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Making A Radio Telescope


MeanEYE

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ok so hardware wise what exactly do we need

i had a look at the ittybitty scope a while ago so is the hardware going to be based on that?

i would imagine we would need

sky satlight dish

LMB (how many outputs 2 or 4?)

motor and encoders for altitude

motor and encoders for alzimauth

(i have visions of wixeys and gemreds now:P)

a sort of lazysusan with rail track system

next how does the dish connect to the computer? would we need a receiver like a usb tv tuner? there is a professional one in the RA section but its expensive

the software for viewing a single dish is available at present

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Anyone got any idea of the cost for all this stuff from scratch assuming we have nothing at all?, I am starting to feel a bit deflated, I'm starting to feel this project maybe above me financially and intellectually.. All this talking of tracking using a pulsar or TV line time-base 15.6KHz signal and PLL and GPS not being accurate enough... This is all sounding like the realms of professionals not mere mortals like me, I'm trying to keep up but its getting way out there. :mad: . I should have seen it coming....

I mean, how are you going to synchronise all these dishes? even with some fancy time piece getting everyone to be out there ALL at the exact same time (i'm assuming this cos i don't really understand it) pointing to the exact same spot in space... Now that's going to take some doing i think (but i'm just a mere mortal)..Don't get me wrong i would love it to work i think it could be really something big here a real achievement and i really want to be part of it but i think its getting away from me :clouds1:

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Jumping back onto here from the array bit for a sec...

my gut feeling is we are trying to run before we can walk. Everything I have read so far suggests that a simple satellite dish / LNB will detect the sun, moon, terrestrial and man-made orbital sources but not a huge amount more - the signal : noise ration in a standard dish / LNB setup is too great. There are two ways to get around this: 1) more signal (bigger dish) and 2) less noise (better LNB & decoder). Lovell and other major dishes use liquid gas (N2, I think?) cooling; this is clearly not practical for a DIY setup but a peltier cooled solution with a well insulated LNB & decoder and a blown heat-sink should help.

Exactly how big a dish we need and how much we need to cool it, which are the best LNBs, what is the best circuit design to use, etc. can only be found out by experiment.

I suggest we concentrate on getting a single dish to work very well (can we sink funds together for this, or try multiple competing systems?) and not worry about getting multiple dishes synchronised just yet (there is not point having a hundred dished aligned perfectly if all they are recording is noise). For initial experiments, there is nothing stopping us making a simple manual mount - something like a dob mount would probably be fine - and pushing it around by hand or with a simple servo mechanism.

I have been having a look around for dishes and we can get a nice 1.8m solid dish for about £50; the LNB would be the same again; allow the same (guess) for the decoder components and the same again for the dob base bits (I'm sure Moonshane could advise here). Total cost for first prototype around £200. Add another £100 for insulation and cooling and we might just have something sensible for around £300.

Any takers?

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Sounds interesting I have to say :) I'm happy to carry out experiments with Peltier cooling as I'm already well into this for DSLR cooling. I have several ex-PC PSUs available that can supply the power. I would need some details about the thing that needs coling - the size and the amount of heat it generates.

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Gina,

the bits that will need cooling are the LNB, the box of electronics that takes the LNB output, drops the frequency and amplifies the signal and the cabling between them. The LNB is a bog standard one and I would guess the electronic wizardry can fit into a small box (think a broadband router or similar - this can probably be shrunk down if we get to printed circuit boards). Harder to judge heat input; we just need to get rid of as much ambient as possible to reduce internal noise.

My gut feeling is that we will end up combining the LNB and electronics into a single box.

J.

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Hmmm.. I haven't been able to be on here much in the last few days and what do I see when I come back? Another great and interesting project.

Count me in .. ;-)

I could help on the electronics side and I can also do a bit of coding (I have limited experience in C# and C++).

I'm not quite sure on the signal we would get from the LNB / sensor? Would this be equivalent to a single pixel compared to "normal" imaging and we would need to move the dish in very small steps to get an actual "image"?

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Should also look at reducing the number of noise generators in the vicinity of the detector, i.e. no powerline Ethernet nearby! Plus shielding of any attached processing equipment etc. might it be a good idea to power all equipment from DC to avoid any RF pollution from the mains?

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what kind of signal or image are we going to get from the dishs, i really want to do this project but realisticly im just pushing out the negitives just to make sure we know what we are going to get into.........

what do we get from the moon, jupitor sun ect? this is a fantastic project and one that can bring ameratures all over the world into one

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@garethnob - that would be half the fun, finding out what emits at the wavelengths we are detecting! At the moment, my RF view of the universe is blank, "looking" though a radio telescope will start to colour it in for me.

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I think it unlikely that much of the electronics will need cooling. Generally it just the detector/sensor and early stages of the amplifier. Once the signal level gets above a certain level the thermal noise becomes unimportant.

I do agree that RFI needs to be kept out and that all early stages need screening and the power supply well filtered. I have some experience of radio receivers up to VHF/UHF. The only experience of SHF is the repair of an old radar set.

What is the wavelength of the radiation we are interested in?

Seems I need to do some serious reading :D

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cost is still to much.

£300 is pushing to a decent sw 150 /200 scope.

cheapest i made it was maplins.

LNB £14

Signal meter £14

dish £40 ( could get less if hunt carboots etc etc)

add another £10-20 for bits an bobs. you could get a full settup for around £40-70

cooling is fairly simple, a mid sized TEC unit mounted to the alloy box bodywork of the LNB.

LNB's tend to be weather sealed, you remove outer plastic and confronted with the internal alloy casing,

and horn. a smallish hole made into the LNB plastic casing allowing a heatsink to poke through.

stripping the LNB leaves it open to possible noise from other areas, the alloy case acts as a shield.

going for a close by object is more simple than an object way beyond our reach. start close and expand on that.

we use a small bank of scopes unlike the 3-10m dishes used by the pro's. so closer an object we have more chance of getting readings from.

the readings tell us if its working and how well.

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@garethnob - that would be half the fun, finding out what emits at the wavelengths we are detecting! At the moment, my RF view of the universe is blank, "looking" though a radio telescope will start to colour it in for me.

Very good question - anybody know what frequency LNBs are optimised to? Can they be changed by varying the IF? If so, what range is feasible? Will dig online...

Quite a useful list of interesting frequencies here: http://www.ukaranet.org.uk/basics/frequency_allocation.htm.

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Very good question - anybody know what frequency LNBs are optimised to? Can they be changed by varying the IF? If so, what range is feasible? Will dig online...

Quite a useful list of interesting frequencies here: http://www.ukaranet....allocation.htm.

An interesting list :)

OK so we are thinking in terms of modifying a satellite television receiver to work outside the TV band - obviously no good within it as we'll just get broadcast TV. The sort of signals we are interested are clearly several magnitudes lower than a received TV signal and therefore need to be well away from broadcast satellite channels.

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I'm with Jammespels - let's not get too carried away with fine details just yet - I trhink it's about all having a tinker at the moment and seeing what we can come up with - at the end of the day different people will have different ideas and designs, some of which will be better than others. If we all have a little go on our own first, it'd be like a big crowdsourcing job - the pooled experience we got would vastly outweigh what any one of us could do. Also, at the moment, none of us really know anything about Radio Astronomy - at least not from the point of view of having tried it. We all do a lot of reading and even more talking (well, typing), but really, we're all in the same boat - unexperienced. The only way we're going to change this is by each of us having a poke around and seeing what happens, and learning from our various successes, failures, and by listening to those of each other!

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for the maplins (£14) LNB

Input frequncy range : 10.7-11.7 GHz lowband / 11.7-12.75 GHz highband

Output frequency range: 950-1950 MHz lowband / 1100-2150 MHz highband

L.O. frequency: 9.75 GHz lowband / 10.60 GHz highband

L.O stability: +/- 3 MHz (-30°C - +60°C)

L.O phase noise:

-60 dBc @ 1 kHz offset

-85 dBc @ 10 kHz offset

-100 dBc @ 100 kHz offset

Noise figure @ 25°C: 0.3 dB (typical) both low/highband

Output Vswr: 2.5:1

Conversion gain: 55dB (typ)

Gain flatness: +/- 0.5dB / 26 MHz

Output spurious: -60 dBm

hope this can help with signal strength, the noise figure can be dropped and ignored. once cooled your looking at around -0 /-20c with tec units, even lower in winter.

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Basically, anything that is built to receive at civilian or military frequencies is useless to us - we'll hear nothing over the blare of the channels already in use. However, there is a dedicated part of the radio spectrum reserved for Radio Astronomy. I just can't find it lol!

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Yeah I take that back - it is only reserved from long range transmitters - wifi and things uses similar frequencies, which is getting me thinking.... We're looking at the10 Mhz - 100 GHz range, according to Wikipedia, so just forget my previous! However, my thinking is that if this is the type of frequency wireless networks use, can we possibly tie this into the connectivity issue? Obv wifi is severely range limited, so it's not too hard to get away from, but if we could somehow mod a wifi receiver into an antenna...? Anyway, just some brain food. Summary of this ramble is that Radio Astronomy typically uses the frequencies between 10 Mhz and 100 GHz. Most sources emit across the spectrum, but lots of ferequencies are filled with earth-based interference.

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Yeah I take that back - it is only reserved from long range transmitters - wifi and things uses similar frequencies, which is getting me thinking.... We're looking at the 3-300 GHz range, according to Wikipedia, so just forget my previous! However, my thinking is that if this is the type of frequency wireless networks use, can we possibly tie this into the connectivity issue? Obv wifi is severely range limited, so it's not too hard to get away from, but if we could somehow mod a wifi receiver into an antenna...? Anyway, just some brain food. Summary of this ramble is that Radio Astronomy typically uses the frequencies between 3 and 300 GHz. Most sources emit across the spectrum, but everything else is filled with earth-based interference.

i was snooping around on youtube and likes, came across a chap who converted a sat dish into a wifi dish ? any good ?

could one send and receive signals via a single dish.

answered my own question, yes send and receive, found one build that says a 76km wireless connection via a dish and wifi

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i was snooping around on youtube and likes, came across a chap who converted a sat dish into a wifi dish ? any good ?

could one send and receive signals via a single dish.

Definitely, but they couldn't be signals of similar frquency of would interfere. I wa thinking more of converting a wireless dongle type thing into an antenna that would then be able to plug straight into a computer via USB - then it's all down to software from there....

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