Flagpole Tuner & Balun Configuration | Engineering Manual
Field Operations: Correctly Configuring the Flagpole and VDA Feed System
Technical Manual No. 2.2.1
Physics of the Feed-Point
A Greyline 6061-T6 VDA system is an electrical half-wavelength vertical dipole. To maintain a **Sovereign Communication Node**, the antenna must "float" electrically above the ground. Our data indicates that technical operators spend significant time analyzing this feed-point relationship because it is the key to zero-radial efficiency.
The Signal Chain: Coax from Shack → RF Choke → ATU (Remote Tuner) → HF Antenna.
Correctly Configuring the Tuner and Balun
It is a common belief that one must “ground everything.” This is NOT true for the Greyline VDA System. Like a wire dipole in the canopy, the flagpole is a balanced antenna. Both ends are insulated from the ground, and the off-center (OCF) feed point must be provided with a balanced feed.
The Floating Balanced Output
Most modern tuners are unbalanced by design (grounded shield). To achieve a true "floating" balanced output, a 1:1 Current Choke must be placed in the coax directly ahead of the tuner (on the radio side). This ensures no RF returns to the shack and forces the dipole to radiate at maximum efficiency.
PRO TIP: BUILD FROM THE GROUND UP
- Ground Insertion: Thicker wall 6061-T6 section matches PVC length.
- Feed-point Section: Connect Upper Dipole (longer radiator) to the center coax conductor.
- Insulation: Mount the tuner and balun at least 6 inches above ground on a PVC pipe or wooden stake.
Agency & Municipality Support
Configuring a system for a Sheriff, Fire, or EOC department? We provide full architectural briefs and technical documentation for municipal hardening projects.