Hi Paul, What is the ideal pulse length, amplitude and shape for vlfrx tools? Can you show a reference graph? 73, Stefan Am 17.06.2017 19:59, schrieb Paul Nicholson: Then there's a high pass getting
I don't know if there's an optimum length but I tend to run at 2mS pulse width. Probably anything in the range 1mS to 10mS would do about as well. I have found very short pulses, eg the 10uS pulse f
All the vt programs write float8 to their output stream (buffer, pipe, file, network) regardless of the input format. The only exception is vtwrite which writes to its signal database in the format o
Hi Paul, I spent some more time on the 2 (3) channel portable VLF recorder using the Raspi, the octo-soundcard and vlfrx tools. Meanwhile vttime is running. The GPS pulse is shortened to 2 ms (by sof
I had to call the vlfrx tools from /usr/local/bin into that script, otherwise nothing happened. at the begining of the script insert: export PATH=$PATH:/usr/local/bin you won't have to use the full p
Yes, vttime will be using most of a core, @raw is 8 channels and it's having to do a high quality resampling on them all. If you only want 3 channels, use @raw:1,2,3 for input to vttime. vtresample w
Hi Paul, Thanks for the quick reply. Thanks for the hint regarding @raw:1,2,3. That will further help to reduce the CPU load. So you seem to confirm that the CPU usage is normal for what i have done.
Hi Paul, Am 06.07.2017 20:13, schrieb Paul Nicholson: Looks bad. Run the signal through vtstat -i to see if channel one is clipping at all. vtread ... | vtstat -i Maybe both channels are close to hit
That looks fine, no clipping. Curious. Need to find out what those glitches on the SL spectrogram actually are. You've eliminated a lot of possibilities with the tests so far. Probably not, until we
Hi Paul, Meanwhile i did more tests: Used two audio isolation transformers to DC-separate the inputs: No difference. Am 07.07.2017 20:02, schrieb Paul Nicholson: Can you send or put on the web a shor
...another test on all 6 inputs. I generated 3 wav files of each channel pair and played them in SpecLab. BTW the signal generator is my DDS VFO that i used in the first VLF kite experiments. http://
Interesting. The first thing I notice is some curious effects on the background noise, on ch1 only, eg vtcat -S49 -E2 170708-095003 | vtrsgram -ox -g200 -- -:1 (ctrl-C in the shell to quit) or with v
So far, unable to reproduce the effect here with much the same setup. sig gen -> octo -> vtcard | vtresample -r24000 -- -,i2 | vtwrite What signal voltage does your DDS put into the Octo? What input
Hi Paul, thanks for the analysis and the tutorial :-) Am 09.07.2017 07:46, schrieb Paul Nicholson: What signal voltage does your DDS put into the Octo? It was at 10 mV +- 0.5 mV. What input gain is a
Hello Markus, Am 09.07.2017 11:34, schrieb Markus Vester: First I thought it might be flicker noise on the ADC reference voltage but why should it affect only three of six channels? Right. With USB
Let's try an experiment. Capture a short sample 6 channels 96k/sec int2 format, directly into a file. No input, all inputs open circuit. Max alsamixer gain. Hopefully capture where at least one chann
Here it is: www.iup.uni-heidelberg.de/schaefer_vlf/VLF/test.vt 73, Stefan Am 09.07.2017 19:33, schrieb Paul Nicholson: Let's try an experiment. Capture a short sample 6 channels 96k/sec int2 format,
Hi Paul, Markus, OK, here are the results from additional tests. I took a record from CH1 and CH2 again, this time corrected by vttime which is getting PPS from CH3. http://www.iup.uni-heidelberg.de/
Some good events on ch5 there, eg vtcat -S4 -E4 test.vt:1,2,3,4,5,6 | vtsgram -p100 | display http://abelian.org/vlf/tmp/170709a.gif Now to measure the noise floor. We can use vtstat -a option for th
