Beiträge von g7iii

    DD4YR : Not measured it tbh, but was able to receive signals well when 'our' transponder was tested on 23rd December. Unfortunately I didn't record signal levels.


    Can confirm 10706 is the 4G/Mobile phone issue for me (and switching to 10600 LO drops the frequency below what my SBX can do)


    G3WDG : Totally agree we need to wait to draw final conclusions, I was just comparing delta of the signals received on each dish, and only quoted the margin. Noise with the 45cm dish was -121dB, signal at -111dB. The "Big Dish" [which I haven't named Arthur - Yet!] had noise floor at -116dB and signal at -90dB


    And Johannes and Peter are of course correct with regards to the splitter's impact, I was overly thinking things with the splitter inline :)


    The Pluto has now seen signals on the 1.1M dish, with -90dB noise floor, and -80dB signal. Interestingly, the FCDPP is now showing -88dB noise floor, and -71dB signal on the 1.1M. But then again, the night has come, and it has got very windy here (which means the small dish has been blown off the garden table, being only table top at present!)


    All figures are as shown by gnuradio QT Frequency sink and are relative...

    I have long wondered just how small a dish we might be able to go to (one of my other interests is in Emergency Comms)


    Since others have tried 50 and 60cm dishes, I thought that since I had a small 45cmx35cm dish available, I would see if I could receive the 11205 V Beacon (10706 I have numerous issues with)


    A back to back comparison with my 1.1M dish was carried out. Pointing may not have been identical, so take these figures for what they are - A Quick test on a Sunday Afternoon.


    That said, On my 1.1M dish I was receiving the beacon with 26dB S/N. The 45x35cm only received the beacon with a 10dB S/N margin, 16dB down on the 1.1M dish


    I've also been having limited success with my FCDPP and RTL dongles (A Mixture of gain settings and potentially frequency selection etc, however on my 1.1M dish the FCDPP (serial way higher than Peter's) I was receiving the 11205 beacon with an 18dB margin. My RTL dongle was far worse at just 6dB margin. It should be noted that there was a 2 way F connector splitter in line, so add at least 3dB to those margins (Probably more).


    I'm yet to get my Pluto to hear the beacon at all, although that is the next test. With the 16dB loss between the 45cm dish and 1.1M dish, 45cm may not be entirely out of the equation, for narrow band work, although of course we need to take into consideration that the 11205 beacon will be nothing like our transponders



    73s


    Iain

    That's pretty interesting. Now an extra satellite meter has just arrived, on Saturday I should be testing my own 45cm x 35cm dish, and able to compare it against my 1.1M dish, and against the calculated differences in gain

    Hopefully I will do some measurements of my own Octagon LNB's in the next week or so, although I intend to measure over a 24 hour period as well as short periods.


    I also have a gnuradio flowgraph to measure a carrier's frequency. It will not be much extra code to correct the receive frequency, thus hopefully keeping the carrier 'straight' within the pass-band.

    It is a very nice Christmas present indeed :) Both beacons have been spotted here in .UK on my 1.1M dish. Like others, signal strength varies, but that's to be expected with Melco doing IOT.


    The 1,1M dish is far easier to point than I feared...Find 28E2, then move towards south until 28E2 drops out, then one more nudge towards south and there it is! Should be even easier when P4A gets to 26E

    Hi Pat,


    I'm guessing your 10706 Beacon is Es'Hail-2. Your 11205 one is more likely Astra @23.5 East, unless they have turned modulation on 11205 (up until now it's just been a pure carrier from what I've seen, and I think yesterday or the day before it dropped 25db, according to some). Your 10951.5 waterfall is almost certainly Astra 2C

    Looks like I can now copy both beacons both about 16-17db above the noise floor - The pointing angle of a 1.1M dish is very sharp at 1.8 degrees. Thankfully it's locate 28.8E and move south until the satellite meter drops to 0, and then nudge it further towards the south a tiny amount!


    This week I hope to modify the gnuradio carrier measurement code I have, and hope to run a long term (24H+) measurement of the carrier frequency. This should (If my system is good enough) echo Daniel's doppler measurements


    [Biggest issue I have is the LNB stability, and the fact my SBX appears to be ~900k off frequency, unless it's the LNB that's off that far, or a combination!]

    I have a Octagon Dual Output LNB (Happened to be going spare, I'm keeping the PLL one safe and warm in the house until P4A is officially activated), so I checked the frequencies in question. I found strong carriers right where Christian did,using my Ettus N210 with SBX board, 5MHz bandwidth, tuned 1MHz off the frequencies above, carriers showed up +1MHz up from the centre exactly where expected however:


    1) They were there when I moved the dish well away from 24E

    2) Switching polarization seemed to have no effect on them

    3) They were there even with no power to the LNB


    I rather suspect a local source on/near my IF (699MHz/749MHz) , certainly in my case.



    73s


    Iain

    Hi DB8TF,


    Along with my planned ranging and timing experiments, I hope to be doing something similar, having discovered just how many potential feeds I have in the 'junk box'. I'm also hoping to be comparing the linear polarisation loss in conjunction with my local radio club who have a 2.4GHz TX and Linear Polarised YAGI (they just need a new Crystal...)


    It will be very interesting to characterise just how low we can go with regards to both uplink and downlink budgets. Just how small and really portable a station can we build. I have some 45cmx35cm, can acquire 60cm, and have 90 and 110cm dishes, so fully intend to test them all. A 16db gain helix is another option that I hope to test (comparing that to the LP YAGI should show up the LP loss)


    (And any that don't work can be used for other projects, such as a Solar Radio Telescope, Or terrestrial use!)



    73s


    Iain

    In that case I have another bit of the required uplink bits...actually two...Even if they are a little large for small dishes, and likely to over illuminate! Now to find some way to mount them :)

    Hi Guys,


    Can someone confirm for me...I know the uplink is RHCP. That means I need a LHCP feed right in the case of using a dish ? As my signal is bouncing off my dish...



    73s


    Iain

    I checked the specs on this particular model According to Farnell (Hit the first link I found..),and that particular model is rated to 100 Watts, But as Achim says you want to be cautious to safeguard your nice 2.4GHz PA

    I've been retrieving the TLE from Spacetrack each morning, and indeed it may be quite close to it's parking spot (it was not far from GEO from what I saw of the numbers). That said, it was still approaching Earth, and lower than the GEO belt, so I guess maybe another orbit at least

    Hi Peter


    With regards to perhaps someone will write an SDR code which will automatically track the beacon while receiving other signals:


    I now have gnuradio code that measures a carrier frequency down to 1Hz in a 250kHz bandwidth. Tests have been carried out using terrestrial sources, some strong, some weak(MSF on 60k, DCF on 77.5k TDF on 162k, RBU on 66.6667k , and RWM on 4996 and 9996kHz.)


    Without a 10MHz reference my USRP N200 appeared to be up to 6-10Hz off at 9996kHz (although some of that may have been atmospheric of course). Multiply that up to 10GHz and you get 6-10kHz. With a 10MHz reference, 0Hz off!


    RWM is very weak here on certain frequencies at certain times of day, but I can still get a 'Lock' even then, next steps are to test with space sources (AO-73, Nayif-1 are targeted for later this week, and maybe JYSAT-1 as well once she launches.)


    I also have some early ranging code (Sorry Achim, only carrier at present, Spread Spectrum will be have to wait), that I'm hoping to test to at least some degree with the same spacecraft assuming I can confirm a good uplink to them


    The carrier measurement code has also been modified to measure to 1kHz rather than 1Hz. That version can run on a Raspberry Pi 3! I am planning to see how accurate I can reliably go with a Pi 3 (I do not expect to get to 1Hz, but fully expect to be able to manage somewhere between 100 and 10Hz)


    Also working on separating the different sources of frequency drift (Lack of GPS lock on uplink, LNB drift, doppler (due to dinuaral effects from the Moon) etc, and am hoping to measure the figure of eight "wobble"



    73s


    Iain

    Just as aside, a LNB+RTL dongle+ Your chosen SDR software should suffice for the downlink, even providing a nice waterfall so you can _see_ as well as hear that you are no stronger than the beacon, and not transmitting over others.


    This would then let you use a single single-band trx just as an uplink.


    I certainly intend to have at least one dongle constantly monitoring at least one beacon just as an extra receiver