Waterfall and audio clip length


#1

Hi, I’m interested in receiving NOAA transmissions and when I schedule a pass its typically of the order of several minutes. The received waterfall and audio clip that I get see are typically 40 seconds. Why might this be? Is there a squelch level that is perhaps not been broken outside these 40 seconds?


#2

There can be many reasons. Please provide a link to a specific observation where this occurs.


#3

https://network.satnogs.org/observations/520236/


#4

Judging from the audio recording, the sample rate is much lower than what it should be. Perhaps the RPI can’t keep up or there is power supply issue.


#5

Ok, it is an original first generation PI. I’ll try a PI3B I’ve got and see if it makes any different. The power supply should be fine at 2A.


#6

Oh, you definitely need the newer multi-core processors!


#7

I’ve set it up with a Pi2 quad core I have and will see what happens. I ran rtl_test and didn’t see any dropped audio samples. Thanks for your help :slight_smile:


#8

I would strongly recommend the PI3. I think that’s also what the SatNOGS project recommends. rtl_test doesn’t do any DSP so CPU load will increase significantly when satnogs-client starts running DSP software.


#9

Ok, thanks for the advice. I’ve scheduled a bunch of task for this afternoon and evening. Is there any logging I can examine that satnogs-client produces that would indicate if the processor can’t keep up? I am able to decode FT8 and WSPR using jtdx without problems on a Pi2. I appreciate that a PI3 is recommended but the shops are closed on Sunday! :slight_smile:


#10

https://network.satnogs.org/observations/526085/

This observation would at least indicate that the problem of flyover versus audio clip length seems to have been solved by not using a single core raspberry pi.


#11

Yep The single core just can’t manage it.

I did an experiment a year or two ago to try and use a Pi 1 B I had. And it just failed with only 2 min long observations.

I currently use my X86-64 desktop I normally use for my ham stuff for my station. Because generally its not being used and has no load at all.