From: MarkusVester@aol.com
Message-ID: <154.11b53939.2a786cec@aol.com>
Date: Tue, 30 Jul 2002 18:27:56 EDT
Subject: Re: LF: Re: Power of Donebach 153kHz TX
To: rsgb_lf_group@blacksheep.org
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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