DIY Radio Astronomy Project

bloodhound31 · #1 13-09-2006, 07:39 PM

After some cloudy nights in my new dome, I thought I had better make use of this new retreat I have made for myself. So began some research on getting started with radio astronomy. I have built an antenna, (nearly finished), and am looking at a nice little $50 reciever to listen to HF bandwidth approximately 15 to 30 mHz. Jupiter is a relatively simple target, as is the sun. Jup's is at about 21.9 mHz.

Heres a couple of pics of the antenna in the works.

I will probably add this project as a new page on my website so you can have a look as it progresses. http://members.iinet.net.au/~armstead

I', just starting and know practically nothing about it, but its loads of fun!!! Like to hear ideas and suggestions from others in the same game!

Cheers,

Barry

ballaratdragons (Ken) · #2 13-09-2006, 07:42 PM

I quite enjoy Radio Astronomy! I have read many sites on how to build a home set-up but have always been put off by the amount of gear needed for even a simple set-up.

Yours sound simple!

I used to use the one at the Ballarat Observatory, but they threw it out!!!

bloodhound31 · #3 13-09-2006, 08:31 PM

Mate, just have a quick hunt around google for home made radio telescope antenna and related, you will be amazed at the things you have in your shed that can tune in to the stars! I have just found out that there is a pci card that can do the job, or if you have a laptop, there is an external usb device, about the size of a sandwich, to convert ur pc into a reciever for the stars!

Heres a pic of another blokes attempt. works well.

Cheers,

Barry

Astroman (Andrew Wall) · #4 13-09-2006, 08:50 PM

ahh traditional open loop antenna with reflector, very common. You could always try helical design too, more directional than the open loop but has more gain.

bloodhound31 · #5 13-09-2006, 09:17 PM

I have no idea what that means, but rest assured, my mission now will be to find out and have a play with it!!

Cheers,

Baz.

Doug · #6 13-09-2006, 09:25 PM

I agree with Andrew, a Helix antenna would be worth the extra effort over a simple open loop.

I have attempted to post a scan of some info on the helix antenna.
depending on the amount of room you have, these could be set up as an array of 4 helixes, but at 15M wavelength, you need a wide open area.
HTH,
Doug

bloodhound31 · #7 13-09-2006, 09:52 PM

Thanks Doug, it looks like it would be a good one to work on after I have finished playing with this one. I havent got a receiver yet, but as soon as I do, i want to see if what I have built with virtually no radio knowledge, can work.

The helix scan you sent me is a bit gobbledygook to me, because I am a radio numpty

at the moment. I am still working from photos and plain english. Wiring diagrams and schematics are still a mystery to me.

I do appreciate it though and will attempt to work it out mate!

Cheers,

Baz

Terry B · #8 13-09-2006, 09:58 PM

There is an interesting site about simple radio telescopes being used as interferometers. see http://intro.fringes.org/
It has it's origin on a simple interferometer that was built at the ATCA at Narrabri in 2001. ( http://www.narrabri.atnf.csiro.au/~bro764/YASI.html )
I saw it at the time. It was essentially a wire clothes line but it worked.
Take a look at the two sites for some ideas.

Terry B

bloodhound31 · #9 13-09-2006, 10:31 PM

Thanks Terry, will have a gander. Thanks to you all blokes, because of your timely and informative feedback, I have some good reading up to do. Looks like I better go down to revolve with ten bucks and see what scrap bits of wire etc, I can come home with.

ballaratdragons (Ken) · #10 14-09-2006, 01:30 AM

This site (link below) is a sample of some of the sites that turned me off building my own Radio Telescope!

Scroll down through the whole page and see why I was turned off the idea.

http://my.integritynet.com.au/purdic...-telescope.htm

bloodhound31 · #11 14-09-2006, 10:35 AM

OMG!

Yeah...It gets way too techo doesnt it? Some times when we create pages for the beginner, we forget that there are amateur zipperheads out there who havent the slightest idea of wiring diagrams, circutry and technical jargon.

Beginners are just that....BEGINNERS! They should sometimes be treated like 5 year olds...then they might actually learn something!

Just like me!

Terry B · #12 14-09-2006, 11:18 AM

Here is a link to radio Jove, a NASA sponserd kit radiotelescope.
http://radiojove.gsfc.nasa.gov/

Doug · #13 14-09-2006, 04:32 PM

Yeah, ageed, however most of the receiving gear can be purchased 'off the shelf' Especially the UHF equipment (definitely not for novice constructers).
Things like Helix antennas and/or stacked arrays are really not that complex to build.
The theory can be a bit involved, but who needs to understand the whichness of the why? I'm convinced that 99.9% of TV antenna installers are totally clueless about how the product they install works. But as long as they leave the 4:1 balun in their pockets, there is not too much to go wrong.
In the scan of helix antenna formulas that I posted just remember that the upside down 'Y' thingy (Lamda) represents the wavelength which is 300 divided by the frequency(in mhz)
Don't be discouraged by schematics they are mostly beyond all but the very best home constructors.
There are some specialised receivers for Radio Astronomy that plug into pc's but I have no links on hand, but can get them if I ask the right people.

Go with your 15M receiver and open loop and see if you want to progress.

best,
Doug

bloodhound31 · #14 14-09-2006, 09:59 PM

Good on ya Doug, thank you.

Will keep you posted as I progress.

Baz

JimmyH155 · #15 15-09-2006, 02:47 PM

I have got an ICOM R75 HF receiver and wonder if I could use that?? One thing I dont understand is what are you supposed to hear?? Just hissing noises or what? Half wave dipole looks easy enough, and putting it East - West no probs. Set receiver to 30MHz and listen to the Sun?? More really simple info would be great. I've also got a Uniden scanner which goes into the hundreds of MHz. Any good??

netwolf · #16 15-09-2006, 07:05 PM

This has always been something i wanted to do since studying at uni. What i was thinking was more along the lines of a phased array of antennas. By varying the phase of each element you can essentially point in diffrent directions without moving the antenna element. Coupled with PC based spectrum analyser, you could see a whole new world of stuff. I am not sure what in terms of technology is available out there second hand or off the shelf.

Doug · #17 15-09-2006, 08:26 PM

Jimmy I wouldn't like to seem like a wet blanket, and I have no idea where on this planet Burpengary is located however..............
Some things to consider: 10m (30mhz) is a noisy band subject to reflected radiations from the ionisphere (skip), and the ground wave at these frequencies run for about 160Km or so. Not a good look for radio astronomy and low gain antennas.
A half wave dipole is about as simple as you can get however it has a gain of about 1 ie unity gain. In the horizontal polarization orientation you are proposing it does tend to exibit a gain of sorts due to to the fact that errr ahhh well, maximum reception will tend to be more pronounced at some angle other than perpendicular or axial. It will have a feed impedence of 75ohms, is balanced with respect to ground (purely an academic point though).
Antennas in general: the lower the gain, the more omni directional or the less directional they are. There is another important consideration in choosing an antenna design and that is things like half power beam width, front to back ratio, & side rejection. Although these are inter-related the exact performance differs fron design to design.
What is needed for radio astronomy is a very high gain antenna or array of antennas. An area well away from sources of man made interference. At HF frequencies stearable arrays take up a fair bit of realestate
Right, so now that I have turned you off the whole idea

, here is an attempt to redeem the situation::

If your scanner is a good one and can tune up to around 1.4Ghz the 21cm band you could play around with some really nice hi gain arrays that would have sufficient directivity to enable you to say that what you are hearing is where your array is pointing, and not something just over the hill.
And unless you tune into ET, static is all you will hear anyway. That is why you need 'HIGH GAIN' because it is the static that peaks when you point to a radio galaxy that tells you are hearing a radio galaxy. but with an omni directional dipole you are not really pointing anywhere, or more to the point you are pointing everywhere.
If you really wanted to do something with your recieved signals you would need to be able to record and graphically display them.

BTW it was winradio that I couldn't think of in an earlier post, so now it has been named in another thread.

sorry if this seems to be a discouragement, but I think you have a right to know what you would be up against.

cheers,
Doug

netwolf · #18 16-09-2006, 02:02 PM

The frigne link is very good one, it seems like by using two antennas they are trying to do what an Dif AMP does to cancel common noise. Because both signals arive with the noise out of phase they cancel each other out.

Regards.

74tuc · #19 25-09-2006, 09:03 PM

Hi Barry,

Don't know much about radio astronomy but I know a bit about radio communications. I like your project and wish you all success. A steerable antenna for 21.9MHz. is quite "doable". The easiest and most manageable antenna would be two 4 element yagi antennas suitably phased. Each antenna would be about 6M long and approx. 7M wide maximum. Because the antenna will have its back to the ground the antenna should have the maximum front to back ratio. Mechanically this twin antenna will be very nice to balance. The antenna needs to be steered in one axis only and this may be done by hand. The rotation is in the plane of the eclliptic. One thing that may need to be considered is the polarisation of the antenna. You may consider using a circularly polarised antenna as you will be receiving signals from space and the source (Jupiter) is rotating - selectable (RH or LH) circular polarisation would be a nice feature.

I do not know how strong the Jupiter signals would be but a low noise front end amplifier would be in order. This amplifier will determine the performance of your receive system so it should be the best you can afford.

I do not know the bandwidth of these signals so I would use a single sideband (SSB) receiver - commonly available - and using the USB mode take the audio output and sample the audio with a sound card and have a look at the "Jupiter signal" with a program like "Cool Edit".

Thats my worth. Good luck with the project.

Clear(low noise!!) Skies,

Jerry.

74tuc · #20 25-09-2006, 09:14 PM

Sorry!

What I meant to say in closing was "Thats my 2 bobs worth".

Jerry.