{"id":6372,"date":"2022-07-21T13:52:32","date_gmt":"2022-07-21T17:52:32","guid":{"rendered":"https:\/\/jeremyclark.ca\/wp\/?p=6372"},"modified":"2025-12-22T09:54:52","modified_gmt":"2025-12-22T14:54:52","slug":"rtl-sdr-for-radio-astronomy-signal-capture2","status":"publish","type":"post","link":"https:\/\/jeremyclark.ca\/wp\/telecom\/rtl-sdr-for-radio-astronomy-signal-capture2\/","title":{"rendered":"RTL-SDR for Radio Astronomy – Signal Capture2"},"content":{"rendered":"\n

Introduction<\/h2>\n\n\n\n
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Fig.1 Rx Location 52Km North of Toronto<\/figcaption><\/figure>\n\n\n\n
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Fig.2 Wide-band Power <<-70dBm<\/figcaption><\/figure>\n\n\n\n

In the previous five posts, I looked at my receiving equipment used for GOES16, to see if I could re-purpose it for reception of the so called hydrogen line at 1420MHz\/21cm (Ref.1\/5). Over several weeks I tried and experimented with various times\/configurations but was not able to receive the hydrogen line. Finally I took a wide-band power measurement and discovered that my downtown location was extremely hot from an RF perspective at -34dBm! I also located an OFDM type signal at 1440MHz which may have been causing intermodulation due to it’s high level and similarity to the comb I was seeing on my background.

I decided to move the equipment to a location far outside the urban environment. Figure 1 shows the test location 52Km north of Toronto in a farming valley, surrounded by hills. The background wide-band level did not even register on the power meter as shown in Figure 2. This proved an ideal location and I was able to clearly see the line. This has been the most challenging project I have done over the past 2 years!!<\/p>\n\n\n\n

Dish Alignment & Signal Reception<\/h2>\n\n\n\n
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Fig.3 Stellarium Sky View July 21st at 10:28<\/figcaption><\/figure>\n\n\n\n
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Fig.4 SDR# IF Averaging Background Calculation<\/figcaption><\/figure>\n\n\n\n
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Fig.5 SDR# IF Averaging Finished Background<\/figcaption><\/figure>\n\n\n\n
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Fig.6 SDR# IF Averaging Hydrogen Line Signal <\/figcaption><\/figure>\n\n\n\n

Figure 3 shows the Stellarium view of the Milky Way from the test location. I first aimed the dish directly west away from the MW to calculate the background. Note the two spurious as shown in Figure 4 (the old enemy 1420.8 is back!). Figure 5 shows the receive signal minus the background which is stable and very flat. Then I moved the dish to the south east at almost vertical. The Hydrogen line is clearly seen in Figure 6. I followed the excellent procedure as outlined in Reference 6. <\/p>\n\n\n\n

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