Hi Dick and the group,
I am pretty sure Donebach uses some form of controlled carrier modulation,
apart from the phase modulation mentioned by Walter.<<
Yes, DLF does use "dynamic AM" modulation, with up to 3dB carrier reduction
at low audio levels. The variable carrier level is generated along with the
audio in the control circuit of the Telefunken PANTEL switched-mode modulator
stage, operating at 54kHz.
During normal daytime operation, both transmitters are combined, and the
carrier power varies from about 250 to 500 kW. The two-mast antenna system
then has a directional minimum of nominally minus 3dB /monopole towards
Romania (SW, abt. 110°), and a gain of about 2dB to the NW. So with only one
TX operational (125...250kW), one would expect 200...400kW EMRP towards the
Netherlands. - As Walter has said, at night regularly a single TX is used,
and the antenna system is fed differently to provide a deeper null with -10dB
vs. +2dB directivities.
73 de Markus, DF6NM
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