Observation 1530214: NOAA 15 (25338) Looking for help to improve the received signal

Hello folks,

My station has been working for several weeks and I am trying to improve the quality of the received NOAA images. The power of the signal is changing during the pass and I can’t figure out why.

Example 1:
Observation 1530214
Looking at the waterfall the signal is lost around 140th second then after 300th second, the sidelines of the signal are lost. This is happening in all of my NOAA observations in different forms but in the end, I can’t get a clear image.
Also, there is a broadband noise from time to time. Any ideas what could be the source of this noise - something from my setup or something external and what can I do to remove it, it is present in all of my observations.
Looking at the decoded data - top side of the channel A image is completely white, any ideas why. This is also happening from time to time. I know that channel A image is changing from near-visible to mid-infrared depending on whether it is day or night but looking at other stations that are receiving good images I didn’t find such fully white images.

Example 2:
Observation 1530218
Again the signal is not consistent during the whole pass and there is a broadband noise.

I am using a commercial turnstile antenna TA-1 by Wimo, rtl-sdr v3 dongle and a raspberry 3. Do you think I need a LNA and maybe a filter?

Best wishes,
Ivan / LZ2IPM

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Hi Ivan!. I was reading your post, and regarding the faded noises that can be noticed on both of your shared observations, I could notice that (fortunately) both sat passes are quite similar, and then I thought… maybe is an issue with objects around your antenna system that could be making this problem to appear. When using linear antennas, I could notice that something similar happens just in the middle of the image when the sat pass is around the zenit. This happens because the antenna can’t receive the signal from the satellite properly, but you have a very good antenna, so this shouldn’t come up. Could you share another observation that this issue happen as well, but in a different orientation and/or elevation than the others?. I’ll ask to some folks how they do to get such beautiful images they have.
See you around!. Martin

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Well, I was cheking the other images and the noise seems to be quite random regarding the position of it on the waterfall.

Hi Martin,

Thanks for your reply.
Yes, it seems that the noise is random. At least I cannot find a trend.
Recently I had an observation without such broadband noise Observation 1555729 but still decoded pictures are not good.
I am wondering why the power of the signal is varying so much.