Now available: Program COAX_VLF
The behaviour of transmission lines at the lower frequencies is more complex than it is at HF and above. The effects set in sooner at higher frequencies on low impedance coaxial transmission lines. They are affected more at higher frequencies than other types of line.
As frequency is reduced below several hundred KHz the impedance Zo increases, its impedance angle becomes more negative, and the propagation velocity decreases. Unusual things happen such as reflection coefficients being greater than unity and the SWR being greater at the input end of a line than it is at the load end.
At power and audio frequencies Zo can be an order of magnitude greater than the nominal HF value, and the angle of Zo aproaches -45 degrees.
It is useful to be aware of the magnitude of such effects. With coax they can be experienced in small ways at frequencies as high as 2 MHz or more.
Download program COAX_VLF in a few seconds from website below and run immediately. Filesize = 48 Kilo-bytes. It is both practical and educational. Try to fathom out how reflection coefficients greater than unity can arise.
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