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VLF: 2nd test grabber

To: [email protected]
Subject: VLF: 2nd test grabber
From: Stefan Schäfer <[email protected]>
Date: Wed, 19 May 2010 11:57:22 +0200
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VLF,

Just for the small group of VLF grabber interested OMs: To check the new location for my grabber i have set up a second grabber page that displays the signals of the test setup antenna with fiber optic cables. The page will be active just for some weeks. It is to compare differnt antenna (filter, input stage...) designs and earthing methods, also the QRM/QRN situation at this location. Further, one can compare the daily QRM/QRN minima and maxima there. It seems there is still a problem with IM in the first stage although i have added a band pass filter in the first stage (replaced the 100 Ohm resistor by a 3,3mH inductance (RDC=50 Ohm)). This suppresses the 50 Hz components and allows even 6 dB voltage gain for 9 kHz but it seems i need a low pass on the gate side, as DJ1ZB suggested. The levels of the BCD stns in the LF sector is extreme there, abt 20dB higher than at the current grabber(1) RX... Link of the 2nd temporarely grabber2: http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html

73, Stefan/DK7FC

PS: I have also added a wide band window, just as Markus has done it (still different scroll times but i will change that today).


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