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cassbeam

Models Cassegrain dish antennas — the microwave and radio-astronomy case

What it does

Computes the beam pattern of a Cassegrain reflector antenna from its geometry -- primary and secondary dimensions, feed pattern, blockage, surface accuracy -- and reports aperture efficiency, gain, sidelobe structure and cross-polarisation.

Why you would want it

Wire-antenna modellers cannot do reflectors at all: the geometry is continuous surfaces and the physics is optical rather than method-of-moments. If you are working on a dish -- EME, microwave, a repurposed satellite antenna, small-scale radio astronomy -- this is the tool for the question "what does this feed actually give me on this dish".

Before it will work

The dish geometry and a description of the feed pattern. Neither is guessable; measuring or obtaining the feed pattern is usually the hard part.

How it installs

  • apt: cassbeam

Known problems

It depends on fftw2, the 1998-era FFT library, which is the same dependency that makes glfer fragile in this catalog. Both still resolve on all five x86 targets as of 2026-08-28, and cassbeam is part of why fftw2 survives in the archive at all -- but it is a dependency on borrowed time, and when it goes this package goes with it. Prime-focus and offset-fed dishes are not Cassegrain geometry and are outside what it models.

Keeping it current

  • probe: apt policy
  • strategy: apt_upgrade

Where to get help with the software itself

The Radio Astronomy Techniques and Technologies group's repository. This comes from radio astronomy rather than amateur radio, which is worth knowing when reading its terminology.

Source: catalog/packages/cassbeam.yaml