Notes and resources on Amateur Level Radio Astronomy

Main Web Sites for Radio Astronomy Site Link
British Astronomical Association Radio Astronomy Group - New Web Site
UK Radio Astronomy Association
National Radio Astronomy Observatory - The Science of Radio Astronomy


The electromagnetic spectrum covers a range from almost 0Hz up to 2.4×10E23 Hz (Gamma rays). Visible light makes up a small fraction of the total spectrum. Obviously visible light is covered by normal optical telescopes. As we already know radio telescopes exist to cover the 'non-visible' radio portion of the spectrum.

For the 'radio' portion of the spectrum this can be further divided into ranges as illustrated below, as allocated by international standards.


However for radio astronomy the radio waves obviously have to penetrate the Earths atmosphere, just like visible light for conventional telescopes. But the Earth's atmosphere is not transparent to all radio frequencies. It is opaque to a large proportion. In fact it is only transparent to a range of wavelengths from approximately 1cm to 1m, the rest is all absorbed by the upper atmosphere.




At the lower end of the radio spectrum frequencies are generated by natural phenominen like lightning and obviously by deliberate radio transmissions. Of course the same range of frequencies that cannot penetrate the atmosphere from space cannot radiate out. At low frequencies they are actually reflected too different extents by the Ionosphere as illustrated below.

For frequencies that penetrate the atmosphere we can point our radio telescopes outward of course. For transmitted frequencies that stay within or are caused by events in the astmosphere, we can still use a receiver to monitor any outside influence that may affect the transmission of those waves, as they can be dependent on the ionosphere. The ionosphere is affected by Solar activity - the Solar Wind - has an effect on the Earths magnetic field and the ionosphere. Also any object which penetrates the atmosphere and burns up causes more ionisation and can affect radio transmissions.

These effects on the ionosphere can increase or decrease the distance to which these lower reflected frequencies are transmitted, so measuring the strength of radio signals over time can give an indication of changes in the upper atmosphere. Beacons, such as time signals, that transmit constantly at a fixed given power are usefull in this respect. Small receivers operating at very low frequencies can easily be built for this purpose.


Below is a table of frequencies that can penetrate the atmosphere and tend to be reserved for radio telescope use, that is not to say there would be no interference from other sources. There are other frequencies at the higher end not in this table, these are the frequencies that could be practical to work with for amateur radio astronomers.

Radio astronomy use
13.36 - 13.41 MHz  
25.55 - 25.67 MHz  
37.5 - 38.25 MHz Continuum observations
73 - 74.6 MHz Solar wind observations. 
Continuum observations.
80.5 - 82.5 MHz Pulsar observations
150.05 - 153 MHz Continuum observations. 
Pulsar observations. 
Solar observations.
322 - 328.6 MHz Continuum observations. 
406.1 - 410 MHz Continuum observations. 
Pulsar observations.
608 - 614 MHz Continuum observations. 
1400 - 1427 MHz Spectral line observations
21cm hydrogen line
1660 - 1660.5 MHz VLBI
1660.5 - 1668.4 MHz VLBI 
Line observations. 
Continuum observations.
1668.4 - 1670 MHz  
1718.8 - 1722.2 MHz  
2655 - 2690 MHz Continuum observations
2.8 GHz (10.7 cm)

Solar Flux -

quoting from the Space Weather Prediction Center - "The solar radio flux at 10.7 cm (2800 MHz) is an excellent indicator of solar activity. Often called the F10.7 index, it is one of the longest running records of solar activity. The F10.7 radio emissions originates high in the chromosphere and low in the corona of the solar atmosphere. The F10.7 correlates well with the sunspot number as well as a number of UltraViolet (UV) and visible solar irradiance records."



Reference material Site Link
A Radio telescope
DIY Radio Tel.
FUNcube dongle
How to Start in Radio Astronomy
Radio Astronomy using INDI
Radio Eyes
Radio Meteor Detection
Significant Radio Astro Freq
Space Australia Radio Astronomy
10.7 cm Radio Flux
Open Source Radio Telescopes
Inspire VLF Project
S. McGreevy VLF receiver
KiwiSDR 10KHz to 30MHz Web Interface SDR
Hydrogen Line
GQRX Software
Convert wavelength in centimetres [cm] to megahertz [MHz]
Solar Drift Scan Techniques
UK Microwave Group
Hawkesbury Radio

Remote Radio Telescopes - SALSA

SALSA means "Such a lovely small antenna". This site provides access to three remotely controlled radio telescopes after you create an account. Works mainly in the Hydrogen Line region of the electromagnetic spectrum.

Title Site Link