Start with the operating decision: CHA OCF40 uses an off-center feed position to present useful impedance relationships on several harmonically related bands; the matching network and controlled feed line complete the design.
How the system behaves
A tuner-assisted match on 60/30/17/15/12 meters does not make radiation efficiency or pattern identical to 40/20/10/6. Geometry, height, common-mode control, coax loss, and ground still matter.
The boundary that prevents mistakes
Sweep the exact installed antenna, record R and X where available, keep the integrated choke in the documented path, and compare field results without using SWR as an efficiency meter.
Use this field sequence
Define the exact configuration and intended path, inspect the complete installation, begin measurements at low power, record the result, and change one variable at a time.
Source boundary
CHA OCF40 User Guide 250513. Use the exact current configuration, components, feed, support, geometry, power, and safety limits; mechanical fit does not establish compatibility.
