A radio quiet zone is usually established around a radio astronomy station. Within such an area, motorised traffic is severely restricted or forbidden, and there may be several severe restrictions on the use of electronic equipment and on the existence of e.g. factories, buildings and construction works within the area: i.e. radio quiet means really quiet.
In addition, it is common practice for administrations to establish separation distances around radio astronomy stations for specific electronic equipment, such as mobile earth stations. These separation distances are usually larger than the extent of the generic radio quiet zone. These specific distances depend on the transmission characteristics of this equipment and on the frequency at which it operates.
In the different European countries, the situation for radio quiet zones is as follows:
| Country | Radio Astronomy Observatory | Separation distance from radio astronomy station | Regulatory Process |
| Finland | Metsähovi | About 1 km radius | The radio quiet zone has been established in consultation with the Finnish national regulatory authority |
| France | Nançay | 1 – 3 km | Radio quiet zone established by the French national protection zone law since December 2010. RQZ distance is one kilometre for electromagnetic compatibility with all devices and three kilometres for compatibility with emitters. Outside this RQZ, in the framework of the National Frequency Agency and the National Table of Frequency Regulation, the radio astronomy service may oppose the modification or installation of any transmitter which does not agree for the protection of a radio astronomy station. |
| NOEMA | 1 – 3 km | ||
| Ireland | Birr | Radio quiet zone not defined | |
| Italy | Medicina |
1.5 / 3 / 10 km radius |
The three protected zones have been established by the Medicina Municipality in the building regulatory plan respectively for civil buildings (1.5 km), buildings with technological equipments (3 km) and power lines >100 KV (10 km). Any new installation in these areas requires the approval of the Observatory |
| Noto |
No well-defined radio quiet zone or coordination area. |
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| Sardinia |
15 km |
Although no real radio quiet zone or coordination area is defined by regional regulation, since 2016 the Observatory can express opinion with a binding technical prescription, if a request for a new radio transmitter installation (or an upgrading of existing one) is submitted to the local municipalities office within an area of about 15 km around the telescope | |
| Spain | Yebes |
> 1 km |
Protected by a national law (https://www.boe.es/buscar/pdf/2014/BOE-A-2014-4950-consolidado.pdf) |
| IRAM-30M |
> 1 km |
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| Robledo de Chavela |
> 1 km |
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| Cebreros |
> 1 km |
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| Sweden | Onsala |
Radio quiet zone not defined |
Act on Protection of Research Sensitive to Disturbance |
| Ukraine | All observatories |
Radio quiet zone not defined |
Note: The separation distance depends on the characteristics of the radio astronomy station (whether it is a single dish instrument, an interferometer or participating in Very Long Baseline Interferometry), the frequencies used and the research priorities (spectral line or continuum emission).