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back to article Boffins use lasers to detect radio waves

The universe is a noisy place, if you're a radio signal: travelling through space, there's everything from the cosmic background radiation to the screaming noise of stars and galaxies; travelling through copper wires, there's the random noise that makes weak signals hard to detect. Researchers from the University of Copenhagen, …

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B-D

A brilliant mix of existing tech and ideas for what is essentially a digital radiowave microphone with the diaphragm acting as a platter upon which a laser tone arm reads the peaks and troughs.

Superb.

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"A brilliant mix of existing tech and ideas for what is essentially a digital radiowave microphone with the diaphragm acting as a platter upon which a laser tone arm reads the peaks and troughs."

Correct.

First seen here

in the 1940s

Perhaps the NKVD should get a co-development credit?

but using lasers to detect radio waves by the physical motion induced in a passive receiver.

That is neat.

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Re: First seen here in the 1940s

... indeed, quite a sucessful way of generating scientific output is to trawl through old journals, and re-attempt what failed back then, but with today's technology. (not saying that's what happened here, mind you).

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Re: First seen here in the 1940s

"... indeed, quite a sucessful way of generating scientific output is to trawl through old journals, and re-attempt what failed back then, but with today's technology. (not saying that's what happened here, mind you)."

Actually the device worked fine for spying on the American embassy in Moscow.

What they have done is shifted from audio --> radio to radio --> light, which is a nice piece of lateral thinking.

The clever physics bit is working the maths to realize that this gives much better receiver performance than a straight electrical receiver element.

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I wonder what band they're using … they talk of 1MHz, I was half expecting it'd be microwave stuff. It'd be nice to have a HF radio working with one of these, but I'll bet the price will be eye watering at first. Guess I'll just make do with the FT-857D for now.

This I see having big uses when optical computers come on the scene as the basis for RF PHY interfaces. They need to implement an all-optical DSP and voilá, instant receiver. Then there's just the problem of transmitting, would such an antenna radiate all that well?

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Pint

Neat!

Should be extendable, too.

Beer, for a nice bit of practical science :-)

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Anonymous Coward

Re. Neat

Interesting approach.

Wonder if I can build a DIY variant of this as a home SETI setup?

In this case using a satellite LNB but adding a nonlinear crystal ie lithium tantalate and a laser interferometer to downtune the module to the waterhole band.

IIRC satellite is ideal for this as it already has the appropriate tuned circuits, MMICs and other bits.

AC/DC

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Clever

But I challenge the assertion 'not using antennas at all'. The aluminium foil is an antenna. It's even a resonant antenna.

Any resonant antenna will give improved selectivity in a high-noise environment. It is the band-selectivity of the antenna that rejects the ambient noise. And mechanical resonances have been used for narrow-band selectivity before - like in SAW filters.

That does not mean I am not deeply impressed by the idea of making an antenna sensitive enough to generate significant mechanical movement from the incident wave - to actually take mechanical energy out of the radiation. I will also cheerfully admit that the fact it gives higher than normal sensitivity is entirely contrary to what I would have naturally assumed. Fantastic effort, lads! Have a gold star.

All new developments in Radio are proper advances in technology. This is far more like science than e.g. dreaming up sliding unlock controls on a touch screen. Look, patent trolls - this is a proper advance!

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I was sceptical at first, but reading the article, this looks very interesting. An antenna noise temp of 40 millikelvins is not to be sniffed at!

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Anonymous Coward

Looks like a superheterodyne receiver using light.

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There is, indeed, nothing new under the sun!

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tuning

so how do i change the frequency to receive different bands ? multiple ribbons ?

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Boffin

Re: tuning

Cat's whisker?

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Can this be retrofitted to radio telescopes?

IANAAstronomer so I have no idea if this trickery is in any way suitable, I'm just curious.

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What's the noise figure in dB?

Usually the noise figure for receivers is expressed in dB. What's the noise figure for this setup?

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