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7/8 vs 5/8 wave Antennas

Both the 7/8 wave and the 5/8 wave antennas are commonly used in radio communications, particularly in HF, VHF and UHF frequencies. Each type of antenna has its own set of advantages and characteristics. Let's compare the two:

1. **Radiation Pattern**:

- **5/8 wave**: It typically has a flatter radiation pattern compared to a quarter-wave or half-wave antenna. This flatter pattern gives better ground coverage and is often chosen for mobile communications where maximum ground coverage is desired.

- **7/8 wave**: A 7/8 wave antenna would further depress the radiation angle. In practice, 7/8 wave antennas are less common than 5/8 wave antennas for mobile use due to their length and difficulty in implementation.

2. **Gain**:

- **5/8 wave**: A 5/8 wave antenna usually has more gain (around 3 dB) over a quarter-wave antenna due to its radiation pattern being more focused towards the horizon.

- **7/8 wave**: The gain would be even slightly higher than the 5/8 wave, but the difference might not be significant enough to justify the additional height and complexity.

3. **Height**:

- **5/8 wave**: It's taller than a quarter-wave or half-wave antenna, but is still manageable for many mobile and fixed applications.

- **7/8 wave**: Given its size, it becomes less practical for mobile applications but might still be used in certain fixed station setups.

4. **Impedance Matching**:

- **5/8 wave**: This antenna doesn't naturally resonate at 50 ohms, so it often requires an impedance matching network or a coil at its base.

- **7/8 wave**: Similarly, a 7/8 wave antenna would require impedance matching to work efficiently with typical 50-ohm radio systems.

5. **Installation**:

- **5/8 wave**: While longer than some other common antennas, it's still reasonably manageable for many installations.

- **7/8 wave**: Due to its longer length, the 7/8 wave antenna becomes less practical for mobile installations and can be more challenging to install and stabilize.

In summary, while the 5/8 wave antenna is a popular choice for mobile radio communications due to its improved ground coverage, the 7/8 wave antenna is less common due to its increased length and installation challenges. However, in situations where maximum gain and a depressed radiation angle are desired, and installation challenges can be managed, the 7/8 wave might be considered.

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