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Radio astronomy

by pseudo
Tags: astronomy, radio
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pseudo
#1
Jan1-08, 06:39 AM
P: 41
while dealing with radio telescopes how can we remove the noise and other disturbances like microwave radiation etc.
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waht
#2
Jan1-08, 11:04 AM
P: 1,636
When you say "noise" do you mean noise induced by man made devices such as cell phones, microwave ovens and washing machines? Or noise caused by amplifying stages of the telescope's receiver?
sysreset
#3
Jan3-08, 11:17 PM
P: 131
I have often wondered the same thing myself. I think pseudo meant radio frequency noise such as radio transmissions. We're bathed in electromagnetic signals: AM, FM, XM, VHF, UHF, Shortwave, GPS, Digital Pager waveband, Mobile Phone waveband, Wireless internet waveband, 2.4 GHz, 5.8 GHz, Bluetooth come to mind. Some of these signals must get out to the large array fields.

pseudo
#4
Jan5-08, 06:43 AM
P: 41
Radio astronomy

Quote Quote by sysreset View Post
I have often wondered the same thing myself. I think pseudo meant radio frequency noise such as radio transmissions. We're bathed in electromagnetic signals: AM, FM, XM, VHF, UHF, Shortwave, GPS, Digital Pager waveband, Mobile Phone waveband, Wireless internet waveband, 2.4 GHz, 5.8 GHz, Bluetooth come to mind. Some of these signals must get out to the large array fields.
there u got me sysreset. there is somthing called as fouriertransform which removes noise . can sm1 tell me how it is used ?
pseudo
#5
Jan10-08, 05:29 AM
P: 41
Quote Quote by pseudo View Post
there u got me sysreset. there is somthing called as fouriertransform which removes noise . can sm1 tell me how it is used ?
radio signals have no atmospheric disturbance. then why does the radio flux has disturbance. why do we use atmospheric extinction for radio flux and not for radio signals.whats d difference ?????
mgb_phys
#6
Jan11-08, 08:51 AM
Sci Advisor
HW Helper
P: 8,954
The main way to remove background noise is to look at very narrow frequency bands.
By having very carefully designed receivers you can look at a faint astronomicla signal at 890Mhz and ignore the cell phone tower next door at 900Mhz.
There are international agreed quiet bands but a big problem is poorly maintained commercial transmitters that generate harmonics or drift out of frequency. Wide spectrum noise sources are a problem, car engines were a pain especially before electronic ignition.

Depending on the wavelength the sky does have an effect. At short wavelengths (high frequency) such as micrtowaves both the signal from the sun and water vapour in the air are a problem and so microwave telescopes are built on the same remote, high and dry sites as optical telescopes - this also gets them well away from artificial noise sources.
Low frequency (long wavelength) are sensitive to large scale waves in the ionosphere whihc cause 'seeing' like the shimmer of atmosphere seen by optical telescopes.
nanoWatt
#7
Jan11-08, 09:51 AM
P: 89
There is also the problem of frequency shifting. Radio waves I believe bounce off the ionosphere, and are slightly shifted.

I think they compensate by looking for lower signals. The interference produces a lot of strong signal lines. By looking for weaker ones, that can eliminate a lot of the interference.
sysreset
#8
Jan11-08, 08:07 PM
P: 131
Is it true that looking at narrow bands of frequency means that we are missing out on unique information carried on the bands we use for commercial purposes? Or is the consensus that the narrow bands give a good representation of what is out there?


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