Radio scope from a 12 inch???

[xelasnave]

I was talking to a mate who is into radio..

we got to talking and it dawned on us that if one were to place a mic where the eye piece is in a scope well one should get radio waves in the same way one will get light rays...

radio is after all elctromagnitic radiation..it is we just dont see it... but it must behave the same as a light wave one would think...so do you reckon we will get anything if we take out the eye piece and place a mic there instead???

I know I am thinking to much ...but its this ladies fault... I lose it more when she is in there.
alex

[Kal (Andrew)]

Microphones don't capture radio waves, they capture sound waves.

Maybe you should stick a radio antenna at the end of your telescope and see if you can amplify 2GB or something

[xelasnave]

Originally Posted by Kal

Microphones don't capture radio waves, they capture sound waves.

Maybe you should stick a radio antenna at the end of your telescope and see if you can amplify 2GB or something

Yes my mate was pulling me up on that...of course a mic wont do it ...
My point is if one had the "point" of receipt at the point of focus (or near it given it probably would focus maybe a little different) could one record the radio wave in this arrangement.

alex

[Bassnut (Fred)]

I dont think glass reflects radio waves (umm, I know it doesnt) .

A wire grid would, and much cheaper than glass , but then youd have to build from scratch.

[netwolf]

A silvered mirror will reflect Radio waves. A ocean wave to a Tea cup saucer would smash through and not even notice the saucer. The larger wave length of a RF wave would require a bigger surface to produce a result. Given it is a bigger wave the surface does not have to be a solid it can be as Fred pointed out made of chicken wire mesh. For Microwave as its smaller wave you need a more solid surface.

Also as rightly pointed out by Kal you would need a Feed Antenna at the focal point to convert the EM wave to an Electric current that you can detect. For the microwave spectrum they use a waveguide to pikcup the signal and convert it to electrical currents.

[TrevorW]

Thats why radio wave collectors are so big !!!

[netwolf]

One of Maxwell's equation gives the reason why a perfect or even a good conductor can reflect EM waves (with a phase change). This essentially states that the magnetic flux is zero on the plane of a conducting surface, therefore the energy is reflected with a phase change to maintain the boundary condition. This means that even the surface of the earth reflect EM waves. As such you can and i think they have built large reflectors using craters or natural valleys between mountains. The earth acts as the reflector.

[xelasnave]

My point was somewhat that we (maybe just me of course) when we think of light dont see it as part of the spectrum...

But I have no intention of taking this further...I did ask a chap about building a "radio" scope and he said just get a "wok" I thought it was something DickSmith sold to radio buffs but he meant a cooking wok.

alex

[netwolf]

Alex more interestingly we humans seem to have the right sensor (our eyes) to detect this particular spectrum. Perhaps why we dont given it much thought. And our skin is sensitive to some of the invisible spectrum. I wonder on some other planet how live might evolve if visible light was a premium.

[Wavytone]

Three problems
- aperture is too small,
- the focal ratio far too slow,
- the first stage detector must be cryogenically cooled .

By way of example there's a small parabolic dish outside the Australia Telescope maybe 1 metre across, with a focal ratio of f/0.5 with an antenna feed hooked up to an amp. Swishing it across the sky you get an audible hish from the sun and I suspect at night it might just detect Jupiter. Not a whle lot else.

BTW to do much good the mirror aperture must be many times the wavelength of the radiation. This is why serious radioastronomy dishes are huuuge.

So don't bother with a scope mirror... it won't work.

[bmitchell82 (Brendan)]

SKA say no more!!!