Unit 3 — Assembly Procedures

TM-ANT-057 — Open Handout TM Chapter: Chapter 4 ELOs: Execute assembly in the correct sequence; achieve the physical dimensions specified Estimated time: 25 minutes

Step 1: Read the TM

Open TM-ANT-057. Read Chapter 4 — Assembly Procedures completely.

Then come back here.

Chapter 4 Content

CAUTION — RF EXPOSURE: Maintain minimum safe distance from all energized antenna elements during transmission. At QRP power levels (≤5 W) the MPE boundary is typically

  1. Install base mounting hardware and base insulator. Verify insulator breakdown voltage rating exceeds 2× operating RF voltage.
  2. Erect vertical element. For a guyed installation, use non-conductive guy ropes (Dacron); attach guys at top and 2/3 height.
  3. Install radial system. For buried radials: trench radials 2–4 in deep in lawn. For elevated radials: support at 1.5–2 m above ground, run outward from base.
  4. Bond all radials at the base via a radial bus ring (copper strap or ring terminal). Bond bus ring to coax braid at feedpoint.
  5. Connect center conductor of feed line to element base. Connect braid to radial bus ring. Weather-seal with self-amalgamating tape and UV jacket tape.
  6. Perform initial SWR sweep per Chapter 5 before first RF application.

Assembly Quality

Chapter 4 specifies 6 assembly steps.

Physical dimensions and assembly quality directly determine resonant frequency and feedpoint impedance: - Antenna length errors shift resonance: ~1% length error ≈ ~1% frequency shift at HF - Poor solder joints at the feedpoint create resistance that raises SWR and wastes power - Loose connections in a matching network change the impedance transformation ratio - Incorrect element spacing in a beam changes gain and front-to-back ratio - Coax shield continuity to the feedpoint determines how much common-mode current flows on the shield

If Chapter 4 specifies a pre-installation check (e.g., ohmmeter continuity or pre-resonance trim), do it. These checks catch fabrication errors before the antenna is in the air.

Self-Check Questions

SC3-1. How many assembly steps does Chapter 4 specify?

SC3-2. What is the specified length of the main radiating element? How was that length calculated?

SC3-3. Does Chapter 4 specify a feedpoint connection method? What is the correct solder or mechanical technique?

SC3-4. Does Chapter 4 require a pre-installation check? What does it verify?

SC3-5. If the assembled element is 2% shorter than specified, which direction will resonance shift? By approximately how much?

Answer Key

SC3-1. Count the numbered steps in Chapter 4.

SC3-2. See Chapter 4. The design length comes from the formula in Appendix A (typically 468/f or 234/f in feet, adjusted for wire diameter and proximity effects).

SC3-3. See Chapter 4. Good RF solder joints are smooth, shiny, and mechanically sound. Cold joints show up as dull, granular surfaces.

SC3-4. Scan Chapter 4 for verification steps before installation. Common pre-checks: DC continuity across element, coax shield-to-ground, open circuit across element center.

SC3-5. Shorter element = higher resonant frequency. At HF, the shift is approximately proportional: 2% shorter ≈ 2% higher frequency.

Checkpoint

Before proceeding: - [ ] You have read Chapter 4 completely - [ ] You can state the specified element length and its derivation - [ ] You have assembled the antenna per Chapter 4

→ Proceed to Unit 4