For amateur base station installations it is recommended that the clearance in front of the antenna array is calculated relative to the EIRP (Effective Isotropic Radiated Power). The clearance height below the antenna array can be determined in most cases from the RF power at the antenna input terminals.
Different exposure limits have been recommended for different frequencies, a relative table shows a guideline for installation considerations.
Below 30 MHz, the recommended limits are specified in terms of V/m or A/m fields as they are likely to fall within the
Exposure distance assumes that the predominant radiation pattern is forward and that radiation downward is at unity gain (side lobe suppression is equal to main lobe gain). This is true of almost every gain antenna today. Exposed persons are assumed to be beneath the antenna array and have a typical height of 1.8 m.
The figures assume the
For the bands 10 MHz and higher the following power density limits have been recommended:
1 | Watts | 2.1 m |
10 | Watts | 2.8 m |
25 | Watts | 3.4 m |
100 Watts | 5 m | |
1000 Watts | 12 m |
100 Watts | 2 m | |
1000 | Watts | 6.5 m |
10,000 | Watts | 20 m |
100,000 | Watts | 65 m |
In all cases any possible risk depends on the transmitter being activated for long periods. (actual recommendation limits are specified as an average during 6 minutes) Normally the transmitter is not active for long periods of time. Some radio licenses will require that a timer circuit automatically cuts the transmitter after
Similarly some types of emission, i.e., SSB, CW, AM etc. have a lower ‘average’ output power and the assessed risk is even lower.
Versions of the
This warning symbol indicates that this equipment operates in
| Country | Codes |
| Country | Codes |
1 | Austria | AT | 18 | Liechtenstein | LI |
2 | Belgium | BE | 19 | Lithuania | LT |
3 | Bulgaria | BG | 20 | Luxembourg | LU |
4 | Croatia | HR | 21 | Malta | MT |
5 | Czech Republic | CZ | 22 | Netherlands | NL |
6 | Cyprus | CY | 23 | Norway | NO |
7 | Denmark | DK | 24 | Poland | PL |
8 | Estonia | EE | 25 | Portugal | PT |
9 | Finland | FI | 26 | Romania | RO |
10 | France | FR | 27 | Slovakia | SK |
11 | Germany | DE | 28 | Slovenia | SI |
12 | Greece | GR | 29 | Spain | ES |
13 | Hungary | HU | 30 | Sweden | SE |
14 | Iceland | IS | 31 | Switzerland | CH |
15 | Ireland | IE | 32 | Turkey | TR |
16 | Italy | IT | 33 | United Kingdom | GB |
17 | Latvia | LV |
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