in the article A simple transformer model of the Guanella 1:4 balun – some further observations I stated: Note that a two terminal impedance is a naive representation of many if not most antennas, popular, but a naive over simplification that does not facilitate evaluation of current balance. An example was a recent posting above … Continue reading Modelling an antenna as a simple two terminal resistance is often naive
With the popularity of the nanoVNA, the matter of optimisation of antenna systems comes up and the hoary chestnuts of ham radio are trotted out yet again. Having skimmed a presentation published on the net, an interesting example is presented of an 80m half wave centre dipole with feed line and various plots from the … Continue reading Antenna system resonance and the nanoVNA
A common question in online forums relates to inability to reconcile analyser measurements of an antenna system with the transmitter system antenna facing VSWR meter. The cause is often that the antenna system was changed significantly to connect the analyser. Seeing recent discussion by the online experts of how the measure the impedance of an … Continue reading Antennas – disturbing the thing being measured – open wire lines
The Pawsey Balun (or Pawsey Stub) is described as a device for connecting an unbalanced feed to a balanced antenna. Above is a diagram of a Pawsey Balun used with a half wave dipole (ARRL). Pawsey Balun on an asymmetric load reported model results in an asymetric dipole antenna, and showed very high common mode … Continue reading Pawsey Balun – what is it good for?
This article is a continuing discussion of Radcom Feb 2019 “cable balun”. The article Baluns in antenna systems explores some different dipole and feed line configurations and the effectiveness of common mode chokes at various locations on the feed line. Models 1, 2 and 3 particularly show the effect of a quarter wave vertical common … Continue reading Radcom Feb 2019 “cable balun” – a deeper look
This article describes a Guanella 1:1 current balun which has high common mode impedance (Zcm) and low Insertion VSWR. It is for application on antennas that have low VSWR50 on at least some bands, especially if they would be used without an ATU on some bands. The purpose of the balun is to minimise common … Continue reading A low Insertion VSWR high Zcm Guanella 1:1 balun for HF
A correspondent having read Analysis of a certain dipole animation questioned the validity of the lossy transmission line model of the dipole, citing the case of an OCF half wave which has an approximately resistive feed point. Since the OCF lacks the symmetry exploited in earlier study, we must consider each half of the OCF … Continue reading Analysis of a certain dipole animation – OCF implications
At Yet another dodgy coax collinear I wrote about a design published recently in QST. More recently, a ‘design’ has emerged in eHam forums that appears to be identical. Last update: 27th August, 2015, 12:10 PM
At Efficiency and gain of Small Transmitting Loops (STL) I discussed the use of bandwidth measurement of a small transmitting loop (STL) for estimation of efficiency. Paul Casper (K4HKX) has built a series of STL which he describes on his K4HKX QRZ page. Last update: 17th April, 2015, 7:07 AM
NEC-2 and NEC-4 support a GM card to translate and rotate a structure in three dimensions. This article gives a simple but practical example of exploitation of this often overlooked facility. Last update: 5th December, 2014, 2:44 PM