Quick progress update on the proof of concept for online observations. I've got the telescope movable, but I'm waiting on a new sdr to get here from china before I can work on the actual telescope part of the telescope. The rtl-sdr I was using before was the casualty of a rogue 12v wire taking out my pi 5 :( barely had it a year so now it's running on a 3B
My system has a strange behavior. In the random moment, there happens a harmonics. I’ve tried different sdrs and lnas - rtlsdr v3, v4, Pluto SDR, nooelec sawbird+ h1, htool ht004. I’ve tried different antennas - tplink wifi antenna, circular waveguide with 1.5 parabola. My coax is RK50-7-11 with N connectors. I have tried to power my sdr from pc, usb power supply, power bank and to power my lna with bias t (from sdr, transformer) and without (from power bank).
I have tried:
Turning off the electricity at home - didn’t helped
running entire setup on the street far from home without coax with my laptop - also didn’t helped
make an rfi with my phone making a call, with my baofeng on 433 MHz and with my icom ic78 - phone calls and icom ic78 doesn’t affect, transmission on 433 MHz near the cable or antenna makes the noise floor higher. But it doesn’t behave like on the video
pointing my waveguide to the floor - the problem keeps appear
using an 15db attenuator before the sdr - didn’t helped.
I live on the outskirts of the small city with ~150.000 population in the private house. The antenna is about 10 meters from the house and about 30m from the nearest neighbor.
The problem begun appearing since the autumn 2025. It appears only with an enabled LNA.
During the half of the year I haven’t found any reasons or methods to solve the problem.
Thanks for any help.
This image created with Python with csv recorded drift scans 5/1 - 5/8/26, from Spectraview, “Hydrogen Line Radio Terrain," represents the results of drift scans performed using a radio telescope. The plot visualizes the detection of the Neutral Hydrogen Line at 1420 MHz as the Earth's rotation allows the telescope's fixed beam to sweep across a portion of the sky.
Breakdown of the Visualization
Vertical Axis (Z): This shows the Relative Hydrogen Signal (dB), indicating the intensity of the hydrogen emissions detected during the scan.
Horizontal Axis (X): Labeled as Drift Time, representing the duration over which the data was collected as the celestial objects passed through the telescope's field of view.
Depth Axis (Y): Labeled as Azimuth, which corresponds to the specific horizontal direction (between 75.00 and 77.00 in this view) the dish was pointed toward during the observation.
Color Scale: The "terrain" uses a heatmap where brighter yellow peaks represent the strongest signal intensities (reaching above 0.7 dB), while darker purple and black areas represent lower signal levels.
Technical Context
This specific data was generated using a 4.5-meter mesh dish. The prominent "mountain" in the terrain map illustrates the concentration of neutral hydrogen, from a section of the Galactic Plane (Milky Way), passing through the antenna's 34 dB gain beam. This type of 24/7 monitoring and data mapping is used to visualize the structure and density of our galaxy.
Recorded in Spectraview Plotted with Python Detected with a 4.5M radio telescope, 1420 tuned and filtered LNA, gain block and RSP1A.
#hydrogenline #radioastronomy #astronomy #radiotelescope
