Codan: HF Base Station Training

To compliment our standard radio training, we also offer High Frequency Base Station Installation training, below are examples of this course

Aim:

1. Enable participants to gain an understanding of the requirements and practical considerations for installing a base station HF system

Objectives:

1. 1. To understand the basics of
      • A fixed base station
      • The propagation direction of an antenna
      • Antenna take-off angles
      • Antenna mounting height and effects of frequency change
      • Installing an antenna and site selection
      • Antenna earthing

Antenna testing

A fixed base station consists of:

• Transceiver
• Antenna
• Power Supply

Topics covered include:

1. Installation of a fixed antenna
2. Installation of a transceiver
3. Testing the base station installations

Proper setup of the system ensures the quality of communication!

Important factors to consider when setting up an antenna:

1. Propagation direction
2. Distance of communication
3. Grounding
4. Antenna support structure
5. Antenna site selection
6. Installation of an antenna tuner

Antenna Propagation

• Depends on antenna type – horizontal or vertical antenna
• Horizontal antennas have complex radiation patterns, which depend on factors such as height and frequency. E.G, Diopole, broadband and long wire antenna
• Vertical antennas have omni-directional radiation patterns (equal radiation strength in all direction). Hence direction of antenna face is not important, e.g. vertical whip antenna

Distance of Communication

• Operating Frequency
• Take-off Angle
• Transceiver Power

Distance vs Frequency

• Shorter distances require lower frequencies
  • Larger antenna size
• Longer distances require higher frequencies
  • Smaller antenna size
• Size of antenna is inversely proportional to frequency

600-12004-118m x 38m1200-15005-186.5m x 31m2500-100007-285.5m x 26m

Approximate Path Length (km)	Frequency Range (MHz)	Antenna Mounting Dimension
0-300	2-6	13m x 58m
300-600	3-8	10m x 47m

What is take-off angle?

Elevation plot of the antenna radiation pattern

Distance vs Take-Off Angle

• Shorter distances require higher take-off angles
  • Antenna is installed lower
• Longer distances require low take-off angles
  • Antenna is installed higher
• Take-Off angle various by how high the antenna is mounted

Take-Off Angle (degrees)	Day Time (km)	Night Time (km)
0	3000	4500
10	1900	2900
25	1000	1600
40	550	1000
60	250	450
70	150	300
80	80	150

Height of a Fixed Antenna

Height of an antenna can be expressed in terms of physical height, H or wavelength

Controlling Take-Off Angle

For a fixed physical height, varying the operating frequency will effect the radiation pattern and hence vary the take-off angle.

For a fixed frequency, varying the physical height of an antenna will also effect the radiation pattern and hence vary the take-off angle.