[Elecraft] 9:1 Balun AND "random antennas"

[Jim Brown]

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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