VE6AB Mobile RF Network
What your seeing here, is the RF Network for the 17 meter segment of my 10-80 meter mobile gearmotor antenna, plotted on the smith chart of my antenna analyzer.
Smith Charts make it easy to check the RF Network of your antenna, and make any adjustments necessary to balance the antenna.
When the antenna is perfectly balanced, the RF network will be centered on the smith chart, and this will indicate a 50-ohm load with little reactance or capacitance.
All initial adjustments to the antenna were made with the analyzer connected through a short length of coax at the feedpoint of the antenna, without the shunt-coil or long length of coax in line as seen here... http://www.jerryclement.ca/HamRadio/HamRadio/i-ttPS9NG/0/XL/6N4A6836-0-XL.jpg