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How to improve GSM wireless signal?
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Mobile phone conversations in buildings are often difficult, if not impossible. This is due to the signal attenuation through walls, window panes, ceilings (underground). The problems occur in markets, tunnels, underground car parks, petrol stations, airport halls, hotels. A similar situation can be found in buildings located on the border range of base stations (recreational areas, mountains etc.).
The solution to this problem is application of a GSM repeater, being a two-way amplifier of wireless GSM signal, which significantly improves the quality of data transmission in such places, reducing noise and the number of lost connections.
How to choose suitable GSM repeater?
The following questions have to be answered to select optimum GSM repeater and accessories:
  • How much area is to be covered with the amplified GSM signal?
    • If up to 80m2 - the suitable device (outside cities) is the repeater Signal GSM-80 A6740,
    • If up to 300m2 - the suitable device is the repeater Signal GSM-300 A6760,
    • If above 300m2 - the suitable device is the repeater Signal GSM-300 A6760 with several A6800 indoor antennas.
  • How strong is the signal outside the building?
  • If the signal is very weak, the suitable outdoor GSM antenna is 20-element ATK 20/850-960 MHz A7028, directed towards the base station.
  • If the signal is weak or moderate, the suitable outdoor GSM antenna is 10-element ATK 20/850-960 MHz A7018, directed towards the base station.

Below - the specifications of the GSM repeaters:

Signal GSM-80Signal GSM-300
Frequency rangeUp Link: 890-915MHz, Down Link 935-960MHz,Up Link: 890-915MHz, Down Link 935-960MHz,
Output power
UL: 5dBm, DL: 5dBmUL: 15dBm, DL: 15dBm
GainUP: 35dB, DL: 45dBUP: 50dB, DL: 60dB
Coverage area
In-band ripple<3dB<3dB
Maximum group delay 1.5 µs1.5us
Out-of-band spurious emission< -40dBm < -40dBm
Impedance50Ω 50Ω
Antenna connectors
out. antenna: N-f, ind. antenna SMA socket,out. antenna: N-f,ind. antenna N-f
10V DC10V DC
Operating temperature range
-25°C to +55°C-25°C to +55°C
Operating relative humidity5%-95%5%-95%
Dimensions [mm]130x85x35293x148x35

Installation of GSM repeaters in buildings with the areas above 300m2.
SIGNAL GSM-300 A6760 is an ideal device for using in buildings with large areas, even over 300m2. The amplified GSM signal has to be distributed by GSM splitters and indoor GSM antennas.
In order to connect the indoor antennas with the GSM repeater one uses N-male to N-female cable (3m RF-5 E83281 or 5m RF-5 E83283). The total length of the repeater-antenna connections should not exceed 20m. Too long cables would excessively attenuate the output signal.
The output signal is distributed to several indoor GSM antennas (A6800) via GSM splitters. There are available splitters for connecting two (A6812) or three (A6813) antennas.
The diagrams below show example installations of SIGNAL GSM-300 repeater:
  • In a two-floor building,
  • In an assembly room of the area over 300m2.
GSM Antenna: ATK 20/850-960 MHz<br />(20-element, 10m cable, N-male)GSM Repeater Signal GSM-300Two-way GSM Splitter
Installation in a two-store building
GSM Antenna: ATK 20/850-960 MHz<br />(20-element, 10m cable, N-male)GSM Repeater Signal GSM-300Two-way GSM Splitter
Installation in a large hall
GSM Antenna: ATK 20/850-960 MHz<br />(20-element, 10m cable, N-male)GSM Repeater Signal GSM-1200Two-way GSM SplitterTwo-way GSM SplitterTwo-way GSM SplitterTwo-way GSM Splitter
Installation of a GSM repeater in a plant.
The installation has been done by DIPVISION company

To be able to hold smooth cellular phone conversation it is needed to obtain a stable signal at a level of minimum 4 signal bars, whereas inside the building the signal in certain places dropped to one bar.
Even outside the building the signal is only at a level of 3 bars.
GSM signal strength inside the building:
red - a practical loss of signal
orange - low signal
Diagram A - first floor
1 - office and residential space
2 - shop floor
Diagram B - second floor
Building structure:
  • Two floors
  • Bearing and partition walls made of hollow cinder blocks
  • Ceilings made of reinforced concrete
  • Roof covered with corrugated steel sheet
    The installation company used GSM repeater A6760 (for rooms up to 300 m2). The aim was to allow uninterrupted and clearer conversations in the office and residential premises.
    The Signal GSM-300 set includes the following elements:
    • Main unit (890-960 MHz),
    • 5m cable with N-male to N-male connectors,
    • Indoor antenna (on a mount, with N-f connector),
    • AC/DC adapter.
    It cooperates with outdoor antenna ATK 20 A7028 with integrated 10m cable terminated with N connector directly matching the antenna connector of the repeater.
    The place of installation of the Signal GSM-300 A6760 repeater has been residential house with office of 220 m2 area (15m x 15m) and adjacent shop floor of about 400 m2 (15m x 27m).
    GSM Repeater Signal GSM-300
    Installing Signal GSM-300 reapeater
    Installation steps:
    • Finding a place outside the building with a good GSM signal (900 MHz) - test installation with the ATK 20 A7028 antenna (direction).
    • Mounting the ATK 20 A7028 antenna on the UML-38L30 E8682C wall bracket.
    • Installation of the RF cable between the antenna and the repeater located in a suitable place inside the building (somewhere in the central part of the building/hall/room to be covered).
    • Mounting the GSM repeater close to an AC power outlet. It is recommended to protect electronic devices using safety multi-outlet extension cord with surge suppressor ACAR P7 P1316.
    • Deployment of indoor antenna/s ensuring even coverage of the whole area.
    • The indoor antenna/s should be at least 4 m away from the outdoor antenna - to eliminate possible interferences.
    • very stable signal at the level of 4 - 5 signal bars
    • stable voice connections
    • good coverage of the office/residential space as well as the shop floor
    Lower signal strength in certain areas is caused by the complicated design of the building (a narrow corridor, boiler room). The effect of the amplifier is well visible in the figure below:
    Green - very good signal
    Light green - good signal
    Yellow - sufficient signal
    Diagram C - first floor
    Diagram D - second floor
    The installation has been made by DIPVISION - antenna services from Krakow.
    A6740 - GSM-80 repeater for rooms up to 80 m2
    A6760 - GSM-300 repeater for rooms up to 300 m2
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