The provision of full coverage to the public can be a difficult task in terrestrial broadcasting. Sometimes, due to technical challenges and cost constraints, it may not be possible to deploy conventional signal distribution to transmitting stations. In these cases an on-channel repeater may be the only viable option. This paper describes a BBC digital on-channel repeater designed to extend the coverage of DAB services, believed to be the first device of this kind tested for broadcasting purposes in the UK. The unit receives a signal from a distant transmitter and re-broadcasts an amplified and slightly delayed version of it on the same frequency. In order to avoid instability caused by parasitic coupling between the receiving and transmitting antennas, stray transmitted signals are cancelled by an adaptive filter with a Least-Mean-Square estimator. The theory of operation is explained and hardware implementation is discussed. Results of a field trial are also presented.

This document was originally published in the Proceedings of the International Broadcasting Convention, September 2005.