Tuning: If the impedance is high at 0.67, the ratio is
high. If the impedance
is low, the ratio is low.
Adjust accordingly. Simple!
Advice: Use a choke
balun at the feedpoint. The farther offcenter, the greater the current
imbalance between arms, the more “common mode” current on a coaxial
feed line. Common mode
current problems cause change in tuning if you touch the cable,
sometimes tingling or “bites” to face and lips when transmitting.
RF radiating from the coax can couple with nearby electronics
or AC power lines to affect TV, radios, clocks as well as control
devices like alarms, thermostats and monitors.
Equal, Wide
and Tall LAntennas
The Equal LAntenna
With “equal” arms, the horizontal
arm is slightly longer at resonance due to the effect of ground.
The armtoarm ratio therefore is not exactly 0.5. Impedance is around 40 ohms. SWR can be as low as 1.21.3:1. RF polarization is equally horizontal and
vertical.

The principles of OCF apply
very well for Lantennas.
The Wide or Vertical characteristic
can emphasized by making OCF ratios smaller
or larger.
The Wide LAntenna
As the offcenter feedpoint ratio goes less than 0.5, the Lantenna
becomes wider and the impedance rises towards 50 Ohms. The antenna hears and talks more like a horizontal dipole as the SWR approaches
1:1.
The Tall LAntenna
As the offcenter feedpoint ratio goes greater than 0.5, the LAntenna
becomes taller and the impedance rises towards 50 Oms. It hears and talks more like a vertical antenna as the SWR approaches
1:1.
Based on modeling software,
Figure
3 below summarizes the results as the feedpoint
of an LAntenna is changed by 0.05 (5%) increments around the center 0.50 ratio.
