http://elecraft.85.s1.nabble.com/BL2-Antenna-Balun-Usage-tp7630889p7631058.html
Even Jasik, ed., "Antenna Engineering Handbook" mentions the balun. My
> PLEASE ignore all of Jim's pontification.
>
> I find it curious that Terman ("Radio Engineering"), Kraus
> ("Antennas"), Johnson ("Transmission Lines and Networks") all use the
> "meaningless" word "balun" in their books. Clearly, these guys should
> have consulted with Jim before doing so, because obviously they didn't
> know what they were talking about.
>
> A transmission line transformer can be as simple as a geometric mean
> quarter-wave line between two different impedances. No ferrites
> required. A balun (pardon me, I'm with Kraus) can be a quarter-wave
> open stub at the feedpoint of an antenna. Collins ("Fundamentals of
> SSB") calls this a "Bazooka-type balun", but what does Collins Radio
> know about anything?) Or, it could be a half-wave line connecting the
> two halves of a dipole. A stub balun can be both a balancing device
> and an impedance transformer at the same time. And it's nothing but
> coax. A two-wire line wound around a core might be a common-mode
> choke, but if it's long enough and different in impedance from the
> load, then it's an impedance transformer too.
>
> In summary, just removing the term balun from one's lexicon doesn't
> simplify anything.
>
> And I almost forgot, that N6BV article Jim mentions is titled, "Don't
> blow up your BALUN."
>
> Wes N7WS
>
>
>
> On 5/22/2017 2:11 PM, Jim Brown wrote:
>> On Mon,5/22/2017 12:42 PM, Bill Leonard N0CU wrote:
>>> I am no expert when it comes to baluns
>>
>> You're not the only one. :)
>>
>> Some important comments. First, PLEASE strike the word "balun" from
>> your vocabulary. It is a meaningless word that tells us NOTHING about
>> the device or circuit element it is used to describe. I can think of
>> nearly a dozen VERY different devices that are CALLED baluns. Use the
>> word "balun" conceals what the device actually is and prevents
>> everyone involved from understanding what it does.
>>
>> A two-wire line wound around a ferrite core forms a COMMON MODE
>> CHOKE. It is not a "transmission line transformer," nor is it an
>> inductor, nor is it a transformer at all! The ferrite core carries
>> only flux due to common mode current, and loss in the choke is I
>> squared R, where I is the common mode current and R is the resistive
>> impedance of the common mode choke.
>>
>> Arrays of common mode chokes CAN be wired in series/parallel
>> combinations to match circuits of differing impedance, but that
>> device is NOT a transformer, it is an array of common mode chokes. If
>> we want to know how this array of chokes work, we must analyze them
>> as arrays of common mode chokes, not as a transformer.
>>
>> A transformer, is, by definition, two windings that are magnetically
>> coupled, and the impedance transformation ratio is the square of the
>> turns ratio. If we want to know how a transformer works, we must
>> analyze it as a transformer. It's as simple as that. The ferrite core
>> carries ALL of the flux, and thus all of the differential power
>> carried by the circuit into which it is inserted.
>>
>> In general, common mode chokes do NOT affect the differential signal,
>> but there CAN be differential mode loss in the transmission line that
>> forms the common mode choke due to transmission line effects. For
>> example, if the common mode choke is inserted in a badly mismatched
>> transmission line, there can excess loss due to SWR throughout the
>> line, both in the part of the line that forms the choke and in the
>> rest of the line. Below UHF, virtually all loss in real transmission
>> lines is due to I square R; if the combination of the antenna and the
>> line places a current maxima at the choke, that segment of the line
>> can burn a high fraction of the transmitter power, greatly reducing
>> the transmitter power that gets to the antenna and overheating (and
>> frying) that segment of the line. N6BV wrote an excellent
>> applications note about this for QST several years ago, to which I
>> contributed.
>>
>> It IS practical to model (predict) dissipation in a common mode choke
>> using NEC. A single wire is added to the model with the geometry and
>> physical connections of the transmission line, and the known
>> (measured) impedance of the choke is added as a Load at the point
>> where it is inserted in the system. NEC is then set to model with a
>> defined transmitter output power (for example, 1,500W), and currents
>> are computed. NEC then provides a readout of current at every point
>> on every conductor, and the current in the choke is used to compute
>> dissipation in the choke.
>>
>> Tutorials at k9yc.com/publish.htm show a practical method for
>> measuring the common mode impedance of ferrite chokes, and for
>> determining values for a parallel equivalent circuit that can provide
>> a good first approximation of dissipation.
>>
>> 73, Jim K9YC
>
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