EFOC29 Antenna Installation Guide

Check the Complete Kit Before Installation

The current EFOC29 coax-counterpoise package uses a 29 m radiator starting dimension, approximately 26 m of EXTRAFLEX-BURY-7 coaxial cable and two large ferrite chokes. The cutting machine intentionally supplies extra antenna wire, so the delivered stock must be measured before it is marked, folded or cut. The radiator, transformer, coax return section, choke placement and final feed-line route work together. Changing one can move the impedance, current distribution and pattern.

• Inspect the wire, coax jacket, connectors, transformer enclosure, strain relief and ferrite cores before raising anything.
• Provide independent mechanical strain relief. RF connectors and the transformer enclosure are not suspension hardware.
• Keep the planned wire, supports and every conductive tool far enough from power lines that no part can touch a line—even if a support, mast or wire falls.
• Choose a route that keeps people and animals away from high-voltage wire ends and the feedpoint while transmitting.

Choose the Geometry That Fits the Site

The dimensions below are installation starting points for wire measured from the deliberately oversize supplied stock. Nearby conductors, soil, height, slope and the coax route can change the final tuning. Preserve extra wire until the antenna has been measured in its finished position.

Flat top

• Radiator: begin from the measured 29 m dimension in a straight horizontal span.
• Feedpoint height: approximately 7–18 m.
• Use it when: the site provides a long clear span and the desired coverage benefits from a predominantly horizontal layout.

Inverted L

• Radiator: approximately 26–28 m, with about 7–12 m vertical and 15–20 m horizontal.
• Feedpoint height: approximately 7–18 m; keep the bottom of the vertical section roughly 3–5 m above ground.
• Use it when: a mast can provide useful vertical rise but the rest of the wire must continue toward another support.

Inverted U

• Radiator: approximately 25–28 m, commonly 6–10 m on each vertical side with 10–16 m across the top.
• Feedpoint height: approximately 5–7 m.
• Use it when: two supports are available but the full wire cannot be stretched as one straight span.

Sloper

• Radiator: approximately 27–29 m.
• Feedpoint height: approximately 7–18 m; keep the low end roughly 4–5 m above ground.
• Use it when: one high support and one safe lower anchor make a sloping wire the cleanest installation.

Build the Intended Coax Return Section

Route approximately the first 12 m of coax from the feedpoint as the deliberate exterior-shield return section. It may run horizontally, follow a gentle zig-zag or lie near the ground when the site demands it. Slight elevation can reduce ground coupling, while every route changes the installed RF circuit.

• Keep this section at least 10–20 cm away from metal roofing and other large metal surfaces where practical.
• Avoid tight coils, sharp bends, crushed cable and repeated flexing at the connectors.
• At approximately 12 m, route six turns of coax through the first supplied ferrite core to establish the main choke boundary.
• If the station entrance does not already have an effective choke, use the second supplied core there. If the entrance is already controlled, the second core may be placed directly after the first to increase the boundary impedance.

The choke does not make current disappear. It raises the impedance of the unwanted continuation path so the intended approximately 12 m section remains the principal exterior return. Confirm the result by measuring exterior-shield current at several positions and bands if the installation is unusual.

Tune in the Finished Position

Raise the antenna into its final geometry before making permanent length changes. Calibrate the analyser at the intended plane, sweep each complete amateur band and save the complex impedance—not only the minimum SWR.

1. Start on 80 m and bring the principal resonance toward approximately 3.6 MHz.
2. Check 40 m; the reference installation places its resonance near the upper end of that band.
3. Check 20 m and 10 m; the reference response places their resonances near the lower ends of those bands.
4. Expect 60 m to require an external tuner. Depending on the installation, 30 m and 15 m may also require one.
5. Recheck every band after any radiator, feed-line, choke, height or support change.

With the stated coax and a 7–8 m reference installation, the intended response is generally below about 2.5:1 SWR on the naturally covered bands and below about 3:1 on 80 m, where a tuner may still be useful. Those are setup targets, not universal guarantees: the installed geometry and surroundings decide the measured result.

Fold First, Cut Last

Fold excess wire back along the radiator and secure it temporarily. This keeps the adjustment reversible and lets you compare several positions. If the final installation requires cutting, remove only a small amount, raise the wire back to the same height and repeat the complete sweep after every change.

Do not tune by changing the station-side feed-line length until a prettier shack reading appears. That moves the measurement plane through a standing-wave pattern; it does not repair the load. Keep the deliberate approximately 12 m return section and choke boundary intact while adjusting the radiator.

Operate Within the Installation Boundary

• Never install, lower or adjust the antenna near energized overhead conductors. The wire, mast and longest handled object must remain unable to contact them.
• Do not touch the radiator, transformer, return section, choke or connectors while transmitting.
• Evaluate RF exposure for the power, duty cycle, frequency, antenna geometry and accessible areas required by local rules.
• Use local requirements and qualified advice for structural loading, bonding, earthing, surge protection and lightning protection. A feed-line choke is not a lightning-protection device.
• Lower and isolate the antenna before storms or maintenance when that can be done safely.

Engineering References

• ARRL: measuring installed common-mode current and chokes
• IEEE 145-2025: antenna and system terminology
• OSHA 1926.408: antenna and overhead-conductor safety principles

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