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Discover LOFAR – Low Frequency Universe

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Discover LOFAR and learn about how to search the universe for signals using digital beamforming with simple antennas and computers.

Recently, I came across an article from Cornell University describing how radio signals may have been detected from a nearby exoplanet. Now, nearby is a relative term – in this case 51 light years – but the discovery was a first.

But what really got my attention was this discovery using low frequencies (10 to 240 MHz) using many small antennas and digital beamforming. More on this in a moment.

The signal discovered was not SETI, rather we heard a natural signal from the planet’s magnetic field. To date, 4,000 exoplanets (planets circulating nearby stars) have been discovered. Usually, exoplanets are discovered visually by the transition across a star or by doppler effect from gravitational interaction.

When you discover LOFAR, you discover that scientists are now using Jupiter’s magnetic field emissions as a template to search for exoplanet magnetic signatures 40 to 100 light years distant.

LOFAR lets you use many small antennas to study the universe at HF/VHF/UHF frequencies, rather than microwaves. Take a look at how it works.

Discover LOFAR – Beamforming in Action

LOFAR is a low frequency array covering 10 to 240 MHz. I discovered LOFAR built in Europe with 20,000 small antennas (see above) at dozens for stations. As with my recent experiments with arrays and beamforming, received signals are not combined at the antenna, but rather in computers.

Essentially, I discovered a software defined radio telescope, using 12 bit ADC sampling at 160 or 200 MHz. (By comparison, my Flex 6300 uses 16 bit ADC at similar sampling rates.) Data is buffered from various Nyquist zones and filtered down to 200 kHz sub-bands for combining with digital beamforming.

From LOFAR, bandwidth is down-sampled to 1 kHz channels. With beamforming across hundreds of small antennas, you achieve fields of view between 3° to 7.5°.

If you have read my recent articles on beamforming and active antenna arrays, you will realize that LOFAR is using these same techniques to measure radio signals from exoplanets. The difference is only in scale, with thousands of antennas being steered across the sky rather than just two, like mine!

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