Introduction
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!!
Dish Alignment & Signal Reception
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.
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References
#1. – “RTL-SDR for Radio Astronomy – EM Interference”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-radio-astronomy-em-interference/
#2. – “RTL-SDR for Radio Astronomy – Signal Capture1”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-radio-astronomy-signal-capture1/
#3. – “Radio Astronomy LNA/BPF Testing with NanoVNA”
https://jeremyclark.ca/wp/telecom/radio-astronomy-lna-bpf-testing-with-nanovna/
#4. – “RTL-SDR for Radio Astronomy – LNA/BPF Testing”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-radio-astronomy-lna-bpf-testing/
#5. – “RTL-SDR for Radio Astronomy – Planning
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-radio-astronomy-planning/
#6. – “Cheap and Easy Hydrogen Line Radio Astronomy with ….”
https://www.rtl-sdr.com/cheap-and-easy-hydrogen-line-radio-astronomy-with-a-rtl-sdr-wifi-parabolic-grid-dish-lna-and-sdrsharp
