Hydrogen Line Band Interference

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MMcC
Posts: 6
Joined: Fri Jun 04, 2021 5:01 am

Hydrogen Line Band Interference

Post by MMcC » Fri Jun 04, 2021 5:34 am

I have an RTLSDR connected to a Yagi antenna. It seems to work well, enough to pick up what appears the be the Hydrogen Line. The 1.420GHz range is meant to be protected from interference, but I am seeing weak signals right across the band. These disappear when the antenna is removed and some of these weak signals don't appear to have directionality.

First image (SE direction)
Image

Second Image (SE direction - a few hours later)
Image

Third Image (NNE direction - a few minutes after the second image)
Image

I know it is hard to diagnose, but I'm interested in any ideas.

rtlsdrblog
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Joined: Mon Nov 19, 2012 11:54 pm

Re: Hydrogen Line Band Interference

Post by rtlsdrblog » Mon Jun 07, 2021 5:37 am

I'm not seeing any Hyrogen line there unfortunately. Those tall peaks are just noise, or the center DC spike.

It's really unlikely that you're getting the Hline without a good LNA. The Yagi will also need to be tuned for 1420 MHz, and pointing at the milky way to have any chance at seeing something.

Take a look at https://www.rtl-sdr.com/cheap-and-easy- ... -sdrsharp/ to see what the peak should look like.

As for the noise, I'm not sure. It could be out of band noise mixing in. Using the Sawbird LNA+filter will help in that case. Also using a more directional antenna like a dish can help too.

MMcC
Posts: 6
Joined: Fri Jun 04, 2021 5:01 am

Re: Hydrogen Line Band Interference

Post by MMcC » Mon Jun 07, 2021 6:40 am

I ran IF average and get a similar peak, although it is smaller due to the lack of tuning.

rtlsdrblog
Site Admin
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Re: Hydrogen Line Band Interference

Post by rtlsdrblog » Thu Jun 10, 2021 2:47 am

MMcC wrote:
Mon Jun 07, 2021 6:40 am
I ran IF average and get a similar peak, although it is smaller due to the lack of tuning.
Got a screenshot?

MMcC
Posts: 6
Joined: Fri Jun 04, 2021 5:01 am

Re: Hydrogen Line Band Interference

Post by MMcC » Fri Jun 11, 2021 5:08 am

This is from a drift scan. I don't entirely rule out interference, but it is hard to see where it would be coming from.

Image

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