At Baluns – show me the numbers I raised the value of quantitative measurement of the complex common mode impedance of current baluns as a figure of merit for certain antenna applications.
This article shows a simple method of measuring the complex common mode impedance of a Guanella 1:1 current balun using a modern Antenna Analyser.
The instrument used for this demonstration is a Rigexpert AA-600, and its PC client Antscope. Continue reading Measuring balun common mode impedance – #1
A reader of Low power Guanella 1:1 tuner balun using a pair of Jaycar LF1260 suppression sleeves asked whether there is an equivalent Fair-rite core for the project.
Fair-rite part 2643625102 (~$4 each from Element14) is of similar size and also medium µ, but slightly different characteristic to the LF1260. Continue reading Low power Guanella 1:1 tuner balun using a pair of Fair-rite 2643625102 suppression sleeves
Hams talk at length about baluns but rarely in quantitative terms.
A quotation from Lord Kelvin is most appropriate: When you can measure what you are speaking about, and express it in numbers, you know something about it. But when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. It may be the beginning of knowledge but you have scarcely in your thoughts advanced to the state of science.
Continue reading Baluns – show me the numbers
A reader of Why the preference for Guanella 1:1 current baluns for HF wire antennas asked if a similar model can be built for a Ruthroff 4:1 balun.
Hams tend to insist that the Ruthroff 4:1 balun cannot be represented by transmission line elements, but they are quite wrong. Continue reading A SPICE model for a Ruthroff 4:1 balun.
I am often asked why I recommend a Guanella 1:1 balun with high choking impedance for most HF wire antennas over voltage baluns and 4:1 current baluns. This article explores the topic using SPICE models for a voltage balun, 1:1 current balun, and 4:1 current balun. Continue reading Why the preference for Guanella 1:1 current baluns for HF wire antennas
In a QST column in 2008, a correspondent asked the question
… I have the ladder line terminated to double coaxes that run about 12′ (4m) inside the house to an antenna tuner. Should this pair of coaxes be grounded at one end or both ends?
The Doctor gave a detailed diagram (above) and his advice was… Continue reading Spoiling balun action with ‘shielded twin’
A correspondent sent me a pic of a commercial balun asking “How does this balun work”. He explained that it is a “combination 1:4 balun followed by a current choke”.
My first thought was that this is likely to have been a creation of Jerry Sevick… but let’s try and analyse it. Continue reading (How) does this balun work?
Off centre fed (OCF) dipoles are very popular with Hams on HF.
Many claims are made for variations of the theme, but the essential common feature is that the offset feed point provides a feed point impedance that is not too unsuited to 50Ω coaxial feed line at the fundamental resonance of the dipole and half wave harmonics. Continue reading OCF dipoles
There is a common Rule of Thumb that to be effective, the magnitude of common mode impedance of a Guanella current balun in an antenna system should be at least 500Ω (Reisert 1978).
This article proposes a possible origin for this thinking, and discusses the validity of the underlying model. Continue reading Baluns – Rule 500
One sees simplistic application of ohms law to antenna balun problems frequently in online forums, but is the technique valid? Continue reading Using Ohms law on antenna baluns