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Showing posts from November 1, 2020

Audio sound card QRM VHF UHF

  This type is working very nice as alternative extra sound device for digital modes. it can work in DVD quality mode as recommended by the WSJT team But i noticed strong sparking type QRM from it at 144 and even stronger at 432 MHz  Tried to solve that with ferrite clamps and Aluminium foil without success.  At 144 i use the IC706 classic no external preamp  25m H2000  12eM2 at 22m ag.  Using no mast amplifier makes my receiving more sensitive for QRM  sources down near the receiver i am aware. But I keep in mind that the S/N ratio direct at the antenna clamps can only get worse from that point.  The trade off  is to amplify the antenna signal to a usable level adding lowest possible extra noise . At the same time keeping the dynamic range and selectivity high enough. The latest HEM Transistors make this easier then ever before. And the digital modes of WSJT instantly measure whether an extra pre-amp is really improving the SNR  or not. Earlier Type1 USB PCB causing less QRM it is rec


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