Lets go back to that original post for a second. 'Tuned for the lowest/best SWR?', really? Okay, but that's just half of tuning an antenna, and not the most important part anyway...
I included that note just to indicate that I did what I was suppose to do with the antenna itself, and there was little in that regard that I could do to improve things
Adjusting the antenna for minimum SWR is as good as any other method
of adjusting it, and better than some alternatives. If the SWR is low then
the system must be close to resonance at that point, since you can't have
a low SWR in a 50 ohm system with high reactance. And since the reactance
changes with frequency faster than the resistance, the point of minimum
SWR will be very close to resonance.
You'll still find a few misled diehards who insist that you tune it for zero reactance
rather than minimum SWR. Let's see where that leads...
Let's say we have a 20m vertical with a 5uH loading coil inserted 6' above
the feedpoint, and we are adjusting the length of the upper section above
the coil for resonance at 14.1 MHz. My EZNEC model suggests a total
length of 11.21 feet, with a input impedance of about 30 ohms or so
depending on the ground loss. That's tuning the antenna for zero
reactance at the desired frequency: where is the minimum SWR? At
14.1225 MHz, if you have a very precise meter. But the SWR curve is
very flat: the SWR at resonance is 1.67 : 1, and it is less than 1.7 : 1
from 14.06 to 14.190 MHz. A shift of 22kHz just isn't going to make
any practical difference in the real world.
But who wants to lay flat on the ground to take measurements right
at the feedpoint? That's not very comfortable. So let's say you add
a short coax jumper - say 5' long - between the feedpoint and the
antenna analyzer or SWR meter. If you tune the antenna for minimum
SWR you get the same reading. But if you are looking at the reactance
on an SWR analyzer it now looks like +20.7 ohms, even though the SWR
hasn't changed. Now if you adjust the antenna length or X = 0 you end
up with an antenna length of 10.925 feet, a difference of over 4". Worse
yet, the SWR at that point is 2.68 : 1. Why would you want to tune
the antenna to that setting?
Adjusting the antenna for minimum SWR is easy and it works regardless
of the length of coax cable. Don't believe those who try to tell you