How a mast compares
with everything else.

The rest of this site answers one question: what does the mobile network put into the air at a given point? For most people that is not the only radio-frequency source in their day, and for many people it is not the largest one. This page puts the mast in context.

One fact decides most of it before any number is quoted. Field strength falls with the square of distance, so ten times further away is a hundred times weaker. A mast is permitted hundreds to thousands of watts and stands a hundred metres away or more; a handset is a fraction of a watt centimetres from your head. Those two facts pull in opposite directions, and the arithmetic below is what settles it.

Uplink and downlink — the two directions of "normal phone connectivity"

A mobile link runs both ways, and the two directions are not the same exposure at all:

• Downlink — the mast transmits to your phone. This is what this map models. It runs continuously, whether or not anyone is using a phone, and it is the exposure a person who does not own a mobile phone still receives.
• Uplink — your phone transmits back to the mast. It runs only while the phone is actually sending, it is a small fraction of a mast's permitted power, and it is radiated from an antenna centimetres from your hand or your ear. For that reason it produces the highest exposure at the body of anything on this page.

The network sets the handset's uplink power and lowers it as reception improves; that is what the power-control signalling between mast and phone is for, and it is why battery life improves where the signal is strong. The practical consequence is worth stating plainly: the exposure from your own handset is the part of it that responds to what you do. A basement, a deep valley, a train carriage with metallised windows or a thick-walled building all force the phone to transmit harder, and improving reception — a call over Wi-Fi, a window, a different room, a wired connection — reduces it.

Because the handset radiates into your body at a distance of centimetres, its exposure is not expressed as power density but as SAR (specific absorption rate): watts absorbed per kilogram of tissue, limited internationally to 2 W/kg averaged over 10 g for the head and trunk. A mast a hundred metres away is a plane wave, and power density is the right measure for it — which is why this page quotes both and never converts one into the other.

What each source may transmit

These are regulatory maxima and typical values — what a device is allowed to do, not what it is doing at this moment. A device at its maximum has to be doing something: holding a call, streaming, or reaching across a house.

The mast row is the one the register states precisely. Every installation in it is filed in one of four power classes, and the class is a permitted maximum rather than what the site transmits: of the 22,482 register rows behind this map, 4,433 rows are ≤6 W, 3,249 are ≤500 W, 13,070 are ≤5,000 W and 1,730 are above 5,000 W. So a single mast is permitted four to eight orders of magnitude more power than a router — and it also stands a hundred to several thousand metres away, which is the whole of the comparison.

The same arithmetic at a distance

Field strength and power density are locked together by the impedance of free space, and a transmitter's power spread evenly over a sphere of radius d gives a power density of P / (4πd²). That is the same intermediate quantity this map's model starts from, so the table below is the map's own yardstick applied to everything on the page.

Two dashes and one column need explaining. A dash means the distance is not a meaningful one for that source: you cannot stand a metre from a mast's antenna, which is metres above you, and at those ranges the plane-wave formula stops describing a nearby device as well. The column of dashes is the same point from the other side — a mast's numbers at 100 m and 1 km assume a clear line to the beam's axis, and the map's model does better than that, applying the panel's vertical pattern so ground level below the beam reads far lower. That vertical pattern is also why the map's contours stop closer in than this table suggests, and it is the reason the strongest modelled ground-level ring around a mast sits about 85 m out rather than at its foot.

As a check on the arithmetic rather than on the physics: the highest outdoor value the federal measurement programme has ever recorded anywhere in Switzerland is 0.48 V/m, which is about 610 µW/m². A Wi-Fi router at its permitted 100 mW produces that at roughly 3.6 m. A typical Swiss village centre as measured — 0.09 V/m, about 22 µW/m² — is what the same router produces at roughly 19 m. Neither figure is an argument that routers are dangerous; both are a scale against which the federal measurements can be read.

The one number that makes them comparable

Everything above reduces to a single question: at what distance does each source produce the level this map draws its contours at, the shipped 200 µW/m² default? In the same free-space arithmetic, before any beam pattern is applied:

• a Bluetooth class-2 device — a keyboard, earbuds, a watch — about 1 m;
• a Wi-Fi router at its permitted 100 mW — about 6 m;
• a 5 GHz access point at 200 mW — about 9 m;
• a DECT cordless phone at 250 mW — about 10 m;
• a mast in the very-low class, up to 6 W — about 49 m;
• a mast in the low class, up to 500 W — about 450 m;
• a mast in the medium class, up to 5,000 W — about 1.4 km.

Both halves of that list carry a qualification, and the comparisons only work with them in place. The masts' distances are quoted before the vertical pattern, which the map applies; ground level is well below the beam's axis, so a fan on the map is rarely as long as the free-space distance. And "at its permitted maximum" is a real qualification for the small devices: a router transmits at 100 mW when it is holding a long range on a busy channel, and far less, in short bursts, when it is idle two metres from the device it serves.

What measurement finds next to them

The figures below are published measurements, not model output, converted to power density using the same relation the rest of the site uses.

The shape of that table is the answer to the question this page exists for. The largest measured numbers in an ordinary day come from devices within a metre of the person, not from masts — and the numbers next to masts are the smallest in the table. That is not a claim that a mast is harmless, and it is not a claim that a router is the thing to worry about either. It is simply where the exposure sits.

The World Health Organization reaches the same conclusion from the measurement side: in publicly accessible places, including schools and hospitals, outdoor exposure from base stations normally comes out thousands of times below the international reference levels, and is lower than or comparable to exposure from radio and television broadcast — which the body absorbs up to five times more of at the same field level, because those frequencies are lower and a person's height makes them an efficient receiving antenna.

Two limits put the table above in proportion. The international reference level for the general public across these bands is 61 V/m at 2 GHz and above, and about 41 V/m at 900 MHz — between fifty and a hundred times the highest measured value in this country. The Swiss installation limit is far stricter, 4–6 V/m at sensitive locations, and the smart-meter and router readings above do sit within a factor of a few of it: that is not a coincidence, it is why the Swiss approach is often described as precautionary, and it is also why a reading taken at 30 cm from a device says very little about the same device at two metres.

Bluetooth, Wi-Fi 2.4 GHz, Wi-Fi 5 GHz and mobile data, side by side

• Bluetooth is the least powerful of the group by one to two orders of magnitude — 2.5 mW on the class most keyboards, earbuds and watches use, against 100 mW for Wi-Fi — and it sends in short bursts rather than continuously. At a metre, while it is transmitting, it produces about the level this map draws as its threshold; averaged over a day it is a small fraction of that.
• Wi-Fi at 2.4 GHz shares its band with Bluetooth, microwave ovens and every neighbour's router, which is why a router often sits at its permitted 100 mW to hold range. It passes through walls better than the higher band.
• Wi-Fi at 5 GHz is allowed two to ten times more power, and is absorbed much more strongly by walls and by water — people included. In the same room at the same distance it reads roughly twice the 2.4 GHz level; through a wall it reads considerably less. Its shorter range follows from the same property.
• Mobile data — the 4G and 5G uplink — is bracketed by the network between roughly 0.12 and 0.2 W averaged, and the antenna is against your hand or your head rather than across a room. Its most useful property is that it falls as reception improves, so it is the one item here that a change of position reliably reduces.
• 2G voice, still the layer the railway installations in the register are filed under, is where handset peak powers are highest: up to 2 W per pulse at 900 MHz, though time-averaging over the frame brings that to 0.25 W.

None of these can be ranked by a single number, and the reason is worth keeping in mind. A mast, a router and a cordless base station radiate into the air at a distance, so power density describes them. A handset and a smart meter in your hand radiate into you, so SAR does. Converting between the two is not a unit change but a category error, which is why the two measures appear side by side on this page and are never added together.

References

• World Health Organization — base stations and wireless technologies →
• German Federal Office for Radiation Protection (BfS) — wireless applications in everyday life: Bluetooth, Wi-Fi, DECT, Zigbee, LoRaWAN and UWB power limits →
• German Federal Office for Radiation Protection (BfS) — mobile terminals: handset transmit power and SAR →
• Irish Environmental Protection Agency — Wi-Fi, smart meters and your health, with measured levels →
• ICNIRP — radiofrequency EMF guidelines, 100 kHz to 300 GHz →
• ARPANSA (Australia) — radiofrequency radiation, and how exposure falls with distance →

Measured Swiss values are the federal measurement programme's, as set out on Radiation levels · external links are references, not affiliations, and carry rel="nofollow"