GSM Off-Air Tester for Longer Distances
Using the typical test setup, the mobile is connected to the 4208 by two antennas. When testing the mobile phones we suggest using Willtek´s antennas recommended for the desired frequency band. For better isolation between the receive and transmit paths, it’s helpful to arrange the two antennas at an angle of 90 degrees.
The maximum distance between the 4208 and the mobile phone depends on local conditions. In open space up to 100 metres is achievable; this is why users must take precautions against interference with public cellular networks. Appropriate shielding arrangements can help to attenuate the signal outside the building so that the signal level does not violate regulations set by local authorities.
Testing hands-free kits and their connections to microphones and loudspeakers is a key application for the 4208. Radiating cables are mounted above the assembly lines, where the cars with hands-free kits or other extra equipment are located for measurement. The radiating cables above the assembly line are sometimes more than 50 metres long. This allows tests to be done almost independent of the car position on the production line. By introducing separate connectors for the receive and transmit paths, an external amplifier can be connected to the 4208 to further increase the operating range. The user must, however, take measures to conform to national radiation limits and to avoid interference with local cellular networks.
In order to avoid other mobile phones in the vicinity from locking on the 4208 signal, the user can restrict the allowable phone numbers to a definable range so that other phones will be rejected. The 4208 can perform a power measurement while the phone is registering with it. This can be used to automatically test the antenna installation without manual intervention because the user does not need to set up a call for this check.
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