On Sat, 23 Oct 2010, Horst Stöcker wrote:
[...] So I can find just one conclusion: All of you who could reveive
Stefans transmissions must be living more or less on the countryside.
[...]
i live in the middle of Warsaw, yet i can receive Stefan's signal using a
miniwhip-like antenna. try these things:
- experiment with bias, my antenna likes to be fed with a higher voltage.
it would be better to tweak bias directly, but this is the only way to
change it, since the antenna in on the roof now.
- use at least lowpass filtering, and preferably bandpass. sound cards
really don't like to be fed signals above their nyquist frequency
- use a 12v gel cell for power and a laptop running on batteries for
testing, and see if there are considerable changes in the noise floor.
i've found that my bench power supply is ok, there is no difference if i
use it or the battery. but connecting the laptops power supply ruins rx
completly, this can be solved with an isolating transformer.
- try to use the goodies that Wolf put into spectrum lab, the noise
blanker and sample rate calibration make a difference. this is the first
time i've used the sample rate calibrator and it is really great.
- listen to the audio that reaches your soundcard input. if you hear a
radio station - use even more filtering :)
- look at your soundcard noise floor. for example i can eliminate some
noise by changing the max_cstate parameter in linux. you can probably do
similar things under other operating systems.
e-probes are great. i've tried running loops here, and the last time i
could receive SAQ was in 2006, since then the magnetic field noise floor
is just too high.
hope this helps,
Jacek / SQ5BPF
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