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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