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About pasaphil

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    Norfolk UK
  1. I'm using a cheap domestic Optima Octagon but these modern units use a cheap Xtal and PLL to generate the Local Oscillator so can be locked by pulling the Xtal and injecting the Xtal frequency into multiple units. Phil
  2. That was what I had in mind but i was going to just coil it so I learned something today as I'm more used to keeping everything small and typically 10cm for RF cables. Local oscillators are going to be phase locked as the PLL type LNB's use a standard Xtal so I will run a separate 27Mhz feed to each LNB from a common source, remove the Xtal's and tune the lengths in the same way but at 27Mhz it's not too hard. Phil
  3. I am going to try my hand at aperture synthesis but with the telescopes cabled together so it's just a timing delay issue rather than the bigger problem of synchronisation issue on different sites to start. There are open source correlators out there and a 3 node scope is pretty low tech for serious radio astronomers (hi tech for me at the moment). Got the double oven OCXO + DDS running and sync'd so will give it a go in the new year. Might even make a video and stick it on youtube for people as nerdy as me ?
  4. Hi, All interesting things for me to try. I did start with drift scans of the sun and just wanted to get more data faster and could never be sure exactly where the dish was pointing so I wanted it much more precise so I could try some interferometry. The pointing accuracy is 0.05deg but the dish beam width is closer to 2-3 degrees so I I'm currently tinkering with locking two PLL LNB's together and syncing to the GPS 1PPS time signal and having two dishes 50m apart (best I can manage here) and possibly one in a different location but I need to sync them to 250ps so not impossible but challenging as the raw 1PPS is +/- 10ns Phil
  5. There are lots of solar observatories out there and radio emissions are in many ways far more interesting than the visual disk. Probably not the best time to image the sun coming into a grand solar minimum but you should be able to image the sunspots and flares etc and track and log emissions. Moon is a lot weaker signal but should still be fine with a larger dish fitted. Most of the things NASA is looking at will not register at all on a small dish so you have to look at what is possible for the amateur and the solar system is workable.
  6. A 70cm dish has quite a wide beam so it will be interesting to see how this changes when i get two of these sync'd up 30 meters apart (I have 3 of them) Phil
  7. Using the geostationary satellites is good for alignment but as you say not particularly useful beyond that (nothing worth watching is ever broadcast). The idea really was to build a steerable mount with controller that I could attach either a dish or yagi and sync up a few of these to make an interferometer which is why I went for a high pointing accuracy. The telescope part is quite open once the mount works well. I still have to add the sidereal tracking code for solar and lunar observations but this should not be too hard and I have already done a few test solar runs and it works well. Dish size is going to be the limiting factor for many things but the mount should handle a 1.8M dish so it's not quite a lovell but should generate some interesting data. Also it should be good for tracking the non geostationary satellites as it can slew nice and fast. Phil
  8. Hi, It shows the signal strength at the 10Ghz band used by Satellite TV transmissions and is a raster scan of the sky at 0.05deg per pixel. Phil
  9. Hi, The LNB output is fed to a log detector and then a 12bit ADC. I then take the high 8 bits and use them as an offset into a colour map which is a 256 pixel wide bitmap. The colormaps are used in various software and can be downloaded as small bitmaps. The one I used was called inferno. Then I read the pixel at the offset address and added it to a bitmap at the x,y position to get the nice coloured image. The original 12bit data I stored as a DICOM image to retain the resolution. Phil
  10. Hi, I have been working on a home built radio telescope for a while and currently still working on the mount and tracking so no ground breaking stuff yet. I have however been imaging the Clarke belt to optimize the tracking so thought I would upload a couple of images that I have been able to scan. These are using a 70cm dish and a standard LNB and an Alt Azimuth mount with home made controller and the zoomed image is of the UK sky TV satellite. Hope some of you find this interesting. Phil
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