---
title: "Short note: Broadside vs endfire array"
subject: "Propagation and Antenna"
chapter: 2
key: "semester_6/propagation_and_antenna:broadside-endfire-short-note"
source: https://www.bctengineer.com/q/semester_6/propagation_and_antenna/broadside-endfire-short-note
site: BCT Engineering
---

# Short note: Broadside vs endfire array

Propagation and Antenna · Chapter 2: Antenna Parameters and Arrays

- Asked in: 2075 Baisakh, 4 marks
- Video: [Types of Antenna Array - Broadside array, End-fire array, collinear array](https://www.youtube.com/watch?v=95MfBLjrHsU) — Padmasri Naban
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/propagation_and_antenna/broadside-endfire-short-note
- Whole chapter: https://www.bctengineer.com/md/semester_6/propagation_and_antenna/chapter-2

## Question

Write a short note comparing broadside array and endfire array.

## Short answer

Both are uniform linear arrays differing only in progressive phase α. Broadside: α=0, beam at θ=90° normal to axis, bidirectional disc pattern, spacing λ/2, directivity ≈2L/λ. End-fire: α=-βd, beam along axis θ=0°, mostly unidirectional pencil beam, spacing λ/4, directivity ≈4L/λ (Hansen-Woodyard ≈7.2L/λ).

## Answer

A **broadside array** and an **end fire array** are both uniform linear arrays (equal amplitude, equal spacing *d*). They differ only in the progressive current phase α, which decides where the beam points. The array factor is AF = sin(nψ/2)/[n sin(ψ/2)], ψ = βd cosθ + α, with maximum where ψ = 0.

```text
Broadside (α = 0)          End fire (α = -βd)
      ↑ beam
  ● ● ● ● ●  ← axis       ● ● ● ● ● ⇒ beam
      ↓ beam               along the axis
```

| Feature | Broadside | End fire |
|---|---|---|
| Phase shift α | 0 (all in phase) | −βd |
| Beam direction | θ = 90°, normal to axis | θ = 0°, along axis |
| Pattern | Bidirectional; disc around axis | Mostly unidirectional |
| Usual spacing | λ/2 | λ/4 |
| FNBW | 2λ/(nd) | 2√(2λ/(nd)) |
| Directivity | ≈ 2L/λ | ≈ 4L/λ (Hansen-Woodyard ≈ 7.2L/λ) |
| Examples | Collinear, curtain arrays | Yagi-Uda, helical (axial mode) |

Key points:
- For the same length L = nd, the end fire beam is broader in angle terms but its directivity is about twice that of broadside.
- Broadside arrays are used for HF broadcasting and fixed links; end fire arrays for TV reception and point-to-point VHF/UHF links.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. According to the note, the two arrays differ only in
   A. the progressive current phase alpha
   B. the number of elements n
   C. the element spacing being exactly equal
   D. the polarization of the elements
   Answer: A. Both are uniform linear arrays; alpha decides where the beam points. (Key point: Basic difference)

2. For end fire (alpha = -beta d) the main beam points
   A. normal to the axis (theta = 90°)
   B. along the array axis (theta = 0°)
   C. at 45° to the axis
   D. in every direction equally
   Answer: B. Maximum occurs where psi = 0, which for alpha = -beta d is theta = 0°, along the axis. (Key point: Beam direction)

3. Which pattern pairing is correct?
   A. Broadside: unidirectional; end fire: bidirectional disc
   B. Both are omnidirectional
   C. Broadside: bidirectional disc; end fire: mostly unidirectional
   D. Both are strictly unidirectional
   Answer: C. Broadside radiates on both sides normal to the axis, end fire usually radiates one way along the axis. (Key point: Pattern type)

4. The Hansen-Woodyard condition for end fire raises directivity to about
   A. 2 L/lambda
   B. 4 L/lambda
   C. 14 L/lambda
   D. 7.2 L/lambda
   Answer: D. The extra phase delta = pi/n narrows the beam and raises D from 4L/lambda to about 7.2L/lambda. (Key point: Hansen-Woodyard)

## Related in Propagation and Antenna

- [Linear array; broadside vs end fire](https://www.bctengineer.com/question.md?key=semester_6%2Fpropagation_and_antenna%3Alinear-array-broadside-endfire) — Propagation and Antenna, chapter 2
- [Importance of arrays; end fire vs broadside](https://www.bctengineer.com/question.md?key=semester_6%2Fpropagation_and_antenna%3Aarray-importance-endfire-broadside) — Propagation and Antenna, chapter 2, asked 2×
- [Two-element array: broadside and end fire](https://www.bctengineer.com/question.md?key=semester_6%2Fpropagation_and_antenna%3Atwo-element-array-broadside-endfire) — Propagation and Antenna, chapter 2

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