The invention relates to a method of controlling the operation of a voltage controlled oscillator (VCO) with respect to a SAW filter (6) within a broadcast data receiver (BDR) (104). Over time, it is found that during normal operation of the BDR (104), the SAW filter (6) is susceptible to frequency drift which can affect the operation of the BDR. In accordance with the invention, temperature readings are taken at various time intervals from within the BDR (104) to provide an indication of changes in temperature over time and, if the temperature does change in the BDR with time then the operating frequency of the VCO can be adjusted to a predefined frequency value which is appropriate for the temperature values measured. By adjusting the operating frequency of the VCO with changes in temperature, the drift of the SAW filter (6) can be compensated for, thereby ensuring the continued operation of the BDR (104) in the required manner.