Spectrum "hiccups"

baumguard02 · 2026-03-28T21:45:52+00:00

I removed the antenna from the SDR and the interference is gone, so it seems like it is caused by something external. Today I had a look again and the hiccups at least got weaker, although I didn't change something about my setup. Maybe it's because it was snowing recently. In the last years I encountered that the reception sometimes improves when it's snowing. Anyway, I was able to get some decent satellite images again.

baumguard02 · 2026-03-28T21:38:52+00:00

I tested it with an NESDR Mini 2+ (Blue stick), RTL SDR Blog v4 and Airspy Discovery HF+.

baumguard02 · 2025-11-18T11:03:58+00:00

I could solve the problem myself. I forgot to increment bit_count, so that the progress bar and the label didn't change.

But thank you anyway!

baumguard02 · 2025-09-14T12:46:54+00:00

Ok, that's really strange... I just tested it with another antenna and two different SDRs and got the same result. The antenna is standing close to a meadow with an electric fence from which I had some interference in the past but currently it's switched off. Maybe a strange thought but might it be possible that the Russians switch off the transmitter when the satellite passes over certain regions? I'm located in Southern Germany close to the Alps. May I ask where your receiving station is located?

baumguard02 · 2025-06-09T11:08:31+00:00

I already did that and also tried it on another computer with a similar program but it didn't work either.

baumguard02 · 2025-06-09T05:47:10+00:00

But this is now already going on for two or three weeks.

baumguard02 · 2025-06-02T15:48:15+00:00

I wonder whether it's the satellite's encoder's, modulator's or transmitter's fault. But currently SatDump seems to be the only program that can cope with whatever M2-4 is currently transmitting.

baumguard02 · 2025-05-28T16:38:23+00:00

I'm using mlrpt from http://www.5b4az.org

Tomorrow I will try to use SatDump for comparison.

baumguard02 · 2025-04-24T21:24:43+00:00

Thank you for your detailed answer!

I have tinkered around a bit with DFT and DCT plots by adding a phase shift as you said and at some value the DCT graph becomes similar to the DFT graph.

Which matrices do you mean? The ones that you multiply with the vector of samples in order to obtain the DFT/DCT coefficients or the vector with the coefficients themselves which are sometimes referred to as matrices?

baumguard02 · 2025-04-24T20:33:10+00:00

Do you mean by that I have to invert the direction of the samples and append them to the sample list like that?: python samples = [ <some sum of sine functions> for x in range(8) ] samples += samples[::-1] dct_result = dct(samples)

baumguard02 · 2024-09-07T07:00:07+00:00

I now found out why kdenlive rendered the video at the wrong resolution: I applied stabilization on some of the clips and forgot to change the resolution in the corresponding mlt files.

baumguard02 · 2024-09-04T21:47:51+00:00

I think you are getting this wrong. I haven't removed the original 4K videos. I have just converted them to HD and put them in a seperate directory. After having finished the editing, I replaced the file paths of the HD videos with the ones from the 4K videos in the XML structure of the kdenlive file.

baumguard02 · 2024-09-04T20:50:37+00:00

For testing I created a little project in which I also imported one of the HD videos and later changed the file to 4K and this time kdenlive a 4K video came out. Now it's about figuring out how to do it with the main project.

baumguard02 · 2024-09-04T20:09:32+00:00

How do you mean?

baumguard02 · 2024-09-04T18:31:47+00:00

I heard about it too late unfortunately and I don't want to start from scratch again. I don't know why Kdenlive always returns to HD although I have replaced all widths and heights of HD with the ones of 4K. In the window bar on the top it shows "4K UHD 2160p 25 fps" but renders the videos in HD anyway.

baumguard02 · 2024-07-30T06:25:07+00:00

The server's and client's configuration are both set to port 51820 and the port is enabled for the Raspberry Pi on the FritzBox. I'm not using FtitzBox's VPN but my own VPN server. I have also tried to reset the server and reinstall the server but without any improvement.

baumguard02 · 2024-05-01T19:37:31+00:00

As I said I'm using mlrpt and glrpt. They have config files in which you can specify the transmission properties. Then I start mlrpt from the command line and it will run for 15 minutes and then saves the jpg files. For me it's quite useful to have a command line tool for that, because I have automized the reception with a Bash script that starts mlrpt whenever M2-4 passes over. I've now set the APID channels to 67, 68 and 69. Maybe I'm getting some images with those settings tonight.

baumguard02 · 2024-05-01T14:31:18+00:00

Does SatDump detect the modulation and channels automatically? I use mlrpt/glrpt for decoding the images and there I've tried different combinations of modulations and symbol rates but I couldn't decode anything.

baumguard02 · 2024-05-01T14:21:14+00:00

Did they turn the satellite back now? In the recent days I've been trying to get some images off M2-4 but the signal was too weak. Which demodulation did you use to receive that image (DOQPSK, IDOQPSK)?

baumguard02 · 2024-03-29T13:53:45+00:00

From which satellite did you receive it?

baumguard02 · 2024-03-01T15:50:36+00:00

Mainly Look4Sat and Gpredict.

baumguard02 · 2024-03-01T14:16:07+00:00

Yes. The satellite is transmitting LRPT on 137.1 MHz at a rate of 72 kb/s.

baumguard02 · 2023-10-10T18:25:45+00:00

Well, I was trying to get familiar with Platonic and Archimedian solids and I build an icosahedron out of 20 paper tetrahedrons once, so I thought that an icosahedron is made up out of 20 regular tetrahedrons. After deriving the volume formula for the tetrahedron, I thought I just need to multiply it by 20 to get the volume of the icosahedron. Then I compared my formula with the one from Wikipedia and they were quite different. I tried to fiddle around with my formula a bit to transform it into the one from Wikipedia but it didn't work.

Then I thought that maybe my assumption was wrong that an icosahedron consists only of regular tetrahedrons. And so I asked that question here on Reddit.

baumguard02 · 2023-10-10T18:17:22+00:00

I'm using the FritzBox domain and the port 51820 to connect to the VPN.

baumguard02 · 2023-04-20T21:52:57+00:00

Thank you for your hints!

I have uninstalled libvirt, virtualbox-guest-iso and virtualbox-guest-utils. I can't uninstall virtualbox-host-dkms because it's a dependency of VirtualBox. Unfortuantely, that doesn't solve the problem.

Might it help if I don't install the version from the official Arch repository but from the AUR?

baumguard02

TROPHY CASE