Poor Man's Radio Telescope

A way to peer into the radiosky using little more then junk found on the side of the road.

Remembering back to my 10th birthday. I recall receiving a book on outer space. I believe it was published by National Geographic. This was by far my most prized book in my somewhat limited collection of the time.

In it there was a rough outline of a radio telescope. This diagram so intrigued me that for years in the back of my mind I dreamed of being able to play with one.

Indeed years have past, careers, children, and everyday life was by far the most important of responsibilities. Then it happened. I spotted a 10 foot satellite dish in someone's trash.. I quickly made off with it and all its components.

The mount was in pretty bad shape. It appears to have some serious wind damage, and the pedals of the dish are in less then what I would consider acceptable shape.

None the less I slapped it all together. In the picture you can see my stinky trashcan mount. It was good for a quick test but boy did it stink.

Step 1: An examination of the feed assembly

Here we see the feed horn and low noise amplifier. All the dish components were hauled to the curb except the actual receiver unit. The bolts holding the wave guide and the amp onto the feed horn had to be purchased. Getting this feed horn back into working order took a little bit of time. It seems that the feed horn assembly was home to a community of wasps. I never realized this before but wasps build there nests to last. It took a good bit of probing and a little 409 to clean it up nice.

This is basically the meat of the system. It takes the focused energy of the dish and downconverts it into a usable signal and then amplifys it.

How is all this powered you might ask? The voltage actually travels down the coax cable that is delivering the signal to the next stage.

The polorizing servo is basically left alone, but for those of you that are curious it's a little motor that turns the antenna inside the feedhorn for better reception.

Comments

[TechPaul]

ahhhh yes, my RTL dongle is attached to a Raspberry Pi

[TechPaul]

easy 1420mhz receiver, a RTL dongle with the R820T chipset. Mount it at the feedhorn. No coax neede just shielded Cat5. Yes they do drift a bit but it is cheap and you can always add a Roman Black crystal heater.

[myamiphil]

http://www.gb.nrao.edu/epo/ambassadors/ibtmanualshort.pdf

[jiripolivka]

I have made similar radio telescopes using satellite TV LNBs, at 4 GHz (C-band) and at 11 GHz (Ku-band). All work well.
I am confused to read that your C-band radio telescope was sensitive to cloud cover. It should not be, clouds and rain affect only Ku-band.
Using the Sat Finder is possible but as this device is designed to indicate satellite signals, solar noise response is quite non-linear with the knob setting. I prefer in my designs adding an inline IF amplifier ($4 at MCM Electronics), and I make a detector followed by an opamp, to adjust zero and gain for an analog indicator.
In addition to solar-noise demonstrations, such simple radio telescopes are interesting remote sensors. One can indicate his/her body temperature, emission of microwaves by walls, vegetation, clouds/rain and fluorescent tubes.

[revelation]

CAN A Dish be used to make a Death Star type weapon to blow up stuff ?

[ilpug]

I did a spit-take on my keyboard when I saw that you labeled the dog crap.

Just shows my maturity level tonight.

Anyway, great idea. I have no idea of the electronics involved, but if you ever get some coherent images, i would love to see them.

[wanna be macgyver]

Hi zOrb,

Thankyou for uploading this project. My father-in-law installs dishes and decoders. He's going to love doing this project with me.

Thankyous to the people who have added comments for this project


Regards

[HisDivineShadow]

is there a way to conect this to s screen to see the shapes of the radio transmitations of extra terrestrial phenomena?
Ouch
...to see the shapes of radio tranmission of other worldly objects....

[muunkky]

You can use this setup for more than seeing the sun. Just plug the raw feed into an oscilloscope and jack up the 21cm bandwidth and you've basically got yourself a high powered radio telescope. Not sure how the LNB is affecting your signal, might want to take that off to get raw analogue goodness.

[z0rb]

It would be great if I had a scope that could go up to 21cm :)

[muunkky]

Haha, good point. An analogue UHF video receiver should do the trick though.

[z0rb]

Sounds like butchering an old TV might do teh trick.

[muunkky]

It depends on the Low Noise Downconverter (LNB) on the dish. The raw feed from the 21 cm line (1420 MHz) will be downconverted to probably around 1400 kHz which could be picked up on an AM radio I believe, but you need to check the specs.
It may block everything below 4 GHz which means you'll never see the 21 cm bandwidth (*sob*). If this is the case and you really want that hydrogen line, you're better off removing the LNB and installing your own feedhorn, band-pass, and low noise amplifier and downconverter for the 21 cm.
You can get all these parts at http://www.radioastronomysupplies.com/radio_astronomy_supplies.php

[Chwlo]

z0rb can you take several dish network dishes and align them to make a more powerful and or longer range radio sat. If so can you point me in the right direction for this project. I can get plenty of them for nothing. I thought if I could space them out say over a hundred sq yards and align them I could pick up much more distant noise. Yes no hmmm.

[z0rb]

Sounds to me like you are talking about an inferometer. The concept is possible since this is how most klarger radio observatories work, however I am not sure where to get the equipment to effectivly phase all these dishes together. Below are a few links for further reading. Also you might want to post this question in a a forum with people in the know :)

Good luck.

http://www.radio-astronomy.org/

http://www.umich.edu/~lowbrows/reflections/2007/jabshier.1.html

[SolamenteDoug]

My science project through most of high school involved a homemade radio telescope. It was a 2-meter helical antenna with a modified police scanner, amp and multimeter. It was sensitive enough to pick up the Sun and Jupiter as well. It was less a scientific instrument and more an experiment itself. I'd like to get back into scope making when I get a yard. Keep up the good work!

[thepelton]

It would be interesting to map the sky, and find out where the "hottest" parts are. I suspect that the center of the galaxy would probably put out more radio waves that other places.

[z0rb]

From what I hear Taurus A is pretty loud in the radio spectrum. Unfortunately I am not in a neighborhood anymore that would tolerate such construction in my back yard :)

[thepelton]

Jupiter I heard is also quite noisy.

[z0rb]

Indeed it is, but Jupiter it loudest in the decametric wavelengths 18-24 Mhz. That requires a slightly different atenna. You can find more about that here

http://radiojove.gsfc.nasa.gov/

It's fairly inexpensive to get a setup going.

If you are interested in some other solar monitoring I have been doing you can view that here

http://z0rb.livejournal.com/2008/04/13/

Enjoy

[rod_sutter]

I need a little help, im building a lbt can you give me more detail instruction on how to power the satellite finder with the 12 volt converter, and how can I hook up my laptop to the satellite finder to record the signals that come from the object were looking at.

[z0rb]

Well both the satellite finder and the LNB (Low Noise Block) are powered from the same source.

The satellite finder looks for a voltage (typically between 12-18 volts) coming in the receiver side of the meter. The link below spells it out a little. You apply the positive side of the voltage to the center connector and the negative voltage to the connector’s jacket. The little coily thing near the positive terminal of the voltage source is a coil of wire to stop the RF (Radio Frequency) from getting into the power supply. Pretty much any RF choke will do. My question to you is. What kind of power supply are you using? What kind of satellite meter are you using? It would also help to know what kind of dish and feed horn you are using.

http://i219.photobucket.com/albums/cc216/MightyZ0rb/meter.jpg

This is a little more difficult. It also depends on what type of satellite meter you have. If it is like the one above, then there are two possible routes you can take.

The first involves opening the meter up and fastening leads to the wires that go to the actual meter portion of the sat finder. These leads would then be hooked up to a data logging voltmeter. I use a radio shack one found at the link below.

http://www.radioshack.com/product/index.jsp?productId=2103962

The second method is not nearly as accurate but it would be a cheap way to get started. The particular satellite finder above has a little piezo element that chirps when a satellite is found. The knob on the front of the meter can vary the intensity of this. If you were to use a spectral analysis program. Found here (it’s free)

http://www.qsl.net/padan/spectran.html

And tape your PC’s microphone to the back of the meter it will show you when you detect something.

This is just my 10,000 foot view of your situation. Without knowing exactly the components your working with it’s difficult to advise the best way to approach this.

However I hope this helps, and if you wish to pick my brain further, shoot me an email via my website.

[Xellers]

If I don't have a satellite dish, and all I want to do is "see the sun", then how would I be able to build an antenna? Would I be able to make one? Please help.

[z0rb]

There are a variety of ways to do this. I would imagine that this will be dependant on what you have available and how you want to see the sun. Pretty much any radio receiver will be able to "see the sun" th etrick is to know what you are receiving and how to receive it. What equipment do you have at your disposal, and are you wanting to track the sun as it goes across the sky or have an antenna just pick up the sun and not follow it. Let me know and I'll fill you in on what I know.

[Xellers]

I just found a small dish today; only a few feet in diameter.
All I want to do is to be able to point it at something like the sun, and to be able to detect that.
The dish had a coaxial cable connection.
I am looking at using this: http://www.satpro.tv/index.asp?PageAction=VIEWPROD&ProdID=192
to interpret the signal.
It would be easy for me to construct the power supply that you described, so all that I need to know is how I should connect everything. From the explanations within your instructable, I was unable to figure that out.

Please help.
TY :-)

[z0rb]

The sat meter that you have is nice. IT should work just fine. The more stable the power supply the better. Basically the center conductor of the coax will carry your +12-18 volts. That goes on the side of the meter that is designed for the receiver. The other side merely gets hooked up to the feedhorn of the dish. The small dishes work on the Ku band which is up around 12Ghz. The bigger C band dishes work on 4Ghz. For you meter it does not matter since the feedhorn in either case will down convert the signals from 950-1450 Mhz Hope this helps.

[Xellers]

So basically, I should set it up like this:

[Xellers]

And by "outside of cable", I mean the channel that comes out as a ring on the coaxial cable.

[z0rb]

The looks correct to me

[maker12]

"I SAW THE SUN" the telscope is singing that LoL

[SHIFT!]

Hey Hey Hey! It's Krusty The Klown!

[maker12]

it is LOL

[gamma_fear]

I was looking at this and a thought popped into my head (finally!). i have a couple of satellite dishes on my roof if i replaced the built in receiver with a usb WiFi device with a usb extension cord (bad WiFi reception from my house) and some really cool servos to change its direction, would the dish reflect WiFi signals or would i have to add some sort of mesh?

[MattTheGeek]

would a dish network work for this project or do i need a bigger satellite dish?

[z0rb]

For something like the sun you really don't even need a dish at all, but it does help. A dish network dish will work just fine. In fact it's one of the projects currently on my workbench. Just remember the difference between the dish in this instructable and a dish network device is the band being used. The big dish runs on C Band which is around 4Ghz and a dish network device runs on Ku band which is 12Ghz. In respect to the sun there really isn't much difference between the two.

Here is a link to a great document on using a dish network dish.
Little Bitty Telescope

Enjoy and have fun

[HamO]

Great start... What are your plans for a receiver, what frequencies are you interested in? Keep us posted. Thanks for sharing.

[z0rb]

Well, this project was actually done a few years ago. Since then I have moved to another location. Currently I am workin gon a version of the Itty Bitty Radio Telescope. This is in the rfequency range of 12Ghz. as far as I know ther ear eonly a few things i nthe sky around that band. As for a receiver I have a few ideas I am still kicking around.