A nice sunny day with no wind today – ideal to set the dish up outdoors and see if my simple and very cheap setup can detect signals from the Es’hail 2 OSCAR-100 package.
The answer is – yes!
So here’s the story. The dish is a 60cm satellite dish, bought years ago with cheap LNB and receiver in a B and Q sale. Last year I started putting it on a motorised drive, which will in due course be computer controlled so that I can track deep space stuff. It’s not automated yet, but the motorised steering means it’s easier to find geostationary satellites like Es’hail 2.
I was of course using the PLL Octagon LNB as its frequency accuracy is greatly superior to the old DRO LO version that came with the dish. However it is set vertically on the dish, not adjusted for polarization offset. (It does mean I should be able to receive something of both vertical and horizontally polarised signals!)
Initially I couldn’t find the Es’hail 2 satellite, so I went back to where I had seen signals from indoors yesterday. Quite by chance, I came across another beacon on a satellite at about 30° altitude and around 7° E, I think. This gave me some confidence that I might see the Oscar-100 (its new name) beacon. Here’s the unknown beacon:
Note that if you look at the details of these screen grabs, the filenames look as though they were taken a couple of days ago. That’s because I was using the RPi offline and couldn’t be bothered to set the clock 🙂
The appearance and disappearance is because I was playing around with the dish pointing to check it was real!
So, with the system clearly working, it was a case of looking carefully for Es’hail 2. I made use of dishpointer.com which is useful as the track to a satellite is superimposed on Google maps, which with the satellite view and enough magnification means you can see the correct pointing direction in terms of visible chimney pots and skylights! After a bit of faffing about I found the signal in the image at the top of this article, and then set about adjusting gqrx to get the best view of the signal.
Here’s some of that playing around:
The 956MHz is the RTL-SDR IF, so the received centre frequency is 10706MHz, the engineering beacon. It’s not spot-on because the LNB frequency reference is a lowish quality crystal with no temperature control. The dish is now pointed better, and it looks as though there might be two components to that engineering beacon. A bit more faffing about with the gqrx controls shows this up (960ksps gives a nice screen bandwidth to resolve the beacon, with 10x zoom on the waterfall):
The two carriers are about 2.4kHz apart – some sort of FSK maybe? They look solid at the speed my waterfall is running. You can see the frequency drift due to the 25MHz reference crystal in the LNB not being the ideal frequency reference. Perfectly adequate for consumer TV, not so good for narrow band amateur radio. A nice strong beacon though!
I went to have a look at the online narrow band and wide band monitors recently set up. The chat on the wide band page suggested video tests might be going on – I moved frequency into the wide band section and found a signal:
Not being into digital amateur television (and actually not familiar with modulation modes for digital television anyway – I must do some learning) I don’t know what that is, but it looks like some sort of digital modulation to me, or at least the barebones of one. The spectra I’ve been able to find online are much more mushy than that – stuff spread all over the place!
So – success! Apparently it opens for business on Thursday, so I will maybe have a look if the weather is OK. Here are some photos of the ground station hardware:
The bias tee I made recently is powered (rather excessivly) using the heavy duty psu normally used for 12V plus 36V PA requirements. The LNB is now on the end of a rather longer cable, so the signal at the IF receiver is quite a lot down.
Here’s the receiver – a cheap DVB-T dongle which uses the R820T receive chip, giving a frequency coverage up to 1766MHz which is fine for this purpose. The Rapberry Pi model 3B is in the white box, and the DVB-T dongle plugged directly into the powered USB hub.
This is the whole system:
So there it is. I will maybe think about transmit tests as well, but really I’d now like to press on with the deep space project, and receive something from near the Moon …