Low Budget Radio Telescope
ajward
Posts: 1,130
I finally scored a surplus 30 inch satellite antenna to experiment with radio astronomy. The dish frequency range is 2 through 1215 MHz. Power to the LNB is provided by a 21 volt "Power Inserter". Signals are detected by a Channel Master 1004IFD Satellite Signal Meter.
It's set up here aligned on the Sun while I try to determine the antenna beam width. I'm using the 1004IFD to measure the time it takes the Sun to pass through the antenna's field of view.
Tonight I'll calibrate the meter to a "cold area" in the night sky. That will allow me to make some kind of meaningful observations.
Though somewhat limited by the frequency range, it's possible to measure fluctuations in Solar radiation, changes in the surface temperature of the Moon, detect human body heat (Tho' I don't know at what sort of range) and... oh, detect satellites! :-) I've read it's possible to detect radio emissions from Jupiter, but as difficult as it was figuring out how to align on the Sun at first, finding Jupiter should be a ball!
Things to be added: an interface to convert the FM signal to AM for software analysis, some sort of motor drive for Az and El (although drift scans of the sky can be interesting) and a couple of flashing LEDs on the perimeter of the dish (just for giggles).
Anyone done anything like this? Love to hear about your experiences.
Anyway... that's the latest shiny thing... among many! :-)
Amanda
It's set up here aligned on the Sun while I try to determine the antenna beam width. I'm using the 1004IFD to measure the time it takes the Sun to pass through the antenna's field of view.
Tonight I'll calibrate the meter to a "cold area" in the night sky. That will allow me to make some kind of meaningful observations.
Though somewhat limited by the frequency range, it's possible to measure fluctuations in Solar radiation, changes in the surface temperature of the Moon, detect human body heat (Tho' I don't know at what sort of range) and... oh, detect satellites! :-) I've read it's possible to detect radio emissions from Jupiter, but as difficult as it was figuring out how to align on the Sun at first, finding Jupiter should be a ball!
Things to be added: an interface to convert the FM signal to AM for software analysis, some sort of motor drive for Az and El (although drift scans of the sky can be interesting) and a couple of flashing LEDs on the perimeter of the dish (just for giggles).
Anyone done anything like this? Love to hear about your experiences.
Anyway... that's the latest shiny thing... among many! :-)
Amanda
1024 x 612 - 108K
Comments
As I understand it, the high end of the frequency range of a dish depends upon the spacing of the grid elements that make up the dish - the spacing should be at most 1/10 the wavelength. In the case of a solid dish, this does not apply.
The low end of the frequency range depends upon the aperture. The aperture should be something like five times the wavelength.
I would think that your dish would have been used somewhere in the 12GHz range if it was for satellite TV.
Your dish should work well for 2GHz and up.
I have been told, emphatically, that I am wrong about this so if there is disagreement please feel free to set me straight.
Heh... Not the greatest setup, but when working from the second floor observator... er, second floor balcony, ya gotta go with what works. :-)
Monitoring Jupiter would be a long-shot, but down the road, adding equipment... who knows?
So far I've gotten some good signals from Sol. The signal meter peaks if I walk in front of the dish. If I slew the dish across the neighborhood, I get a couple of signal peaks from thermal hotspots.
Fun? Oh heck yeah!
Now to work some Parallax products into the game!
Amanda
Are there propeller plans in your radio astronomy future?
IF you want some Good places to get some stable sigs Look at AMSAT Ham sats in orbit.. they are in the 144MHZ band up to 10 GHz so there are quite a few your could use as "" RF markers "
Peter...
In my research, I failed to note the listed frequency was for the dish/LNB output. DOH! Specs for the dish indicate use in the Ku/Ka bands, 12 - 18 GHz and 26.5 - 40 GHz respectively. I suspect it will function in the gap (K band), but I can't reference that since its intended use was for teevee. :-)
@
For the moment, it's just connected to the Channel Master signal meter. Still finding the best way to aim the dish and the audio indication is all I need.
@
Actually one source I found used a BS2 Homework Board as part of his data logging setup so I'm sure the Propeller would be well suited for such service!
@
Identifying them will be a little harder. The altitude scale isn't too bad, but the azimuth is the pits, allowing only a few degrees of movement and no indication of direction.
Amanda
@Humanoido - I've worked out a way to set the azimuth. Again a low end approach 'cuz I really don't super precision aiming at this time. I'll post a picture when it's completed and mounted.
Amanda
Edit....
I attached my rough azimuth scale to the support pole. A piece of expanded PVC foam connected to aluminum angle then clamped to the support. Scribed azimuth lines on the foam at 15 degree intervals (close enough for now). Also scribed a line on the locking collar. I was going to trim the foam in a circle for appearances, but two things changed my mind: a) The extra space gives me a place for small notes and b) But most importantly... laziness!
I aligned the antenna on a known satellite (I think so anyhow) then set the scale so it was on that reading. Fingers crossed!
Today's experiment is to try to aim the dish where the sun will be at a certain time, in this case 11:45 AM. If everything works, the signal meter should start detecting the sun at about 11:35, peak at 11:45 and fall off again at 11:55. Funsies!
Edit 2 - The experiment worked... mostly. The elevation was slightly off and the signal was a little weak, BUT the alignment wasn't bad. The signal curve fit pretty well within the times I'd expected.
Amanda
In the meantime, I'm using a multimeter with RS232 connected to the signal meter circuit and the output goes to a data logging program on my netbook.
Above, the left part of the trace just shows some antenna movement. To the right, the antenna was locked in place and the Sun was starting to enter the FOV of the dish.
The chart displays the results of a 2hr 50 min scan. The object was to try to detect detect radiation from the galactic plane. I'm not really sure what I'm seeing tho'. My azimuth scale was knocked out of alignment by a cable guy earlier in the week. <grrr>
Also I had to cut the scan short, dark clouds were coming in and I didn't wan't to get all the equipment soaked.
Amanda
Amanda, you may want to take a look at telecope Go To hardware for aiming.
See http://en.wikipedia.org/wiki/GoTo_(telescopes)
lol
It might work like a static load anyway, SWR so bad at 2mhz, the blurred magnetic lines of flux create a glowing halo of refracted RF that works like a 50 ohm dummy load..;0)
I once inherited an old wire mesh C-band antenna complete with dual LNA's and X/Y rotators...back in 1997 when I rented a house from a good friends mother.
It also had several nondescript and thus probably ancient receivers and mysterious tuner type devices that I estimated to be the earliest forms of satellite TV lock-out coding methods.
All I messed around with using it was evesdropping on signals I found scanning up and down the crude receivers freq range, knowing where I was tuning at by tapping into a mixer VCO with a frequency counter...and then, I am not totally sure I knew exactly what I was tuned to even then...
They still have that radio-science-mysteries-from-space appeal if you ask me..
Ya... but the dish is tuned for the 12 - 40 GHz freqs. Typically used for teevee reception although, I'm not sure what goes on in the K band. Anyhow, the whole thing is just an experiment to occupy my retired years! ;-) (And I'm sure the building manager would have fits if I started digging out a hole for a radio telescope beside the building.)
I'd love to have to have a motorized mount to track objects. But $$$$$$$!
Amanda
I have one of those, but it's designed for a 60mm refractor. However, I might be able to use the 'scope to get az/alt coordinates and transfer those to the dish aiming setup!
Amanda
Not if you find a few stepper motors or even a couple linear actuators from a somewhat big RC aircraft....then you can homebrew something pretty quick and very cheap!
I look forward to seeing how your experiments turn out!
In LA, would the neighbors even notice?? :0) the same but opposite from my situation. Our neighbors are so far away, they couldn't even pick me out of a police line up....um, just a hypothetical, there.
Astronomy is my second favorite "shiny thing"! I have 5 telescopes... a 60mm refractor on an alt/az mount, a 60mm refractor on a goto mount, a 76mm reflector on an eq mount, a 102mm refractor on a goto mount and a 127mm reflector on an eq mount. The first coolest thing was seeing Jupiter, the bands and four of his moons and the second was seeing Saturn and making out the rings (not real well, but seeing them nonetheless!!!!!).
I understand other folks lack of exuberance... I had my roommate come out to look at Jupiter and her reaction was kind of like... "okay". :-(
Amanda
The data indicates peak signal at about 11:59AM. Pretty darned close to the predicted 12:02 considering the rough aiming used!
Amanda
Edit: I've found that temperature effects the signal meter. (I've always set up everything on the balcony, so I'm adding coax cable to bring everything except the dish and LNB inside.)
That's very cool. What size receiver "beam" does that translate into, do you suppose? Maybe 3 degrees or so?
When I first started experimenting with the dish, I came up with a field of view of about 5.5 degrees... not sure that's correct. It's an oval antenna... about 18 inches high and 30 inches wide.
Amanda
If you aren't familiar with it, calsky.com is the "calculated sky", an online astronomical calculator. Up at the top, select the object you're interested in. In this case, click on the Sun, then click on Ephemeris. You'll see rise, set, and transit times in that short list. For Jupiter, click on Planets, Jupiter, then Positional Ephemeris to get the transit time. Make sure you've entered your location so the code calculates the correct times. While I'm sure you know, Amanda, for those unfamiliar, "transit" in an astronomical sense means passing through the local meridian.
Hope that helps.
Bob
[Edit]: PS, next time show your roommate Saturn instead. That usually gets their attention.
The upcoming goal it to try to detect emissions from the galactic plane which should be passing through my FOV tomorrow afternoon in a near vertical orientation. Hopefully that will register as a small peak in the readings.
Amanda
For more fun, why not try spotting Jupiter during the day? http://www.space.com/20629-see-jupiter-daylight-sky.html