You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

This is true. The SWR along a transmission does not change however the impedance does. At first this sounds impossible however once one understands that there is an almost infinite number of combinations of R, Xc, and XL that will yield the same SWR it becomes clear. Also resonance is simply the point that Xc and XL are equal and thus cancel each other out leaving a purely resistive component that makes up the impedance. Far too many people think that resonance means 50 ohms exactly. Not so. I have had short low band antennas that were resonant yet had an impedance of only 3 or 4 ohms. I have also had 1/2 wave end fed wire antennas that were resonant yet had an impedance of over 1000 ohms. This is why I like using an antenna analyzer with a 1/2 electrical wavelength of cable to determine just what the actual antenna impedance is that I am dealing with especially if I am making a matching network for it.SWR is only a small indication of what the antenna system is doing. If all you are looking for is minimum SWR than any line length will work as the ONLY time a perfect 1:1 SWR is achievable is when there is zero reactance and the radiation resistance is exactly 50 ohms.

<blockquote data-quote="Captain Kilowatt" data-source="post: 459566" data-attributes="member: 39"><p>This is true. The SWR along a transmission does not change however the impedance does. At first this sounds impossible however once one understands that there is an almost infinite number of combinations of R, Xc, and XL that will yield the same SWR it becomes clear. Also resonance is simply the point that Xc and XL are equal and thus cancel each other out leaving a purely resistive component that makes up the impedance. Far too many people think that resonance means 50 ohms exactly. Not so. I have had short low band antennas that were resonant yet had an impedance of only 3 or 4 ohms. I have also had 1/2 wave end fed wire antennas that were resonant yet had an impedance of over 1000 ohms. This is why I like using an antenna analyzer with a 1/2 electrical wavelength of cable to determine just what the actual antenna impedance is that I am dealing with especially if I am making a matching network for it.SWR is only a small indication of what the antenna system is doing. If all you are looking for is minimum SWR than any line length will work as the ONLY time a perfect 1:1 SWR is achievable is when there is zero reactance and the radiation resistance is exactly 50 ohms.</p></blockquote><p></p>

[QUOTE="Captain Kilowatt, post: 459566, member: 39"] This is true. The SWR along a transmission does not change however the impedance does. At first this sounds impossible however once one understands that there is an almost infinite number of combinations of R, Xc, and XL that will yield the same SWR it becomes clear. Also resonance is simply the point that Xc and XL are equal and thus cancel each other out leaving a purely resistive component that makes up the impedance. Far too many people think that resonance means 50 ohms exactly. Not so. I have had short low band antennas that were resonant yet had an impedance of only 3 or 4 ohms. I have also had 1/2 wave end fed wire antennas that were resonant yet had an impedance of over 1000 ohms. This is why I like using an antenna analyzer with a 1/2 electrical wavelength of cable to determine just what the actual antenna impedance is that I am dealing with especially if I am making a matching network for it.SWR is only a small indication of what the antenna system is doing. If all you are looking for is minimum SWR than any line length will work as the ONLY time a perfect 1:1 SWR is achievable is when there is zero reactance and the radiation resistance is exactly 50 ohms. [/QUOTE]

Top Bottom