Dear LF,
Since about 2 weeks i am running a 137 kHz grabber page that covers QRSS-30/60/120/240
(600 will be added).
Due to some noise problems (like on the LF grabber as well) i made a
secret out of this webpage. Sometimes it seems to work very good, some
minutes later i have strong QRM... Last sunday morning i captured
"XGJ" so it cannot be too bad. Today i applied the SpecLab internal
filter (band pass, bw abt 2 kHz, 400 Hz slopes, removing the strong
carrier of DCF39 but not its bursts, to get an effective blanking and
limiting) which made a great difference at once! But the noise that
suddenly appears is a broad band noise. I am sure to solve these
problems but not before i go to France tomorrow :-)
Since i want to try some DX on 137 i want to publish the website today:
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_LF_DX_Grabber.html
Maybe this can help giving some orientation for others, by finding my
weak trace at least in Heidelberg ;-) The PC has shut down 2 times and
i don't know why. I have increased the swap file and reduced to 6
SpecLab instances and hope this helps.
The grabber has a omnidirectional antenna and wants to cover from very
low noise to high noise (since it runs remote) so i have to choose
either the AGC or a wide color scale (currently about 20 dB) so it will
not show screenshot like others can create, when sitting in front of
the PC and adjusting to maximum contrast and optimum brightness for
each signal received station.
The grabber will run 24/7, even during holidays and thunderstorms and
summer time :-)
Also it wants to allow the very weak LF stations to "write" something
on the screen by using a very slow mode (like DFCW-240) and a STABLE
carrier!
The grabbers soundcard drift is compensated by using SpecLab and a GPS
module with a 10 kHz reference output. Currently, the IF has an
acurracy of about +-30 mHz (temp drift of xtal). This xtal will be
locked to GPS in some weeks. After that, the 600 window will appear.
Ok, wish you fun. I would be glad to receive some traces there but
don't be disappointed if the signal is lost in the QRM.
73, Stefan/DK7FC
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