On 2/6/2025 6:07 PM, Lukasz wrote:
So could someone please explain or point me towards some books/articles
that talk about what happens exactly with voltages/currents at bad SWR?
What you need to study is "Transmission Lines." If you are comfortable
in English, the ARRL Handbook and something like that from RSGB are good.
The ARRL Antenna Book goes deeper, and comes with a very nice (but very
simple) app that computes SWR, loss, voltage and current along the line,
and graphs voltage and current. The app is TLW. It's a very nice
learning tool.
There's also TLDetails, a simple free Windows app by AC6LA, that
computes loss, SWR, and complex impedance at one end of a line for
complex impedance entered for the other end. It computes and plots the
variation of Zo, loss, and velocity factor with frequency.
https://www.ac6la.com/tldetails1.html
AC6LA also published ZPlots, a freeware Excel spreadsheet which does
that and more. It runs ONLY in Microsoft Excel, not in clone
spreadsheets. One of its most useful tools is the ability to compute the
fundamental properties of some unknown transmission line from swept
impedance measurements of a known length.
https://www.ac6la.com/zplots1.html
Nearly all texts for radio uses of Transmission Lines treat Zo and VF as
constants for all frequencies, but they're not. To understand why, and
how they vary with frequency, study my tutorial about that.
http://k9yc.com/TransLines-LowFreq.pdf
And this Q & A about Transmission Lines and stubs, which is why we need
"big" transmission line for low loss.
73, Jim K9YC
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