I feel that there's an impact, and as for how significant it is, here's what AI says:
The relationship between the antenna and clothesline can be simplified as three-dimensional coordinates, including distance d, angle θ, and height difference h. The following is a quantitative analysis method based on empirical formulas and experimental data:
Harmonic frequency offset Δf: Δf = k₁ × (l/d) × sinθ,
Here, k₁ is a coefficient related to the antenna type and frequency (for 20-meter end-fed antennas, k₁ is approximately 100 kHz・m), l is the length of the clothesline, d is the shortest distance between the antenna and the clothesline, and θ is the angle between the clothesline and the antenna axis.
Change in SWR at Bobbi: ΔSWR = k₂ × (l/d²) × h, where k₂ is the empirical coefficient (approximately 0.5), and h is the maximum difference in height between the ends of the antenna and the clothesline.
Radiation pattern offset angle Δφ: Δφ = k₃ × (l/d) × cosθ, where k₃ is a coefficient related to the antenna's directivity (for typical end-fed antennas, k₃ is approximately 10°・m).
For example, if the length of the clothesline is l = 10 meters, the shortest distance between the antenna and the clothesline is d = 2 meters, the angle between them is θ = 45°, and the height difference is h = 1 meter, then:
The frequency offset Δf is equal to 100 ×(10/2)× sin(45°) ≈ 354 kHz.
The change in SWR at Bobbi is ΔSWR = 0.5 × (10 / 2²) × 1 = 1.25.
The angle of offset for the radiation pattern, Δφ = 10 ×(10/2)×cos(45°) ≈ 35.4°.
It is important to note that the above quantitative equations are based on simplified models and typical experimental data, and actual conditions may vary due to various factors.
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