There is much mythology in the summary quoted below.
A high SWR at the feed line is not an indication of poor performance as
long as the antenna tuner provides a good match to the transmitter. A
high swr merely indicates the the antenna/feed line is showing an
impedance other that 50 ohms. The reflected power is not lost unless
the transmission line losses are high. The power is mostly reflected
back toward the antenna and does not heat the tuner. Many excellent
antennas operate at design impedance's of 400, 600, or higher, ohm
The conclusion that High SWR indicates a high loss in the tuner is
wrong. If the impedance is very low the resulting high current may cause
I squared R heating. Otherwise the losses in good (and properly tuned)
tuners are quite low.
Like wise, the concept that low SWR at the end of the feed line
indicates a good antenna can be wrong. An end fed half wave has
extremely high impedance. When properly matched it can be extremely
efficient. By the way, both a dummy load and a very long piece of coax
may indicate a 50 ohm "match" even if the antenna is broken, due to
losses in the feed line.
I do agree that that if an antenna is designed for a 50 ohm impedance
and your swr changes from 1.5 to 1 to something greater than 2 or 3 to 1
then something is broken. The Carolina Windom is not 50 ohms on all
bands. But when properly matched with a tuner, it can perform well.
The concept that an antenna must be resonant is also a bit of folklore.
Various non resonant lengths of wire work nearly as well as a resonant
dipole when properly fed with a low loss feed line and tuner. They have
the advantage of working well on several bands without lossy traps and
extra wire. Dipoles do not work well on the second harmonic.
By the way, the characteristic impedance of a dipole with good height is
70 or 100 ohms. With a good low loss feed line the SWR at the shack
might be about 1.5 to 1. A higher loss system might show close to 1 to
1. So if you have this situation, use it and enjoy. Obsession about
1.01 to 1 SWR is of no use. If your transmitter is happy running full
power out into a 2 to 1 SWR, relax and enjoy. Some rigs start folding
back at about that level so you want to match well enough to avoid
foldback. It has been widely assumed by too many people that anything
other that 1.1 to 1 is unacceptable. 1.5 to 1 might be indicating an
optimal low loss setup!
Post by Glenn Maclean
Thanks to all who replied to my watt meter question. I had numerous answers.
Thank you to all. If my understanding is correct this is what is going on.
The KAT100 automatic tuner is doing exactly what it is suppose to do. It is
making the KPA100 finals (tank circuit) happy with a 50 ohm impedance match
keeping the current and voltage in a satisfactory range. However this does
not mean the antenna is performing very well on some bands. I was able to
see this when the watt meter was connected after the tuner and showed a very
high SWR especially on 30 meters and some of the other bands. When the watt
meter is showing a low SWR the antenna is resonant on those bands and
performing well.. On the bands with a high SWR the tuner is absorbing a lot
of power which means the EFR (effective radiated power) at the antenna is
Thanks again to all who replied,