INTERNATIONAL TELECOMMUNICATION UNION
RADIOCOMMUNICATION
STUDY GROUPS
Document: 3J/UK6-E
24 May 2001
Original: English
United Kingdom
INDOOR RECEPTION MEASUREMENTS OF UHF TELEVISION SIGNALS
1. Introduction
A campaign of measurements was initiated in 2000 with the specific purpose of measuring the
parameters needed for planning indoor portable reception of digital terrestrial television
services. The parameters measured were building entry loss, height gain, field strength
difference between floors, and field strength variations within the buildings. The
measurements were analysed to derive the median values and the standard deviations of these
parameters.
2. Measuring Equipment
In order to make field strength measurements, an accurately calibrated receiving antenna was
needed. The antenna used was a BBC R&D designed log-periodic type with a gain of 5 dB.
This antenna was mounted on a boom to allow it to be hand held without the presence of the
operator significantly affecting the received signal level. The measurements were made using
a portable measuring receiver connected to the antenna. Since the gain of this antenna is
known, these signal strength measurements could easily be used to calculate field strength
values.
Measurements of both digital and analogue television signals were made. These signals were
transmitted from UK television transmitting stations and were the transmissions intended to
provide television services to the houses concerned. Since the locations of the houses covered
a large geographical area, the measurement campaign included measurements from several
transmitting stations using channels throughout the UHF broadcasting bands. From the
measurements the building entry loss and other parameters were calculated for the whole
UHF band and for the two broadcast sub-bands (Bands IV and V) separately. Band IV is from
470 MHz to 582 MHz and Band V is from 614 MHz to 854 MHz.
The houses measured were typical of UK building construction with brick walls, wooden
floors and tiled roofs. They were located in suburban areas.
3. Measurement of Planning Parameters
The measurement of the relevant parameters will now be discussed
3.1 Building entry Loss
Building entry loss was defined as the difference between the mean field strength inside a
building at a given height above ground level and the mean field strength outside at the same
height.
For the purpose of this study, the outside values were measured using the hand-held receiving
antenna. The antenna was held at about five outdoor locations on the side of the building
nearest to the transmitter, at a height of about 1.5 metres above ground level. The outside
value was calculated as the mean value of these measurements.
The inside values were measured using the same hand-held antenna. Two ground-floor rooms
were measured for each building. The two rooms were chosen to be on opposite sides of the
building so that one was on the side nearest to the transmitter and one was on the side furthest
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from the transmitter. For each room, a number of measurement points were chosen
throughout the room. A measurement was made at each of these points and the average was
calculated for each room. An average was also calculated for the whole ground floor from the
measurements for both rooms. The number of measurement points for a typical room was
about ten.
It was not generally possible to locate the measuring antenna at a suitable height outside of
the buildings to allow building entry loss to be determined for upstairs rooms. The derived
values are, therefore, confined to ground floor rooms.
3.2 Height gain
The height gain was measured outside the houses and is the difference in field strength
between the standard antenna height of 10 metres, assumed for fixed reception, and the height
of 1.5 metres assumed for portable reception.
For this study, the 1.5 metre measurement was the average of five outdoor measurements
already used in the building entry loss determination. The 10-metre measurement was made
using the professional Log-Periodic antenna mounted on the 10-metre mast of a BBC R&D
survey vehicle.
3.3 Difference in signal levels between floors
For planning it may be assumed that less field strength is required at 10 metres to provide
portable coverage in first floor rooms compared with that required for ground floor rooms.
This reduction in required field strength for first floor rooms can be measured as the
difference in field strength between the two floors.
To measure this figure, field strength measurements were also made in two rooms on the first
floor of the houses. As before, these were chosen to be on opposite sides of the building. The
difference in the average field strength for the two floors was calculated.
3.4 Standard deviation within rooms
The measurements within rooms were analysed to determine the standard deviation of the
variation of field strength within a room.
3.5 Standard deviation on a single floor
The measurements on single floors were analysed to determine the standard deviation of the
variation of field strength on a single floor.
4. Results
4.1 Building Entry Loss
Table 1 gives the median of the ground floor building entry loss values for all of the buildings
measured. The table also gives the standard deviation of these values. The median value is
around 8 dB. The value for Band V seems to be slightly higher than for Band IV. The
standard deviation was approximately 5 dB.
Table 2 and Table 3 give the median and standard deviation of the building entry loss values
for single ground floor rooms on different sides of the building. There is a clear difference
between rooms depending on whether they are on the side nearest or furthest from the
transmitter. Rooms on the side of the building furthest from the transmitter gave a median
building entry loss about 5 dB greater than those on the opposite side.
All UHF
Band IV
Band V
Median
8.1
7.8
8.1
Table 1. Building entry loss (ground floor)
Standard Deviation
4.7
4.6
5.1
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All UHF
Band IV
Band V
Median
10.3
10.4
9.7
Standard Deviation
5.0
5.8
3.5
Table 2. Building entry loss (ground floor rooms furthest from transmitter)
All UHF
Band IV
Band V
Median
5.4
5.4
5.4
Standard Deviation
5.2
4.9
5.8
Table 3. Building entry loss (ground floor rooms nearest to transmitter)
4.2 Height Gain
Table 4 shows the median values of height gain measured outside the houses. Note that the
houses were in suburban locations. The median value for all UHF measurements was 13.5 dB.
It is noted that the value for Band V is lower than for Band IV. Diffraction theory would
suggest the opposite. This result is probably due to the nature of the local clutter at the
locations where the various transmission channels were available.
All UHF
Band IV
Band V
Median
13.5
14.7
12.9
Standard Deviation
7.9
7.6
7.6
Table 4. Height gain
4.3 Difference in signal levels between floors
Table 5 shows the difference between the mean ground floor field strength and the mean first
floor field strength. The median value for all UHF measurements was approximately 5.5 dB.
As before, the difference between Bands IV and V is not thought to be significant.
All UHF
Band IV
Band V
Median
5.4
4.3
6.1
Standard Deviation
2.6
2.4
2.7
Table 5. Field strength difference between ground and first floor
4.4 Standard Deviation within rooms
Table 6 gives the average standard deviation of the variation of field strength within all of the
rooms measured. Table 7 to Table 10 give values for all four categories of room measured. It
can be seen that, generally, the standard deviation within a room is around 3 dB. Band V
tended to produce slightly lower values than Band IV. Also, rooms on the side of the building
furthest from the transmitter tended to give slightly lower values than those on the side
nearest. This may reflect the absence of a strong direct signal through the window. Instead,
the signals may reach the receiver via a number of paths – reflected from objects outside,
through the building etc.
All UHF
Band IV
Band V
Average St Dev
3.0
3.1
2.8
Table 6. Standard deviation within rooms (all rooms)
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All UHF
Band IV
Band V
Average St Dev
3.1
3.0
3.2
Table 7. Standard deviation within rooms (ground floor rooms nearest to transmitter)
All UHF
Band IV
Band V
Average St Dev
2.6
2.7
2.4
Table 8. Standard deviation within rooms (ground floor rooms furthest from
transmitter)
All UHF
Band IV
Band V
Average St Dev
3.1
3.2
3.1
Table 9. Standard deviation within rooms (first floor rooms nearest to transmitter)
All UHF
Band IV
Band V
Average St Dev
2.8
3.0
2.5
Table 10. Standard deviation within rooms (first floor rooms furthest from transmitter)
4.5 Standard Deviation within a floor
Table 11 and Table 12 give the average standard deviation of the variation of field strength
measured within a single floor of the buildings. It can be seen that the standard deviations are
somewhat larger than for a single room. This would be expected since the values will include
the difference in building entry loss between the two sides of the building.
UHF
Band IV
Band V
Average St Dev
3.8
3.9
3.7
Table 11. Standard deviation for ground floor
UHF
Band IV
Band V
Average St Dev
4.3
4.5
4.1
Table 12. Standard deviation for first floor
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5. Conclusions
A number of conclusions can be drawn from this work.

The median building entry loss at UHF was found to be 8.1 dB.

The standard deviation of the variation of building entry loss was 4.7 dB.

There is evidence of larger values of building entry loss in rooms facing away from the
transmitter. The median value for such rooms was 10.3 dB, whereas the corresponding
value for rooms on the side of the building nearest to the transmitter was 5.4 dB; a
difference of about 5 dB.

A median value of 13.5 dB was measured for the outdoors height gain between 1.5 and 10
metres. The locations of the measurements were suburban.

The median value of the difference in field strength between ground floor and first floor
rooms was found to be 5.4 dB.

The standard deviation of the variation of field strength within rooms was about 3 dB.

The standard deviation of the variation of field strength measured for a floor of a house
was about 4 dB.
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