Observing 21cm Hydrogen line

Over the winter 2013/14 I helped Matija – S53MM to build 3.6m parabolic mesh dish for 23cm & UP EME.  Looking at I1NDP pictures of Hydrogen lines in Milky Way I decided to try to see them too. Afterwords I find nice pictures also on F1EHN home page. Until now I only used his SW for tracking the Moon and did not noticed his radio astronomy projects before.

I was pretty sure, that I can see this lines with USB DVB-T dongle (RTL 2832 & R820T tuner going up to 1.7 GHz) using S53MM EME preamplifier (0.3dB NF and 30dB Gain) and his Septum feed optimized for 23cm EME circular polarization.

I decided to use SM5BSZ Linrad SW. I made SM5BSZ pulse generator to calibrate DVB-T  dongle. I achieved +/- 0.1 dB flat frequency response. Dongles have +/- 0.5 dB response without calibration (or more).

On the Saturday 17. May 2014 we decided to do short observations and than (more important) calibrate his AZ/EL rotor afterwords. This is what I get on my monitor:

H-line cassiopeia-A.jpg


I did't have enough time to optimize my observations. I am sure that I have some room to improve.

Antenna was pointed  some where around  Cassiopeia A source. Two arms of our galaxy with different Doppler shifts are detected.

Trying to find other similar attempts on internet, I found also S57UUU and S57RA pages with quite serious radio astronomy.


New feed tuned for 1420 MHz:

2014-06-08 16.25.54-small.jpg


Results are better for 0.3dB compared to septum feed tuned to 1300 MHz

Galactical coordinates L=70 De=0 with a new feed. Diagram made on 15.08.2014.

70 stopinj-1.jpg


Galactical coordinates L=80, De=0

80 stopinj-1.jpg


L=90, De=0

90 stopinj-1.jpg


L=100, De=0

100 stopinj-1.jpg


L=110, De=0

110 stopinj-1 drevo.jpg

I also find out that noise is at leest 2dB higher if tree is an obstacle in the way.


Here is picture of Milky Way with coordinates for comparison of my results.



Short video when moving antenna.


Moon Noise – 28. 03. 2015

Here is Moon noise (around 0.25dB over cold sky) on 2.3 GHz. I used DB6NT transverter with preamplifier (2.3 GHz to 144 MHz, than Javornik transverter from 144 MHz to 14 MHz and Afedri SDR with Linrad). Antenna is 3.6m mesh parabolic dish. 2.3 GHz picture is a bit messy. Noise can be seen in the last bulge before diagram goes sky high because of ground noise. Than we changed feed to 3.4 GHz for DUBUS 3.4 GHz EME contest.


With similar equipment we than also saw Moon noise on 3.4 GHz. We take a litle more time to do that and picture below is nice now. We measured about 0.3 dB of Moon noise on 3.4 GHz.


High School Research Project (GSŠRM)

In a school year 2017/2018 I was part of research groop (students Špela and Tim, teacher Lojze) in a high school research project From Moon to the Center of Galaxy with radio waves. Text is in Slovene language, but you can find Abstract in English language at the beginning. I made a short film of Hydrogen 21cm lines from pictures that we made on 24. February 2018.

Below is a Map of Hydrogen radial velocities from Galactic coordinates (b=0), L=0 to 255 deg. in 5 deg. steps (made by Špela and Tim). Part of Galaxy from L=260 to L=355 is not visible from our location in Europe. First and last two vertical slices are quite noisy because of low elevation angle of the antenna. Earth noise is kicking in. Relative velocities going from +190 km/s at the top of diagram (moving away) to –190km/s at the bottom (approaching). Dark line in the middle representing velocity 0km/s (frequency 1420.406 MHz).