<p>Background:  I am attempting to build an RTL-SDR-based radio telescope for detecting hydrogen lines (21 cm) as a project with my HS Physics class. Several accounts are online, including parts lists and assembly instructions, and I am reasonably confident that I can get it working in a stationary &quot;Scan as the Earth turns&quot; mode.</p>
<p>How big a patch of sky will we be &quot;seeing?&quot;  If I view the celestial equator continuously and average the reading over 10 minutes, I will have 144 pixels or &quot;buckets&quot; of 2.5 degrees width.   The receiving antenna I am starting with is a commercially available WiFi antenna.</p>
<p>(2.4GHz 24DBI Directional High-Gain N-Type Female Aluminum Die Cast Grid Parabolic Antenna (ANT-GRID-24DBI))</p>
<p>with this listed</p>
<p>&quot;Beam width/horizontal: 14 Beam width/vertical: 10 F/B ratio-db: &gt;30&quot;</p>
<p>Does the beam width mean I am looking at &quot;buckets&quot; of sky either 10 or 14 degrees across?</p>
<p>Is this 10-degrees the half-power beam width or the first null beam width?</p>

CC BY-SA 4.0
2024-04-22T14:13:04.067Z
A WiFi antenna (designed for 12 cm wavelength) will not perform well at 21 cm.
John Doty
CC BY-SA 4.0
2024-04-22T18:33:57.277Z
A very interesting project.  Is it possible to follow its development somewhere?
ayr
CC BY-SA 4.0
2024-04-22T20:02:50.317Z
https://lweb.cfa.harvard.edu/~npatel/hornAntennaAASposterPDF2.pdf Could be of interest - build your own cheaply…
Jon Custer
CC BY-SA 4.0
2024-04-22T20:43:48.267Z
@dtn The original article inspiring the project is here

https://www.rtl-sdr.com/cheap-and-easy-hydrogen-line-radio-astronomy-with-a-rtl-sdr-wifi-parabolic-grid-dish-lna-and-sdrsharp/
Stan Forrester
CC BY-SA 4.0
2024-04-22T20:44:50.700Z
@Jon Custer  Thank you for the resource.
Stan Forrester
CC BY-SA 4.0
2024-04-23T01:26:11.640Z
https://physicsopenlab.org/2020/07/20/horn-antenna-for-the-21cm-neutral-hydrogen-line/ As well. Seems there are quite a variety of people who want to do something similar, so a little googling may go a long way. Excellent project, perhaps you could find a local ham radio operator/club to assist. The Amateur Radio SE may answer questions as well.
Jon Custer
<radio-astronomy>
DIY Radio Telescope (High School)
Stan Forrester
# DIY Radio Telescope (High School)

(Asked by: username_0 on 2024-04-22)

Background: I am attempting to build an RTL-SDR-based radio telescope for detecting hydrogen lines (21 cm) as a project with my HS Physics class. Several accounts are online, including parts lists and assembly instructions, and I am reasonably confident that I can get it working in a stationary "Scan as the Earth turns" mode.

How big a patch of sky will we be "seeing?" If I view the celestial equator continuously and average the reading over 10 minutes, I will have 144 pixels or "buckets" of 2.5 degrees width. The receiving antenna I am starting with is a commercially available WiFi antenna.

(2.4GHz 24DBI Directional High-Gain N-Type Female Aluminum Die Cast Grid Parabolic Antenna (ANT-GRID-24DBI))

with this listed

"Beam width/horizontal: 14 Beam width/vertical: 10 F/B ratio-db: >30"

Does the beam width mean I am looking at "buckets" of sky either 10 or 14 degrees across?

Is this 10-degrees the half-power beam width or the first null beam width?

**Tags:** radio-astronomy

> **Comments:**
> **username_1**: A WiFi antenna (designed for 12 cm wavelength) will not perform well at 21 cm.  
> **username_2**: A very interesting project.  Is it possible to follow its development somewhere?  
> **username_3**: https://lweb.cfa.harvard.edu/~npatel/hornAntennaAASposterPDF2.pdf Could be of interest - build your own cheaply…  
> **username_0**: @dtn The original article inspiring the project is here  https://www.rtl-sdr.com/cheap-and-easy-hydrogen-line-radio-astronomy-with-a-rtl-sdr-wifi-parabolic-grid-dish-lna-and-sdrsharp/  
> **username_0**: @username_3  Thank you for the resource.  
> **username_3**: https://physicsopenlab.org/2020/07/20/horn-antenna-for-the-21cm-neutral-hydrogen-line/ As well. Seems there are quite a variety of people who want to do something similar, so a little googling may go a long way. Excellent project, perhaps you could find a local ham radio operator/club to assist. The Amateur Radio SE may answer questions as well.  

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## 0 answers

