Merv's Brain Dump

Chapter 1 — Introduction and Scope

This manual covers structural requirements and installation procedures for four antenna support types: aluminum telescoping push-up mast (10–12 m), pneumatic air mast (7–9 m, rapid deployment), crank-up tower (10–30 m, non-crank-up portable variant), and guyed vertical mast. Wind load calculations follow EIA/TIA-222-H and ASCE 7-22.

Chapter 2 — Theory of Operation

2-1 Wind Load Calculation

The design wind pressure is:

q (Pa) = 0.613 × V²   (V in m/s)
q (psf) = 0.00256 × V²  (V in mph)

Design defaults:
  Operational: 50 mph (22.4 m/s) → q = 308 Pa
  Operational max: 70 mph (31.3 m/s) → q = 600 Pa
  Survival: 90 mph (40.2 m/s) → q = 990 Pa

The force on a cylindrical mast section (vertical member):

F (N) = q × C_d × A
  C_d = 1.0 (cylinder drag coefficient)
  A = projected area = diameter (m) × height (m)

2-2 Guy Wire Tension

For a guyed mast, the overturning moment M = F × h/2. Guy wire tension T = M / (r × cosθ), where r = guy radius and θ = angle from horizontal. For 45° guys: T = M / (r × 0.707). Use 3:1 safety factor on all guy wire ratings.

Chapter 3 — Equipment and Materials

Chapter 4 — Construction and Erection

4-1 Telescoping Mast Erection

1. Install the base plate on level ground. Anchor with 4×screw anchors or 4×250 kg sandbags in field operation.
2. Extend sections one at a time, starting from the bottom. Tighten each section clamp before extending the next.
3. Install guys at three levels: 1/3, 2/3, and top of full height. Guy radius must be ≥40% of height (rule of thumb); recommended 60%.
4. Tension all guys evenly. Mast vertical alignment: check with a plumb bob from the top. Adjust guys until mast is plumb to within 1°.

4-2 Pneumatic Mast

1. Extend collapsed mast horizontally. Connect air supply (bicycle pump, foot pump, or compressor) to the base Schrader valve.
2. Pump to 2.5–3.5 bar (36–51 psi). The sections extend sequentially from top to bottom. Full extension: approximately 60 pump strokes with a standard floor pump.
3. Once extended, set upright. Install base plate or drive the ground spike. Pneumatic masts are self-supporting to 9 m with no antenna wind load; add guys for wind exposure or antenna weight >2 kg.

Chapter 5 — Operating Procedures

1. Never erect a mast within fall distance of power lines. Required clearance: mast height + 3 m.
2. For portable operation, lower the antenna before moving the mast. Telescoping sections must be collapsed before transport; partially extended masts have the lowest collapse load capacity.
3. Inspect all guy wire attachment points before each use. Replace any guy wire showing kinks, broken strands, or corrosion at terminations.
4. In winds exceeding 50 mph: lower the antenna or lower the mast entirely if the design survival wind speed is less than the forecast wind.

Chapter 6 — Calibration

1. Measure actual mast height with a measuring tape or laser rangefinder. Record height at each clamp position for future reference.
2. Verify guy wire tension: each guy in a set of three should be tensioned equally. Use a wire tension gauge; target 10–15% of rated breaking strength for operational tension.
3. Plumb verification: with all guys tensioned, measure horizontal offset at the top with a plumb line. Must be <1% of mast height.

Chapter 7 — Verification and Acceptance

1. Mast plumb within 1% of height (e.g., <0.1 m offset for a 10 m mast).
2. All guy wires tensioned and attachment hardware secure (no loose turnbuckles, no shackle pins without cotter pins).
3. Wind load calculation completed and documented for the installed configuration (mast height, antenna size, design wind speed).
4. Log: date, mast type, height, antenna mounted, guy radius, design wind speed, tension measurements, operator.

Appendix A — Worked Wind Load Example

10 m aluminum mast, 50 mm OD, at 70 mph (31.3 m/s):

q = 0.613 × 31.3² = 0.613 × 979 = 600 Pa
A = 0.050 m × 10 m = 0.50 m²
F = 600 × 1.0 × 0.50 = 300 N (67 lbf) on the mast alone

Add 2-element Yagi (projected area ~0.5 m²) at top:
F_antenna = 600 × 1.2 × 0.50 = 360 N
Total F = 300 + 360 = 660 N (148 lbf)
Overturning moment M = 660 × 5 m = 3300 N·m (mast + antenna CG)

Guy wire tension (3 guys, 45° angle, 6 m radius):
T = 3300 / (6 × 0.707 × 2/3) = 3300 / 2.83 = 1166 N per guy
Use 1/4" Phillystran (rated 2200 N) with 3:1 safety factor.

Appendix B — Mast Tube Wall Thickness Reference