OMVC releases new tools to improve VHF reception

The mobile video group's new “Predictive Model” can predict signal coverage in automobiles with an antenna mounted on the vehicle, in a handheld unit operating outdoors and with a handheld unit operating indoors.
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On Tuesday, Jan. 1, the Open Mobile Video Coalition (OMVC), the main advocacy group for the development of mobile digital television since 2007, was officially integrated into the NAB. The group also released new tools to aid television engineers improve the reception of mobile signals on VHF channels 7 through 13.

The mobile group released a new “Predictive Model” report that is intended to predict signal coverage in automobiles with an antenna mounted on the vehicle, in a handheld unit operating outdoors and with a handheld unit operating indoors.

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Broadcast engineers can use this new model to predict future coverage of existing or future transmission facilities. The new report complements an earlier UHF Predictive Model that detailed reception characteristics for broadcasters operating on channels 14 and higher.

“Mobile TV is designed to be transmitted alongside the same digital TV broadcasts that bring local news, weather, traffic, sports and favorite programs to viewers in high-definition,” said Anne Schelle, executive director of the Open Mobile Video Coalition. “But the signal qualities of Mobile TV are quite different than HDTV transmissions, because reception antennae in Mobile TV receivers are usually lower to the ground and always on the move. We want broadcasters transmitting on VHF channels 7 through 13 to be aware of what transmission methods best serve a viewer who is walking, or a passenger who is watching while riding in a car.

“While there are different models used to predict broadcast signal coverage, we’ve opted for a ‘semi-empirical’ method that uses a blend of actual field reception data and theory. With information about the local terrain, antenna height, frequency, and polarization as well as details about the receiver and atmospheric conditions, we can predict signal strength for mobile broadcasts with this model,” Schelle said.

The results, she said, are local maps that show where Mobile DTV reception can be expected to be robust. Subsequent field-testing with automobiles showed the predictive model to accurately correlate to actual conditions.

The new 20-page VHF Propagation Model report is available online.