.  Usually (most every place exept in ham radio venues) that word means a useful frequency span of an octave to a decade, perhaps more.  "Bandwidth" (more properly band-span symantically) depends a lot on core material characteristics.  It is hard for any human to "see" iron-powder or ferrite material and know immediately what it is.  For that we have to do frequency versus RF energy transfer plots to gauge roughly at its characteristics.  It can't be done at very low frequencies either using silicon-alloy laminations for a core (such as 60 Hz) without some fancy instrumentation.

Show me any transformer that is nearly "flux free" and I'll show you someone who spent a lot of time with alcohol or other solvents to make its interior very clean...

73, Len K6LHA

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KM3K
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« Reply #20 on: July 06, 2010, 03:50:13 PM »

To Len K6LHA,
Please give me about a couple days or so to do a real job in replying to your earlier posting today.
I have drafted a broad outline on TLT operation and it now needs to be embellished.
Besides, it was my practice, as a design-engineer (most of my adult life), to never sign-off a drawing until I looked it over again the next day; amazing how different a work looks after 24 hours have gone by.
73 Jerry KM3K
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KM3K
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« Reply #21 on: July 09, 2010, 01:21:59 AM »

This is the first time I recall encountering the term "TLT."  I'm beginning to suspect my leg is trying to be pulled here.
73, Len K6LHA

Hi Len K6LHA…….

In the spirit of the hobby, I pass along what I have learned and don’t profess to know all the answers.
I’ve had to stop work on this, so WYSIWYG; I feel it needs editing to remove some repetition near the end but it is what it is.

1. The primary reason for this work is to explain how a particular Transmission-Line-Transformer (TLT) known as a 1:1 Guanella-balun operates.
Three other commonly used names to describe this balun are: “current-balun”, “isolation-balun”, and “choke-balun”; I’d suggest committing all four names to memory.
The 1:1 Guanella-balun is the basic building block for other types of types of Guanella-baluns or ununs (a Guanella-unun is just a Guanella-balun with the grounds in different places; a similar statement for Ruthroff-ununs cannot be made).
Also, I’ve included ‘back-ground’ info, which I thought may help in understanding.

2. About the word “balun”….
It means “balanced-to-unbalanced”; Guanella (a Swiss engineer in 1944) needed to match a balanced (push-pull) amplifier to an unbalanced load; hence the name.
However, these days we generally are going unbalanced-amplifier to balanced-antenna load.
So, “unbal” would be a more appropriate term but we are stuck with balun.

3. It is most important, for the time being, to absolutely and completely put out of mind the concept of the conventional transformer and its flux-linkages.

4a. This section explains the very first 1:1 Guanella-balun.
As part of his development work in 1944, Guanella coiled a transmission-line.
The historical record, that I’ve accessed, is meager on the details of the transmission-line that he used but it is reasonable to presume he used coax (Heaviside had patented coax in 1880 & Bell Labs began making coax in 1929).
In coiling the line, Guanella intentionally formed a choke, whose conductor was the exterior surface of the coax’s shield. Recall that skin-effect is operative on a coax-shield at radio-frequencies, so the transmission-line current is on the shield’s inside surface and the harmful “common-mode currents” and so-called “antenna-current” is on the shield’s outside surface.
It is the choke that limits these harmful currents; these currents do cause flux in the core.
As Guanella showed on his schematic, this choke is in parallel with the transmission-line.
This choke serves to isolate the input from the output and so suppresses any conventional transformer current and allows transmission-line current to flow.
So that’s it; we have a 1:1 balun made with an air-core and, in that core, there are no flux-lines from the transmission-line currents.

4b. The seminal work by Joe Reisert W1JR in 1978 enhanced the 1:1 balun idea further by winding that coil of coaxial transmission-line on a toroid-core. Here also, by virtue of the coax’s inherent shielding feature, we certainly can see there are no flux-lines introduced into the toroid-core when just balanced transmission-line currents are flowing.
W1JR also invented a unique way to wind the coil and here is a link to a site showing that winding-technique:   http://www.balundesigns.com/servlet/the-63/balun-designs-1-cln-1-Isolation/Detail
Notice the plastic jacket has been taken off the coax leaving the shield exposed; easier to wind and can put on more turns.

4c. Without giving up much in performance, one can modify W1JR’s coax design to use a two-wire transmission-line where the two-wires are held together to maintain a desired characteristic impedance.
The site called up by this link shows an example:
    http://www.balundesigns.com/servlet/the-98/isolation-choke-balun-common/Detail
A paragraph later in this work has some verbiage about the characteristics of two-wire lines.

4d. Another ingenious style “current-balun” is W2DU’s beaded-balun, where coax-cable is passed through ferrite-beads to form chokes ; although simple in concept, proper core permeability choice is needed to prevent cores from breaking due to excess heating of the cores.

5. A different 1:1 balun is a “Ruthroff-balun”; named after its Bell-Labs inventor in 1959.
Another name for the “Ruthroff-balun” is “voltage-balun”.
As I see it, the voltage-balun generally is inferior to the Guanella-balun.

6. We can make a 1:4 Guanella-balun by connecting two 1:1 Guanella baluns such that the inputs are in parallel and the outputs are series connected per either the ARRL’s 2007 Handbook or Antenna-book; a comment that neither book has any text on the importance of the transmission-line’s characteristic-impedance. In an earlier posting, I provided the rules for that significant item.

7a. Overall, the 1:1 balun is the most frequently used balun.
7b. Second place in usage is the previously mentioned 1:4 balun (for example, 50-ohm-to-200-ohm), which can be a Guanella or Ruthroff design; strong arguments can be made for each design approach.
7c. The reader should be aware there is a myriad of other impedance-ratio possibilities made up from combinations of current-balun and/or voltage-baluns; one use is to match vertical-antennas.

8a. In a TLT, energy is transferred from input to output by means of a transmission-line
Although hams are very adept in using transmission-lines like coaxial-cable or two-wire ladder-line to move the transmitter’s output to an antenna, it is a difficult to think of the conductors  as transmission-lines in the balun. One tends to think they are just two wires wound around a core.
8b. Concerning a transmission-line, the US-Army manual TM11-675 (Aug 1951) has that “…the greater portion (about 90%) of the transmitted energy is in the electromagnetic waves that the line conductors guide through the space between them. In general, less than 10% of the transmitted energy is actually in the conductors of which a well-designed line is comprised.”
  (Comment by KM3K: I have not seen these statements anywhere else.)
8c. In a transmission-line, there are two conductors (spaced as in two-wire-line or as in coax).
There is an electric-field between the two wires.
Each wire has its own magnetic-field.
These fields are related in a way that only the Divine Creator fully understands but Heaviside, drawing on Maxwell’s work, was able to express mathematically and we are not going there at all.
For two-wire-line, the energy is confined to the immediate region around those wires.
For coax, the energy is confined between the center-wire and the shield (assuming a good shield).
The electromagnetic signals we will be using will be Transverse-ElectroMagnetic (TEM) waves; that is, the standard HF and VHF ham-band stuff.

9. The TLT can be made in several different ways:
  a) coiling loops of coax (which means we have an air-core),
  b) winding either coax or two-wire on a toroid-core or ferrite-rod.
To quote Dr. Sevick W2FMI (SK) about the TLT, “….it is both a choke (a lumped element) and a transmission-line (a distributed element).”
The toroid-core has enhanced performance over the other methods, although the other methods have appealing attributes like simplicity of winding and cost.

10. In his seminal ARRL 1985 article, Roy Lewallen W7EL introduced the terms of “current-balun” and “voltage-balun”.
Here is a link; it is a good read…. http://www.eznec.com/Amateur/Articles/Baluns.pdf
Both baluns work by the transmission-line mode.
The current-balun (Guanella) puts equal current into/out-of its output terminals; highly desired feature.
The voltage-balun (Ruthroff) puts equal magnitude voltages at its output terminals.

11. It is important to comment on the impressive frequency range of a well-designed current-balun.
Earlier in this reply, I provided a link to a toroid wound with coax; that commercially produced 1:1 current-balun at 50-ohms, wound on a toroid-core with coax, has a passband from 1 to 54 MHz with very, very low insertion-loss and very high choking-impedance.

12. Moving energy in a balun from input to output by the transmission-line mode on a toroid-core means that theoretically there is no flux in the toroid-core.
Now, in actuality, because we cannot make a perfect transmission-line, we can expect there will be some accidental flux but nowhere near the magnitude from a conventional transformer.
It is easy to understand why there is no flux for well made coaxial-cable.
But it may not be so clear for two-wire transmission-line.
So here is why there is no flux in the toroid-core for a theoretical two-wire transmission-line:
  a) the current in each wire is equal but going in opposite directions; should be 180 deg out-of-phase.
  b) this means the magnetic-fields caused by those currents are also opposite and cancel each other out everywhere except in the very immediate region between the two wires.
  c) because the magnetic-fields largely cancel everywhere, there is no net flux in the core, which in turn means no concerns about core saturation and all the problems that can bring.

13a. If the balun-designer is not careful, it is possible for the balun to conduct conventional transformer currents rather than the desired transmission-line currents.
Winding the transmission-line on the toroid-core makes a choke; hence the name “choke-balun”.
The choke has a reactance and it serves to isolate the input from the output and works to prevent conventional transformer currents; we want that reactance to be at least 5 times (some authors say 10x) the load resistance.
Although more turns makes more reactance, it adds parasitic capacitance between the windings and that harms the high frequency responses.

13b. In a voltage-balun, in spite of good design efforts, invariably at the lower frequencies there will be conventional transformer currents and attendant flux-linkages in the core; this causes the low frequency range to suffer performance (typically higher insertion-loss).
Low frequency models for 1:4 voltage-baluns look like a conventional transformers.

14. If the 1:1 current-balun is used in a 50-ohm system, then the transmission-line’s characteristic-impedance used in the balun is 50-ohm.
One factor in the high-frequency limit of the balun is determined by how close to 50-ohm is that transmission-line’s characteristic-impedance; parasitic generally are absorbed but can be another factor.

15. Key uses for the 1:1 current-balun:
a) is to marginalize the “inverted-L current” in the transmission-line feeding a dipole-antenna.
This will prevent a radiating Feedline and prevent distorting the antenna’s radiation pattern.
There will be some flux in the core but it’ll be minor due to the small current causing it.
This problem is covered at length in the 2007 ARRL Antenna-Book.
b) drive balanced antennas (e.g. dipole or yagi) with equal currents.

I hope this was of some interest and help to my fellow hams.

Len, I could email to you the plot, from Sevick’s book, which shows the superiority of the balun over a conventional transformer; your email-address is hidden; mine is there, so let me know by email if you’d like the plot.

73 Jerry KM3K
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K0BG
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« Reply #22 on: July 09, 2010, 06:16:33 AM »

Well done, Jerry.
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K6LHA
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« Reply #23 on: July 11, 2010, 01:51:41 PM »

In the spirit of the hobby, I pass along what I have learned and don’t profess to know all the answers.
Thank you for your effort.  As for clear, concise writing (plus illustrations), I would have thought that Roy Lewallen's good link from 1985 could have answered everything.
Quote
I’ve had to stop work on this, so WYSIWYG; I feel it needs editing to remove some repetition near the end but it is what it is.
There was never any hurry to get it out perfect.  As I found out on returning to the house, it was only re-posted as an Article on E-Ham.
Quote
1. The primary reason for this work is to explain how a particular Transmission-Line-Transformer (TLT) known as a 1:1 Guanella-balun operates.
Three other commonly used names to describe this balun are: “current-balun”, “isolation-balun”, and “choke-balun”; I’d suggest committing all four names to memory.
I'd suggest not suggesting so many things for others to "commit."  Cheesy

Quote
The 1:1 Guanella-balun is the basic building block for other types of types of Guanella-baluns or ununs (a Guanella-unun is just a Guanella-balun with the grounds in different places; a similar statement for Ruthroff-ununs cannot be made).
Since the "Guanella" balan was originated by Guarnella, then it couldn't be called a "Ruthroff" balun, could it?  Cheesy
Quote
Also, I’ve included ‘back-ground’ info, which I thought may help in understanding.
Actually, very little to be frank about it.  "Widebandedness" in electronics has been commonplace since the year dot...followed by components for RF, including balanced transmission line studies, something that Lee de Forest had been studying some time before he got into glass-enclosed vacuum things he called "Audions."

Low-frequency transformers had been around since before World War One but there was precious little in the way of test equipment to test their responses over frequency.  Bridges could measure things to a limited degree although they were capable of more precision...if they had a good frequency source and a good detector.

Two decades, the 1920s and 1930s, proved to be the first breakthrough for establishing standards and standardizations in electronics (which includes 'radio'), academically and industrially.  Industrially, wires shielded by an insulated braid had been made for a decade before 1929 but it took better academic smarts and equipment to categorize it as "coaxial cable" suitable for REALLY broadband RF use.

There isn't a lot of information available on coaxial cable in the press prior to 1940, nor of transformers wound on torus forms, nor of powdered-iron cores for inductors nor of ferrites for same or microwave applications.  Those were too new in the electronics world at the time.  [ferrites are heat-sintered iron alloy powders whereas slug-tuned-powdered-iron-alloy-molded-in-plastic inductors are usually misnamed as "ferrite core").

The world prior to 1940 was largely big and bulky and "transmission lines" were the balanced-wire types, most as "600-Ohm" spacings common to the huge telephone infrastructure.  That large spacing was good for HF transmitters up to 50 KW.  Such transmitters of 500 W or better used Link Coupling from (narrowband) resonant circuits to transform, say, 5000 Ohms down to 600 Ohms or less; just a "link" of a fractional-percentage of windings relative to the main resonant "tank."  To couple several wire antenna elements the techniques involved either a "black box" of L and C networks or varying characteristic-impedance balanced lines.  Antennas for HF were BIG.  Technology of RF Power Amplification was not yet advanced and stabilized on practices for broadcasting service.

Quote
2. About the word “balun”….
It means “balanced-to-unbalanced”; Guanella (a Swiss engineer in 1944) needed to match a balanced (push-pull) amplifier to an unbalanced load; hence the name.
Can't be it with that sentence.  The resonant impedance of push-pull vacuum tube amplifier plate circuits was still too high to do it with open-wire lines and WAY too high to do it with coaxial cable.  The "transistor" would not appear until 3 years after 1944 and then for another decade until some were big enough for power applications.

The word itself IS nice, compact, and easy to pronounce as a contraction of a longer hyphenate construct.

But, what the heck, the Phase-Locked Loop was patented in 1932 in France.  Took a bit longer to develop transistors into practical producible semiconductors, then to make them into integrated circuits to bring them into the first practical Frequency Synthesizers.  In that interim we did have "locked oscillators" and related tube circuits but those weren't widespread except in labs and in TV broadcasting.

Quote
However, these days we generally are going unbalanced-amplifier to balanced-antenna load.
So, “unbal” would be a more appropriate term but we are stuck with balun.
Well, I didn't know WE were ALWAYS doing that kind of transformation.  "Balanced loads" are things like dipoles (particularly wire kinds) while "unbalanced loads" are things like "monopoles" (half a dipole above an "infinite" ground plane).  <shrug>

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3. It is most important, for the time being, to absolutely and completely put out of mind the concept of the conventional transformer and its flux-linkages.

NO WAY!  BOTH, repeat BOTH Electrostatic AND Magnetic fields are THERE.  "TEM" is a description of a typical field combination in coaxial structures, Electrstatic and Electromagnetic (the "E" and "M" of "TEM" respectively).  In waveguide the there is more abbreviation wherein a field is described as "TE" or "TM" with a suffix of a double number to denote fields which are much better shown in illustrations than text.   Those fields were deliniated and described just before WWII started for the USA.  See the "Rad Lab" series of volumes available just after WWII.

Please try to NOT use "flux-linkages."  Just think of them as MAGNETIC FIELDS.  Way back in JCM's day there was no way to think about magnetism as any sort of human-sensed force so the best thing that came to mind then was an all-purpose word like "flux."  "Lines of (magnetic) force" is equally devoid of any human sense relationship but that is still used in iron-laminate power transformer design.  We humans can sense electrostatic shock as a secondary symptom but not much as a natural force.

The word "transformer" in electricity has become common but only in the sense that it TRANSFORMS AC voltage higher or lower but doesn't do too much about AC energy; as AC voltage is transformed, so is AC current transformed inversely to (generally) preserve the AC energy.

[this is Part 1 of a reply...Part 2 follows]
K6LHA


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K6LHA
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« Reply #24 on: July 11, 2010, 01:59:00 PM »

This is Part 2 of the same reply - LHA

4a. This section explains the very first 1:1 Guanella-balun.
As part of his development work in 1944, Guanella coiled a transmission-line.  The historical record, that I’ve accessed, is meager on the details of the transmission-line that he used but it is reasonable to presume he used coax (Heaviside had patented coax in 1880 & Bell Labs began making coax in 1929).
What is lacking here is the WHY of the APPLICATION of using any "balun" or whatever, ESPECIALLY if there was no impedance change required.  Of course, the "balanced" and "unbalanced" relative to the so-called "infinite ground" will be an alleged "reason" but, in 1944, how many 50 Ohm coaxial cables (or other impedances) needed to be transformed?  NETWORK Theory was good enough to design and predict all sorts of (relatively narrowband) RF networks as used in AM broadcasting...and many wideband applications such as in television broadcasting.  I'm omitting a LOT of work all over the EM spectrum on what was done from the 1930s onwards with the existance of WWII.

"Coaxial cable" was easily known early except the common name was just "shielded line."  Working out of the electric and magnetic fields took academicians a bit longer to complete.  Remember that Carson had the mathematical relationships of carrier and all sidebands for the three common modulation types way back in 1915.  That was before anyone had any modern-day network analyzers or test equipment of much precision.

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In coiling the line, Guanella intentionally formed a choke, whose conductor was the exterior surface of the coax’s shield. Recall that skin-effect is operative on a coax-shield at radio-frequencies, so the transmission-line current is on the shield’s inside surface and the harmful “common-mode currents” and so-called “antenna-current” is on the shield’s outside surface.
Without Guanella's illustrations or more-meaningful text (?) there's a confusion of basic principles and the APPLICATION.  Yes, basic coaxial cable can be described as "unbalanced."  Wind it around some circular former, with or without any magnetic core material, and one gets the OUTER CONDUCTOR into a reasonably compact structure.  The inductance of the OUTER CONDUCTOR, specifically the reactance at frequency, acts as a high impedance to RF current flow in the OUTER CONDUCTOR.  That is the "choke" (a dummy-simple simplistic term used long, long ago).  The Inner Conductor doesn't care.  The vehicle carrying the RF energy INSIDE the coaxial cable is that TEM field between Outer Conductor and Inner Conductor.

Breaking up the OUTER CONDUCTOR - by itself - as a conductor for other RF couplings seems to be the main task of this sort of classical balun.  Obvious example is a horizontal WIRE dipole fed from coaxial cable.  RF energy goes up in unbalanced coax, the hanging balun does the transformation from unbalanced to balanced and the coax Outer Conductor has little effect on the dipole's antenna pattern.  As long as it is close to right angles from the dipole, that is.  Cheesy

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It is the choke that limits these harmful currents; these currents do cause flux in the core.
As Guanella showed on his schematic, this choke is in parallel with the transmission-line.
This choke serves to isolate the input from the output and so suppresses any conventional transformer current and allows transmission-line current to flow.
So that’s it; we have a 1:1 balun made with an air-core and, in that core, there are no flux-lines from the transmission-line currents.
Since I don't have that schematic I can't visualize what Guanella (or yourself) are trying to say.  What has happened is that introducing this "balun" is simply isolating much of the effect of the outer conductor of the coaxial cable from coupling into some sort of antenna structure or any other conductor in close proximity that may be carrying EM energy.  Whether or not such coupling is "harmful" or "harmless" is a matter of judgement relative to analysis of the "antenna" as a complete structure.  The "box" that does the transformation doesn't really matter as long as the coaxial cable feeding it is - effectively - isolated from any induced currents in coax outer conductor going on to the antenna.
You do need to revise your last sentence above.  You are implying that an AIR CORE INDUCTOR HAS NO MAGNETIC FIELD.  It absolutely does.  If there were none, regardless of core material (air or anything else) there would be NO SUCH THING AS L-C RESONANCE!  With air-core inductors, the magnetic field is spread out more and is thus affected more by shielding materials, thus increasing inductive losses and lowering Q.  With toroidal cores the magneitc field is much more concentrated within the core and Q is least affected by shielding conductors.
 
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4b. The seminal work by Joe Reisert W1JR in 1978 enhanced the 1:1 balun idea further by winding that coil of coaxial transmission-line on a toroid-core. Here also, by virtue of the coax’s inherent shielding feature, we certainly can see there are no flux-lines introduced into the toroid-core when just balanced transmission-line currents are flowing.
Using the word "seminal" is a bit too "Hollywood" here.  Look the word up.  The word "seminal" could apply to Claude E. Shannon's 1948 paper from Bell Labs on the relationship of signal strength, noise, and information rate that became a standard "Law" in ALL communications.  It's known as "Shannon's Law" elsewhere in electronics but Newington doesn't like to print that much.

In 1973 I was working at an RCA Corporation division in Van Nuys, CA.  That division made several different things, among them "SIDs" or "Seismic Intrusion Devices."  Last generation of them to be used in the Vietnam conflict.  The task was to satisfy a high brass question as to whether the low-VHF antenna pattern was "different' when buried compared to when just laid on the ground or at an antenna range.  I was elected, got a technician, had to collar the company gardner to "supervise" digging at the far reaches of the company lawn.  This was on such short notice that all I could gather was some spare RG-174 coax to couple to a VHF Field Strength meter, H-P 608 generator at various heights with a whip antenna as illuminator.  The lawn was uniform, all buried sprinkler pipes plastic.  To break up the effect of RG-174 outer conductor from any effect on antenna pattern, I just wound it around some cardboard mailing tubes (maybe an inch+ in diameter), secured that with cellophane tape.  Yes, I later measured the inductance formed, included it in the report along with everything else done.

Note the time difference: Five years.  What I did earlier was "common knowledge" among those of us who had to play with RF.  Winding coax to make a "choke" in the outer conductor wasn't even a question technically, nor worthy of a patent (it was "prior art"), and we didn't think much about it.  Does winding any conductor around a powdered-iron core increase its inductuance?  Of course it does.  We didn't need to get that fancy for that test.  Interestingly enough, a couple of the other engineers were constructing a solid-state PA out of one of Helge Granberg's first Motorola AppNotes, playing with very strange-looking "RF Transformers" that looked more like foreshortened transmission lines.  Micro-Metals and Fair-Rite were producing core material products and doing good business then, still are.

I went to the two Reisert links you provided.  Both were to (essentially) catalog pages for Balun Designs LLC and the one interior photo of each page couldn't be expanded for clarity.  Neither link showed anything about "ways of winding coax around a toroid."  This was a time when Bill Amidon's display racks of iron-powder core products from Micro-Metals were in nearly every electronics store selling radio parts in the USA.  I don't mind advertising but using it as a "reference" for how-to-make-it information is a tad cheap.

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... Notice the plastic jacket has been taken off the coax leaving the shield exposed; easier to wind and can put on more turns.
If that bared Outer Conductor shorts with other turns of the Outer Conductor, then there is the danger of good old "shorted-turn effect" that has been with all coils and transformers since day one.
The inductance lowers, "choking" effect is less because the inductive reactance is lower.  There MUST be some insulation between turns of that Outer Conductor.  Perhaps not as thick as the supplied jacket material but the Outer Conductor MUST be insulated from adjacent turns.

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4d. Another ingenious style “current-balun” is W2DU’s beaded-balun, where coax-cable is passed through ferrite-beads to form chokes ; although simple in concept, proper core permeability choice is needed to prevent cores from breaking due to excess heating of the cores.
Ingenious yes, practical not so much due to cost of core material in the proper sizes.  It has been done on RF PCB structures of stripline/microstrip for decades...even with rectangular pieces of ferrite.

I must ask where this "excess heating of the cores" comes from.  It is usually the case that the most RF energy is contained WITHIN the coaxial cable, in the TEM field doing the propagating out to the antenna.  The only RF radiation OUTSIDE of the Outer Conductor is due to physical construction of the coaxial cable's outer conductor, how much "RF leakage" it has...a typical specification for an urban cable TV system (insofar as the FCC is concerned).  Such "RF leakage" is typically 40 db down, usually farther down with foil-wrapped braid of the Outer Conductor.  If 1 KW RMS RF is going through the coaxial line, a 40 db "RF leakage" would put only 100 mW RMS RF outside the Outer Conductor.  "Heating" of a piece of ferrite material or powdered-iron material the size of a 1/10th Watt resistor?

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5. A different 1:1 balun is a “Ruthroff-balun”; named after its Bell-Labs inventor in 1959.  Another name for the “Ruthroff-balun” is “voltage-balun”.  As I see it, the voltage-balun generally is inferior to the Guanella-balun.
You still haven't explained this alleged "INFERIORITY" of the Ruthroff balun, which seems to me to be just an ordinary wideband RF transformer.  Ruthroff did a number of papers on wideband RF transformers.  They just weren't published much by the ARRL.  Cheesy

Technicially or practically, I don't see the difference (or the alleged "inferiority") of using some integer-ratio-of-winding-turns wideband transformation device as long as the frequency span of the device itself is sufficient for an application.  Right now I'm using some Mini-Circuits wideband transformers good for 60 KHz on up to 40 MHz.

Some of Ruthroff's other published articles included specific "bifilar" or "multi-filar" transformers using wire stock extruded with multiple wires.  This made it easier to achieve specific winding turns in difficult-to-reach, small cores, good for toroids with their smaller center hole.

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8b. Concerning a transmission-line, the US-Army manual TM11-675 (Aug 1951) has that “…the greater portion (about 90%) of the transmitted energy is in the electromagnetic waves that the line conductors guide through the space between them. In general, less than 10% of the transmitted energy is actually in the conductors of which a well-designed line is comprised.”
  (Comment by KM3K: I have not seen these statements anywhere else.)
In my time I've seen an enormous number of USA military TMs and MIL-SPECS, while in the military and as a civilian.  I don't recall that particular one since my military schooling did not include such "textbooks."  In fact, NONE at all at Signal School at Fort Monmouth in 1952.  Cheesy

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8c. In a transmission-line, there are two conductors (spaced as in two-wire-line or as in coax).
There is an electric-field between the two wires.  Each wire has its own magnetic-field.
These fields are related in a way that only the Divine Creator fully understands but Heaviside, drawing on Maxwell’s work, was able to express mathematically and we are not going there at all.
Sorry, but you just admitted NOT UNDERSTANDING fields and waves.  You can't double-talk your way out of neglecting the magnetic field component.  It is THERE.  If you really and truly venture into that area of EM you can find at least two dozen different field arrangements which are known, identified, were published long ago.

Note:  The fields (both electrostatic and electromagnetic) are different between two-wire "balanced" lines and coaxial "unbalanced" lines.  Look it up.

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For two-wire-line, the energy is confined to the immediate region around those wires.
For coax, the energy is confined between the center-wire and the shield (assuming a good shield).
The electromagnetic signals we will be using will be Transverse-ElectroMagnetic (TEM) waves; that is, the standard HF and VHF ham-band stuff.
How about UHF ham-band stuff?  Will they work outside of ham bands?  Cheesy

The above is okay as an introductory speech on a lesson "transmission lines for dummies."  However, a few of us have been around for a while and actually worked with lots of frequencies using all sorts of transmission lines in professional (including military) radio, some of us being members of a local PGMTT, some of us knowing what a "slotted line" is, some of us knowing what a "bolometer mount" is, some of us all too familiar with a "415" or a "430" or a WGBCO attenuation standard or the great number of fields possible in a tuned cavity, or what Emerson & Cuming produce or Teflon PCB stock or one "bible," "Matthei" (McGraw-Hill's enormous old text by Matthei, Jones, Young) or the now-out-of-print Schaum's Outline Series "Transmission Lines" by Robert A. Shipman (excellent technical book on transmission lines from 50 Hz to 5 GHz).

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10. In his seminal ARRL 1985 article, Roy Lewallen W7EL introduced the terms of “current-balun” and “voltage-balun”. Here is a link; it is a good read…. http://www.eznec.com/Amateur/Articles/Baluns.pdf
Both baluns work by the transmission-line mode.
The current-balun (Guanella) puts equal current into/out-of its output terminals; highly desired feature.  The voltage-balun (Ruthroff) puts equal magnitude voltages at its output terminals.
Whoops...there's that "seminal" thing again.  I admire Roy Lewallen's writing, clear and concise and able to convey meaningful thoughts.  In all fairness to Roy's work, a good description of what exists is not "seminal" in that it introduces new concepts such as Shannon did with his earlier "Law."

BTW, according to the link, Roy put "voltage balun" and "current balun" within quotes and did not attempt to "introduce" them.  That indicates the terms were already in-use, dumb as I think those terms were on electronics principles.  I don't like the word "choke" either, it being so 1920s style when even some academics weren't sure of what they were talking about.

But I'm still not convinced that the so-called transmission-line form is "highly desireable" until there is some COMPARISON data.  Take apart some Mini-Circuits wideband transformers and you might just see some "UNDESIREABLE" structuring, yet they test out just fine.

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11. It is important to comment on the impressive frequency range of a well-designed current-balun.
Why can't you comment on the "impressive frequency range" of a well-designed "voltage-balun?"

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Earlier in this reply, I provided a link to a toroid wound with coax; that commercially produced 1:1 current-balun at 50-ohms, wound on a toroid-core with coax, has a passband from 1 to 54 MHz with very, very low insertion-loss and very high choking-impedance.
Yes, a nice advertising page from Balun Designs LLC in Denton, TX, bossed by Bob Rumsey, KZ5R.  I'd give the exact part number but I think you will fill that in for more free advertising.

[This is Part 2 of a reply...Part 3 follows - LHA]
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K6LHA
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« Reply #25 on: July 11, 2010, 02:03:33 PM »

[This is Part 3 and last of the series of the same reply - LHA]

12. Moving energy in a balun from input to output by the transmission-line mode on a toroid-core means that theoretically there is no flux in the toroid-core.
Now, in actuality, because we cannot make a perfect transmission-line, we can expect there will be some accidental flux but nowhere near the magnitude from a conventional transformer.
It is easy to understand why there is no flux for well made coaxial-cable.
But it may not be so clear for two-wire transmission-line.
So here is why there is no flux in the toroid-core for a theoretical two-wire transmission-line:
  a) the current in each wire is equal but going in opposite directions; should be 180 deg out-of-phase.
  b) this means the magnetic-fields caused by those currents are also opposite and cancel each other out everywhere except in the very immediate region between the two wires.
  c) because the magnetic-fields largely cancel everywhere, there is no net flux in the core, which in turn means no concerns about core saturation and all the problems that can bring.
Whooo!  Big mix-up on basic theory there.  For example, if "there is no flux in the toroid-core" (meaning magnetic field), why USE a toroidal core?  I'm not talking perfection of things here, I'm talking basics of BOTH electric and magnetic fields.  Think on it.  WHY use that torus at all if there is NO magnetic field?

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This problem is covered at length in the 2007 ARRL Antenna-Book.
Those who want to pay LESS for ARRL publications should check out Amazon.  One can get lots of them for two-thirds the ARRL list price.  No sales tax to pay.  With an Amazon gift card I bought the 2010 ARRL Handbook for $33.50 instead of paying $50 List and had no shipping charges from Amazon.

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b) drive balanced antennas (e.g. dipole or yagi) with equal currents.
Note:  Drive them with equal current AMPLITUDES but opposite phase.  Small note but important.

The old US Army AN/TRC-1 (low VHF) and AN/TRC-8 (higher VHF) radio relay Rx and Tx operated into Yagi-Uda 3-element parasitics (TRC-1) or square-corner reflectors (TRC-8) with totally UNbalanced coax cable feed.  The outer conductor of the coax went directly to the other half of the dipoles (as well as the rest of the antenna conducting structure) and I never saw any reports of "badness" about them due to this terribly UNbalanced operation.  Both were horizontally polarized.  Control Center in Tokyo outskirts at at least 80 or so separate-feed antennas on its roof.  Those went into service in 1943-1945 and remained in-use until after 1960 and post-war frequency allocations changed for lots of nations.

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Len, I could email to you the plot, from Sevick’s book, which shows the superiority of the balun over a conventional transformer; your email-address is hidden; mine is there, so let me know by email if you’d like the plot.
My apologies for not keeping the new Eham software record-keeping updated.  My mail alias is LenAnderson@ieee.org   No thanks on a plot copy, regardless of the alleged "superiority."  Cheesy

By the way, using a balanced pair of wires as a "current balun" basic element, you might check out a few things for yourself.  Firstly, the length of this wound transmission line insofar as lowest frequency is concerned WITHOUT any influence of the core material on coupling; it might be surprising.  Secondly, how does the characteristic impedance of this balanced line affect performance insofar as spacing from the adjacent turns?  As part of that how is that same characteristic impedance act when the core (of any kind material) is close within the field of the wound line?  I hope you didn't think that two wire pairs acting as transmission lines were "coupling free."  They aren't.  Been a whole lot of couplers, including directional couplers, built since the 1940s that work fine with unbalanced lines designed with deliberate coupling.  Even on stripline/microstrip.  Been there, done that.

73, Len K6LHA

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KM3K
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« Reply #26 on: July 12, 2010, 07:20:15 AM »

Hello Len K6LHA,

Apologies that I couldn’t convince you of the real-world facts.
At this point in time, I think I’d have trouble convincing you that the world is round. Smiley

When I read you turned away my offer to send to you an extremely significant plot, well, that made me realize it is time to give up.
For me, it is just too tiring to debate so many pointless objections through these postings.

We might have had a substantive discussion about what I feel Dr. Sevick left unanswered.

Concerning the admonitions:
a) to revise what I wrote, let me use a biblical sentence, “What I have written, I have written.”
b) about supplying links to a commercial site; frankly, I took offense at the wording.
Those happened to be the ONLY sites which, after much web-searching, I could find that had photos detailing what I wanted to show.

I truly, truly believe that you would be better served to study both books by Sevick about baluns and ununs.
I would urge any interested person to either get them through a local-library or buy them (I bought mine “used” thru one of the Amazon choices) towards getting a handle on these concepts.
Here in my county in Pennsylvania, we have a program called “Inter-library Loan”, through which one can obtain books not held by the county-library-system.
It was through this program that I originally obtained both of Sevick’s books and then realized I wanted to have my own copies.
I caution that his book “Transmission-Line-Transformers” is up to the 4th edition; the 1st edition should be avoided as Sevick did a big re-write on it.

Perhaps you might consider writing your very own book on how you think baluns work.
After all, as Dr. Sevick (PhD in Applied Physics from Harvard) said, “….For those who disagree with my views, designs, or recommendations, I encourage them to …put it in writing. Then we will all benefit from the new information.”
Too bad he is no longer here to read what you’d write.

73 Jerry KM3K
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AA4HA
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« Reply #27 on: July 12, 2010, 10:22:29 AM »

There are several examples where a high Z receiver is attached to a low Z feedline;

Television sets that had a 300 ohm balanced connection to convert it into 75 ohm unbalanced.

Many military receivers like the SP-600 (100 ohm) or the R-390 (125 ohm) where a balanced connection is provided at the receiver. To do it right you would use a unbal to convert that over to a 50 ohm feedline. There just are not that many places where you can buy 100 ohm twinax any more.
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Ms. Tisha Hayes, AA4HA
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K6LHA
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« Reply #28 on: July 12, 2010, 11:44:38 AM »

Hello Len K6LHA,

Apologies that I couldn’t convince you of the real-world facts.
At this point in time, I think I’d have trouble convincing you that the world is round. Smiley

Try not to start some personality-conflict "fight" over subjects that have been scientifically and practically proven years ago.  Evangelism over the teachings of one guru don't have any place in communications, certainly not in the limited EM area of HF.  That part of the EM spectrum is where I started in 'radio' in early 1953.

Yes, I do believe the earth is round.  I've seen the films and, later, video, from NASA sources, talked to NASA people (including two astronauts, Young and Crippen), and a LOT of PhDs (dozens, many more than one).  I'm not swayed by Title, Rank, or whatever honor is bestowed by others that I "should honor" certain "significant persons."  I believe in reproducible RESULTS explained in a clear manner with all test data presented for all.

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When I read you turned away my offer to send to you an extremely significant plot, well, that made me realize it is time to give up.
Let's put it this way...ONE PLOT of something, anything, isn't enough to convince me or anyone (with knowledge of known basics and some experience) that something is "better" just because it is presented by a BELIEVER.
Sorry, but that is just Bible-thumping religious evangelism.  It isn't science, it is just an act of faith.  Electrons, fields and waves don't obey human faith.  They obey only Laws of Physics, their own.  You have to learn those in order to make 'radio' hardware and then make that hardware work.
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For me, it is just too tiring to debate so many pointless objections through these postings.
You are letting your emotions get the best of you.  That doesn't work in any paper presentation.  That doesn't work on the bench.  That doesn't work in presentations before others, many of whom will probably have a great deal more knowledge and experience on a subject than you have.  That doesn't work on demonstrating hardware capabilities in environments you've never been to, such as other electronics locations where you must show reproducible results by on-site testing or performance.
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We might have had a substantive discussion about what I feel Dr. Sevick left unanswered.
No, "we" would not.  When you can't accept certain long-known Basic Facts about fields and waves, such as some magical "disappearance" of a magnetic field because someone else said so, then we can't have any "discussion" at all.  KNOWN technical basics have to be observed in "discussion" and the writing of same must be clear and unambiguous to convey something new.

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a) to revise what I wrote, let me use a biblical sentence, “What I have written, I have written.”
Okay, what do we simple mortals use, the Bible?  The Quoran?  The Talmud?  Should we know erect temples and idols and worship those "who have written?"

Fella named Erich von Daniken, a Swiss, wrote five books all about "explaining" how "ancient astronauts visited earth" long, long ago.  We don't have Time Machines to prove it.

A couple of then-respected and titled physicists once wrote a paper about "Cold Fusion" that was supposed to be a new principle in physics about extracting energy.  Problem was, this "cold fusion" wasn't Reproducible.

You've quoted ONE author on one particular subject and almost demand I BUY that book "to see the light."  That's the inference of ARRL publications and a quasi-religious manner of SELLING which isn't in the spirit of a hobby pursuit regarding a technologically-based activity.

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b) about supplying links to a commercial site; frankly, I took offense at the wording.
Those happened to be the ONLY sites which, after much web-searching, I could find that had photos detailing what I wanted to show.
Then you should have done the following:  (1) State clearly, unambiguously, that it is an advertising page; you did not.  (2) Make one, take pictures of it, post those.  (3) Show pictures of such a transformer that another amateur has and explain that they own it and use it.  (4) Show a bench test set-up, name the test equipment, explain how the figures were arrived at along with possible errors due to calibration uncertainties.

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I truly, truly believe that you would be better served to study both books by Sevick about baluns and ununs.
WHY?  Just because I don't agree with your topic subject, I am considered "ignorant" of anything else that has been used for impedance transformation at RF - or any frequency?  I will take that as a blanket condemnation of my own experience, knowledge.

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Perhaps you might consider writing your very own book on how you think baluns work.
No.  I would be just re-writing WHAT IS ALREADY KNOWN.  The subject isn't worth 100,000 words between covers along with illustrations that are meaningful.  What I have written professionally on technical subjects is carefully done, researched, without any ignorance of basic theory, has already been peer-reviewed and checked for errors.

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After all, as Dr. Sevick (PhD in Applied Physics from Harvard) said, “….For those who disagree with my views, designs, or recommendations, I encourage them to …put it in writing. Then we will all benefit from the new information.”
Too bad he is no longer here to read what you’d write.
Excellent selling point to "validity" - quote someone with a Title who is already dead.  Bad, bad form to speak ill of the dead, right?  By transference, you identify with Sevick, therefore not congratulating your topic posting is therefore speaking ill of someone you are quoting. 

That's an old literary trick that I've seen way back in ARPANET time, well before USENET and the Internet.  I can go grab my Bartlett's Familiar Quotations (softcover) and sort through it for applicable quotes to use on my posts, right?   Grin

K6LHA
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K6LHA
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« Reply #29 on: July 12, 2010, 11:55:05 AM »

There are several examples where a high Z receiver is attached to a low Z feedline;

Television sets that had a 300 ohm balanced connection to convert it into 75 ohm unbalanced.

Yes, only a few tens of millions of those TV receiver baluns made.  :-)

To try to get back to the original topic, any PASSIVE device, a simple device, will work the same forwards or backwards.

A relatively narrowband passive device such as a "rat-race" hybrid, made entirely out of transmission line, never had any sort of (typical) transformer in it, was in the borderline of a Network..  Worked okay for full-duplex operation if the Rx and Tx had their own filters.

73, Len K6LHA
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