What effect will the transmission antenna have on the DRM signal?
The antennas used for FM broadcasting in VHF Band II are typically wide band structures capable of handling a number of FM signals at different frequencies. Such antennas should therefore be perfectly suitable for the transmission of DRM+, since a DRM+ signal is narrower in bandwidth (100 kHz) than an FM signal (c.200 kHz). Similarly, an HF broadcast antenna is usually a broadband structure and, since DRM30 signals at HF are no wider in bandwidth than analogue HF signals there should be no issues with antennas. At lower frequencies the situation is a little different as antennas for MF and particularly LF broadcasting tend to be much narrower in bandwidth. The effect of reduced antenna bandwidth on an analogue AM signal is to cause a loss of the higher audio frequencies due to a roll-off in the level of energy transmitted towards the outer edges of the upper and lower sidebands. Although this effect does reduce the quality of the received signal it is not disastrous and can often be co
