1. Jul 19, 2016

### jamalkoiyess

Hello PF,
I was wondering if there is any good guide to build a radio telescope that can give me an image not just a graph. I am just a starter so any advice or tips are relly appreciated.

2. Jul 19, 2016

### davenn

an image is build up from lots of graph data sets
go for the graph style for a start, that is going to keep you extremely busy and poor building it

3. Jul 19, 2016

### davenn

firstly you need to decide

1) budget
2) what specific object(s) you want to observe ... different ones have different frequencies
3) depending on the answer to #2, that will determine if you will need a dish and low noise amplifiers
or a wire antenna or maybe Yagi antenna(s)

Eg
atmospheric whistlers can be received on 10 - 20 kHz (ELF - VLF)
solar flares from the sun can be received from around 1MHz to 50 MHz (HF to VHF)
Jupiter noise on around 18 - 24 MHz ( HF)

any deep space objects are going to require lots of ground space for BIG antennas and decent money for

Dave

4. Jul 19, 2016

I am new to this field so my budget is not more than 200$. I will not take more risk for something i don't know. For the objects i would go for solar flares and the jupiter noise ... sounds more interesting. So any good setup ? 5. Jul 19, 2016 ### davenn OK$200 is going to be a little difficult but not impossible

a "shortwave" HF ( high frequency) receiver that covers say 1MHz to 30MHz .... shop around
you may find something second hand for $200 that has respectable receive an old Yaesu FRG7000, a bit pricier a FRG7700 or a Kenwood R1000 all three of these are 20++ yrs old you wont get anything better unless you are willing to spend lots more you will still need to get an either an old pen chart recorder and lots of paper or a digitiser ( datalogger) for a computer eg a picoscope logger https://www.picotech.com/products/data-logger this is just one brand, there are many others out there, they all come with the driver software for displaying the signal then you need to get wire etc for making an antenna ... that's almost the cheapest part you are probably not going to get much change out of$500 - 700

.

Dave

6. Jul 19, 2016

### jamalkoiyess

But do i need a dish or an antenna ?
I am building it on my own so if you could help me and list the parts that would be a huge thanks for you.

7. Jul 19, 2016

### davenn

for the sun, earth atmospherics or Jupiter, just a wire antenna
sun and Jupiter a dipole antenna tuned to around 20 MHz
for earth atmospherics a large multi-turn loop antenna

you should be seeking out the help of a local amateur (ham) radio operator for some hands on mentoring and guidance

Last edited: Jul 19, 2016
8. Jul 19, 2016

### Chronos

9. Jul 20, 2016

### jamalkoiyess

Yeah i can get help from a friend in my area who has a masters in electronic physics and works as an electrician so he has the experience.

10. Jul 20, 2016

### jamalkoiyess

11. Jul 20, 2016

### davenn

don't be confused
the wire dipole and or yagi antennas are for HF and VHF ..... 1 MHz - 30 MHz ( HF), (30 - 300MHz VHF)

dish antennas are for low band to high band microwave frequencies 1 GHz and up

for you at this time for the least money outlay you need to do as I suggested back in posts # 5 and #7

THEN ONCE you have mastered some of the basics, and started recording signals and still have the interest, then you can start looking at reception in the microwave bands

basically .... learn to crawl before you learn to walk or run
As you move higher and higher in frequency, things get more difficult and more care needs to be taken in construction etc

Dave

Last edited: Jul 20, 2016
12. Jul 21, 2016

### diogenesNY

Just for fun, check out this website:

Lots of radio related surplus and unusual parts.... Lots of once very costly and amazingly overengeneered military surplus radio and antenna gear. Never know what you are going to find, and HF range stuff is often in abundance. No affiliation, just occasional customer. YMMV.

Funky retail shop in Lima, OH as well. A fun visit if in the neighborhood.

diogenesNY

13. Jul 22, 2016

### sophiecentaur

You need to take into account that the resolution (beam width) of an antenna is related to how wide it is (the aperture). A dish antenna has a well defined aperture as long as it is several wavelengths in diameter. The effective aperture of a Yagi antenna is fairly small and it is normal to just plot a rough pattern or use manufacturer's figures for the sensitivity pattern (so called Radiation Pattern). You can get much better directivity for shorter wavelength signals. If you are receiving (round figures, here) signals with a frequency of 3GHz, the wavelength is 1cm and the beam width of a 1m dish would be round about 0.5° if everything is done right. That would give a pretty glubby image and would not separate distinct sources which are closer together than 0.5°. A yagi antenna, looking at a VHF signal, would have a beam width of more like 20 or 30° Plotting a graph of signal level as you sweep the antenna is the best you can hope for until you have assembled a sophisticated system to produce 2D 'images'. There is no equivalent of a photo sensor array as in an optical telescope, to give you 'pictures' directly of the RF signals arriving on Earth.
For radioastronomy imaging, it is necessary to find 'quiet' frequency bands where there few man-made signals because it is very hard to reject them using the directivity of any array that you are likely to be able to afford. You have to pitch your expectations at a realistic level but it would be pretty rewarding to identify a source of RF signals in space. There are other things you can do with signals from space. This link describes the reception of reflected VHF transmissions by a meteor shower - no particular directivity is needed for this and the picture shows a fairly low gain yagi antenna.
I agree with Dave about looking for surplus equipment. You do, of course, need some DIY ability with RF electronics if you want to get cheap elderly stuff operating properly. A good learning process, though.