An example of the utter nonsense posted on social media.
My very first posting as a trainee was to Bringelly HF receiving station in 1970. It had Rhombic antennas every 30° of the compass, and a few other antennas, but the mainstay of operation was the set of Rhombics.
The nearby transmitting station at Doonside had a similar antenna arrangement of Rhombics fed with two or four wire open transmission lines to transmitters in a central building, for most operations, no coax involved between transmitters up to 30kW and antenna feed points.
Rhombics are an example of a non-resonant antenna, these were used for a large set of operating frequencies that were not harmonically related, were changed through the day with varying ionospheric conditions over the various circuits, within the broad frequency range of the Rhombics, and not restricted by a requirement for ‘resonant length’ of radiator conductors.
You do not have to look hard for other examples of non-resonant length radiators that have good radiation efficiency.
Yet hammy Sammy thinks that ‘resonance’, whatever it means, is a necessary condition for radiation efficiency.
In this case, the quote speaks to the credibility of the author.
Social media and errors
A further disadvantage of lots of social media platforms is the inability to edit mistakes. For example, one poster wrote in the same thread:
The qualitative conclusion here is that a “wild” impedance value of 890 – j418 which is far from resonance can and does yield an acceptable SWR.
My calc is that wrt 50Ω, that example has VSWR=21.7. We all make mistakes, but this appears locked in for perpetuity.
From the same thread:
The ONLY position on the (Smith) chart where resonance occurs is dead center or “bull’s eye”.
So, that depends on your meaning of resonance, and resonance of what? If you accept that X=0 is a requirement of resonance, then it is relevant that in the frame of reference being the Smith chart space, there is line from one side of the the Smith chart to the other where X=0, an infinite number of points of ‘resonance’.
And of course it is unsociable to call out factual error on social media.
Read widely, question everything.
So what happened to Bringelly and Doonside?
Bringelly part of the new western Sydney airport and Doonside is a major road interchange (the Light Horse Interchange).