RadioBanter - View Single Post - An antenna question--43 ft vertical

[email protected] · July 9th 15, 08:44 PM posted to rec.radio.amateur.antenna

rickman wrote:
On 7/9/2015 3:03 PM, John S wrote:
On 7/9/2015 12:40 PM, wrote:
Jeff wrote:
On 08/07/2015 19:14, wrote:
John S wrote:
On 7/7/2015 1:44 PM, wrote:
Ian Jackson wrote:
In message , Jerry Stuckle
writes

Sure, there is ALWAYS VSWR. It may be 1:1, but it's always there.

If there's no reflection, there can be no standing wave. So, being
pedantic, there's no such thing as an SWR of 1:1!

Despite the name, VSWR is defined in terms of complex impedances
and wavelengths, not "waves" of any kind.

Actually, VSWR is defined as the ratio of Vmax/Vmin.

Actually, VSWR can be defined several ways, one of which is:

(1 + |r|)/(1 - |r|)

Where r is the reflection coefficient which can be defined a:

(Zl - Zo)/(Zl + Zo)

Where Zl is the complex load impedance and Zo is the complex source
impedance.

Note that a complex impedance has a frequency dependant part.

Note the the definition of VSWR uses the magnitude of the reflection
coefficient, |r|, which removes the phase and frequency dependant parts.

Jeff

The magnitude DEPENDS on the frequency dependant parts.

But the ratio of Vmax/Vmin does not.

Huh? I'm pretty sure the VSWR is a function of frequency. A great deal
about the impedances *and* the voltages change with frequency.

A simple fact that totally eludes him.

SWR is a quality of an impedance match at a specified point in a system
and at a specified frequency.

--
Jim Pennino