Keeping the Radio Sky Quiet: What Radio Astronomy Can Teach Amateur Radio About Interference

Radio amateurs spend a considerable amount of time trying to hear very weak signals buried in noise. Radio astronomers take that challenge several orders of magnitude further, attempting to detect extraordinarily faint natural radio emissions that may have travelled across the Universe for billions of years. Unfortunately, both communities share another familiar problem: radio frequency interference.

A new article from the International Telecommunication Union (ITU) examines how radio astronomy can mitigate RFI and draws on the newly revised Report ITU-R RA.2126-2, “Mitigation techniques relating to radio frequency interference into radio astronomy.” The 2026 report recognises that the radio environment is becoming increasingly congested and explores techniques that can allow useful astronomical observations to continue despite interference.

Prevention Is Better Than Trying to Remove It Later
The challenge for radio astronomy is formidable. Astronomical signals can be incredibly weak, while interference can originate from terrestrial transmitters, electronics and increasingly from satellites. The ITU notes elsewhere in its current radio astronomy series that interference can reduce receiver sensitivity, generate false detections and consume significant computing and researcher time simply identifying and removing contaminated observations.

Mitigation can take place at several stages, including careful observatory and receiver design, filtering, identifying and flagging contaminated data, post-processing and increasingly sophisticated software techniques. But mitigation is not magic. Removing interference can also mean removing valuable observations, and some interference cannot be cleanly separated from the wanted signal. ITU
That has a fairly obvious parallel with amateur radio. A noise source prevented is considerably preferable to spending the next six weekends wandering around the neighbourhood with a portable receiver and directional antenna.

Why This Matters to Radio Amateurs
The ITU work is particularly relevant to amateurs involved in weak-signal communications, EME, microwave, satellite operation, SDR, radio astronomy, propagation research and interference hunting.

Many of the techniques and principles are familiar. Good receiver dynamic range, appropriate filtering, clean transmitters, reducing unwanted and spurious emissions, identifying local noise sources and using signal-processing techniques to separate wanted signals from interference all matter when you're trying to extract something very small from a very noisy spectrum.

Modern SDR systems make this even more interesting. They allow amateurs to visualise large sections of spectrum, record signals for later analysis and experiment with digital filtering, noise reduction and interference identification in ways that once required specialised laboratory equipment.

There is also an important spectrum-management connection. ITU-R Recommendation RA.769 establishes detrimental interference threshold levels for radio astronomy, while Recommendation RA.1513 addresses permissible data loss caused by interference in primary radio astronomy bands. Some passive bands prohibit emissions altogether, while other frequency ranges used by radio astronomy receive specific recognition within the ITU Radio Regulations.

A Growing Challenge from Space
The interference environment is also changing. The ITU highlights the rapid growth of large satellite constellations and the impact of both their intentional transmissions and unintended electromagnetic radiation from onboard electronics. Unlike terrestrial interference, satellites can appear above even extremely remote radio observatories specifically located far from conventional sources of RF noise.

These issues are feeding directly into preparations for World Radiocommunication Conference 2027, including studies of aggregate interference from non-geostationary satellite systems and protection of radio astronomy at higher frequencies. ITU
For amateur radio, there is a broader lesson here. A usable radio spectrum depends not only on having access to frequencies, but on keeping the electromagnetic environment sufficiently clean to make those frequencies useful.

Whether we're listening for emissions from a distant astronomical object, bouncing a signal off the Moon, receiving a milliwatt satellite transmitter or trying to decode a weak digital signal, the underlying challenge is remarkably similar:
The weaker the signal we want to hear, the more important good spectrum citizenship becomes.

ITU: How to mitigate frequency interference in radio astronomy - Link

Image sourced from the story.

Page Last Updated: Thursday, 01 Oct 2026 at 21:36 hours by Justin Giles-clark

Click Here To Return To Previous Page