Last weekend I obtained the dish on ebay - C-band mesh for satellite reception, for $160 (just a 2.3m dish, no electronics.. still a good buy because it is easy to assemble the contraption in a backyard).
Then I stumbled on this website: http://www.haystack.mit.edu/edu/unde...srt/index.html
This is almost exactly what I had in mind.. I am not the first one here ;-)
Currently I am still building the LNA and BPF filter
For the receiver and recorder I will use SDR# and SkyPipe.. I tried it in a dry run, and it works OK (RAW signal, my audio card passes DC signal to recorder it seems..)
Anyway, I am hoping to at least detect the 21cm line, and it seems it will be possible to even do some Doppler measurements (I have high stability frequency reference, so it won't be hard to calibrate the TV stick properly).
Today I simply couldn't resist to preliminary assemble the dish..
First, I thought I will be able to mount it on EQ6.. but it's too cumbersome and too heavy (13kg of what's on the image below, plus I would need a counterweight.. too much).
Feeder is made from one of my wife's unused pots (7" dia, 3" deep - ideal!)
Antenna is helix, 2 turns of 4mm wide copper tape, wound and glued on 68mm dia pharmacy box (krill oil, I think.. on the image near connector (SMA) you can see the matching section, 22mm 75ohm cable plus 4nH of wires - measured return loss is >10dB at 1420MHz).
All in all, getting there...
EDIT: after playing with RFSim99 a bit, I (theoretically) managed to improve the matching (pic attached). It's much more broadband with additional 75-ohm shorted lamda/4 section in parallel to connector.
Now, seriously, there are many things that can be done with this receiver.
Sun observation is only one little thing.. galactic plane observations is what I wish to do. And Magellanic clouds detection.
It is also pure technical challenge!
Oh, come on now, we all know you just want to hack into everyone's WiFi from the comfort of home! Say, you don't happen to live close to a foreign embassy by any chance ....
Seriously, though, that is really cool. I used to have an old MW/SW radio as a kid and tune into various terrestrial signals. I always wondered if it'd be possible for an amateur to do the same with signals from space.
...I always wondered if it'd be possible for an amateur to do the same with signals from space.
I am looking forward to that myself.. I am pretty sure it will not be too hard (especially to detect Sun activity).
As I mentioned earlier, this time around I will start with single atom Hydrogen line.. maybe later, if I don't loose interest in the meantime, I will try with OH (18cm) maser emissions...
Quote:
Originally Posted by icytailmark
you must get free foxtel
That was the official justification for SWMBO, as alternative - if the primary project fails
Hey bojan!..............if you pick up the sound of mechanical grinding and thumping at regular set intervals, send me a P.M. and I'll give you Jodie Foster's phone number!
I am most impressed mate..........keep us informed!
last Tuesday, I tried the antenna on Sun, but no joy..
After I checked the whole thing once again (cables, matching, feeder.. everything seemed to be in order) the conclusion is: 1.4GHz signal from Sun is still below the noise floor of the receiver (Elonics tuner, <4dB NF).
Well, since the company I currently work for as contractor decided to offer me an extension, I decided to celebrate this happy event with preamplifier from Minicircuits . It will arrive on Friday, so weekend wil be busy again (I hope.. in principle, I could easily do it through the clouds, provided I had setting circles on the antenna, which I don't.. yet.)
Join the club. I had a dish that had a beam width (3db) of 10 degrees and a gain of 24db.
A 30db low noise preamp and a HP spectrum analyzer with a noise floor of -117 dbm. I could not see anything from the sun with this set up.
I had no bother with the 3rd harmonic (1427Mhz) of a little hand held CB radio at about 50 metres. (Did not test at any greater range). I would have thought this was enough to see the sun but apparently it is not. I have not done anything since as the mechanical work became too heavy for me.
Hi Barry,
Yes, it is curious.. because according to this website, it should be easy(er).
Well, my antenna has 28.7dB at this wavelength (2.3 metres dia), so 20dB amp (at 0.5dB NF) should be a bit better than what you had at hand...
I will keep you posted..
Update:
After unsuccessful attempt at Sun with just antenna and SDR (and spectrum analyser), I purchased LNA from Mini Kits, 20dB gain.
Also,I made interdigital hairpin filter some time ago, the PCB arrived yesterday.
After some adjustment, I obtained 8Mz BW (3dB), 1dB ripple... pretty good.
However, the insertion loss is quite high, 10dB.. so this filter can be used, but after LNA. And there will have to be another line amplifier.. 16dB or so.
In the meantime, I started building the "proper" interdigital filter, I expect much lower losses with this version (<0.5dB? hopefully..)
Anyway.. getting there, but somewhat slowly..
The saga continues..
Update:
LNA and line amplifier (36dB total gain) are mounted, ready for test.
I just need a clear sky, so I can aim the antenna at Sun (I still do not have motors for positioning and tracking (one day, Sound Stepper System will take care of that, but first I need to detect something, before I go any further))
Unfortunately, the filter, as it is now, could not be tuned on 1.42GHz, because the resonators are a bit too long (1mm.. currently, it is tuned ~25MHz lower, and I am still waiting for SMA connectors from ebay).
After some time, I am back to the project :-)
Filter is tuned on the frequency, but I am still not happy with response - it is not flat (ripple is +/-1.5dB, and the attenuation is 3.5dB.. too much for placing this filter in front of the LNA.. so it will have to go after.
Getting there..
Now you just need to mount the dish on an EQ6 for tracking the Sun.....
Hi Matt,
I was contemplating this.. but it is too heavy for EQ6 (actually there are two counterweights required - one to balance the dish + feeder on DEC axle, and then another one to balance the whole thing around RA axle .. 60-100kg or more it total.).
At the end, I will be using alt-azimuthal mount, with Bartels or SoundStepper software to control it.
!
