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I have a small antenna and radio system that can receive frequencies between 1MHz and 1GHz. The system has a discone antenna. I plan to do some aperture synthesis based on the daily rotation of the Earth that will allow me to resolve a lune with a width of about one degree.

What objects and specific frequencies should I observe to test to see if the system and algorithm is functioning properly?

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    $\begingroup$ Interesting question! By aperture synthesis I think you mean a single antenna's received signal is recorded at several different times as it moves to different locations, and those are combined computationally off-line in a way similar to having multiple antennas at those locations. This works well for radar where phase and coherence of the source is controlled. Can aperture synthesis be used for single antenna receive-only radio astronomy systems? Are there any known examples of this being done with a single antenna? $\endgroup$
    – uhoh
    Mar 11, 2021 at 23:48
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    $\begingroup$ I can do the aperture synthesis only because the antenna is a on the rotating Earth. Like you said, as the Earth rotates, it's as if I have lots of antennas. One limitation is that objects that move faster or slower than the "fixed stars" will look like noise to the synthesis algorithm. I might be able to use different processing techniques to see the faster/slower objects. I don't know of any examples of this being done like this, but I am not really in a position to know that sort of thing. Part of the reason for posting was to see if anyone recognized what I was doing. $\endgroup$
    – Craeft
    Mar 11, 2021 at 23:59
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    $\begingroup$ Yes, and also within my receiver bandwidth, and likely to avoid Earth based transmitters. $\endgroup$
    – Craeft
    Mar 12, 2021 at 0:15
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    $\begingroup$ In 1960s Cassiopeia A, Crab Nebula used to calibrate radiotelescopes. $\endgroup$
    – A. Rumlin
    Mar 12, 2021 at 18:24
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    $\begingroup$ Now that your question has been here for two days I can add a bounty to it. I think it's a great question and am interested in its answer. $\endgroup$
    – uhoh
    Mar 15, 2021 at 1:36

1 Answer 1

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The following table is based on The measurement of large antennas with cosmic radio sources (sorry for the paywall), Table I "Radio Sources for Antenna Measurements", Panel A "Flux Density and Polarization Data". This table contains some of the brightest "point sources" at microwave frequencies. I have extracted only the flux densities at 1 GHz to match the requested frequency range in the question. Flux densities below 1 GHz will be different.

Source Flux Density (fu)
Cassiopeia A (Cas A, 3C461) 3185 $\pm$ 30
Cygnus A (Cyg A, 3C405) 2270
Taurus A (Tau A, 3C144) 986 $\pm$ 12
Virgo A (Vir A, 3C274) 285 $\pm$ 5
Orion A (Ori A, 3C145) 330
Hydra A (3C218) 60
Hercules A (3C348) 62
3C353 73
DR21 4

1 fu = 10-26 Wm-2 Hz-1 = 1 Jy

Locations are epoch 1950.0.

For a home system these are still likely to be very small signals. Using the sun as a reference source may be a better choice even though it is "extended" and the location changes rapidly. Whether you consider it extended or not of course depends on your angular resolution.

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    $\begingroup$ This is a good answer, although 1GHz isn't clear of terrestrial transmitters. I'll give it a try and see what happens. Thanks! $\endgroup$
    – Craeft
    Jan 10, 2022 at 17:14
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    $\begingroup$ @Craeft If you can go somewhat higher in frequency above 1 GHz there are some protected bands. I'm not as familiar with lower in frequency. $\endgroup$
    – GrapefruitIsAwesome
    Jan 10, 2022 at 17:39

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