home radio telescope?

Brendano
Brendano
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Topic 194431

would it be possible to convert a 3m satellite tv dish into a usable radio telescope?
brendan

Mike Hewson
Mike Hewson
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home radio telescope?

Quote:
would it be possible to convert a 3m satellite tv dish into a usable radio telescope?
brendan


Hmmm ...... some thoughts :

- the key thing with all electromagnetic telescopes is the aperture/width of the device vs the wavelength you are listening at, and intervening absorption b/w source and detector.

- satellite TV dishes are really in the microwave region. That is they pick up and focus the energy from the geostationary satellite using an aperture many times the wavelength used. Otherwise the signal won't rise sufficiently above noise, and won't point well to select one satellite vs another nearby. The geostat orbits are pretty full thesedays.

- for decent astronomical microwave/infrared work you have to get the atmosphere out of the road, thus into space.

- for the above reasons of atmospheric absorption you can go to longer wavelengths. This automatically scales up the aperture to maintain signal power and angular resolution.

Having said that I've heard of it done in about that size - parabolic backyard jobs so to speak.

As you're ultimately going to be measuring a voltage/current it's worth emphasising the need for a good ground plane and comparing against that. Much atmospheric behaviour will induce a response from such dishes, and likewise the ground beneath. So if you want to enhance detection of distant rather than nearby stuff you'd want to enhance/select the differential between dish and ground - and not their common variation. Alot of advice about attennae doesn't talk enough about grounds ie. what is your voltage reference.

Of course your physical proximity to terrestrial transmitters at your chosen band is crucial otherwise you'll never pick up anything cosmic - the radio equivalent of light pollution. After all it is a satellite TV dish ..... :-0

Cheers, Mike

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Martin Ryba
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I do believe that several

I do believe that several dishes have been repurposed for "backyard radio astronomy," and used by high schools and the like for science teaching. You should be able to observe things like lightning on Jupiter and maybe a couple nearby pulsars with this setup. Because the dish is a parabola, it is fairly frequency independent, so it will work at much lower frequencies than the C-Band (5 GHz) it was designed for (at least down to about 1 GHz). The trick will be to build/obtain a "feed" that takes the concentrated radio energy at the focus and couple it into a coaxial cable to which you can connect a Low Noise Amplifier (LNA).

Try some of the ARRL (Amateur Radio Relay League) "ham" sites for tips and equipment sellers.

Another issue is tracking; I think most old home satellite systems will track in only one dimension since all the GEO satellites are in a belt about the equator. When the dish was installed, it was lined up so the motor could move it along the appropriate line to the accuracy you needed to get the TV signal. I doubt you want to spring for engineering an AZ/EL mount.

"Better is the enemy of the good." - Voltaire (should be memorized by every requirements lead)

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