Beiträge von DH2VA

    Found the problem. My SDR Stick is based on an R820T and this seems to have no RX at the 11205 IF (which is 1455 MHz), some sources claim the coverage ends at 1300 MHz. Connected an Airspy and all is fine.


    For sanity, checked the ASTRA 3B at 11446.75 H. Huge beacon..

    Tried to switch my pol to vertical (mechanically .. ) still nothing at 11205 MHz. Questioning my antenna alignment now.. but 10706 is strong with all sidebands. Hmm.

    What are you people with the 11205 signal using as hardware? I have an unmodified PLL LNB with RTLSDR behind and power injection.

    Hmm.. cannot see anything at 11205 MHz, but I am currently at horizontal polarisation. Do do however see something coming from the sky at 10951.5 MHz:

    Anybody can confirm this? I do see the 10706 signal with its sidebands and the stepping tones at the full hour and half hour..

    Could you please specify which test you are referring to? Actually DG0OPK confirms the excellent behaviour of the D75F.

    Does someone know what signals cause those "lines" every few khz in the spectrum as seen in DL3CWS second pic?

    If you mean the lines at +- 15 Khz: that is the engineering telemetry. The carrier in the signal is the residual carrier, as the beacon is BPSK modulated .. maybe not with +-90 deg phase phift (as the carrier would be non existing then) but something like +- 60 deg.

    I am not quite sure about your setup (maybe I misunderstood, my apologies!), but if you use the Andrew T2400 Reflector with a LHCP feed, you will still get a linear signal.

    The reason is the large spacing of the reflector gaps in one direction. When used without mods, this reflector will only reflect one polarisation plane and be transparent for the other. If you want to use this reflector for circular polarisation, you have to line it with a mesh which has a mesh opening of < lambda/10 (so less than 1.3cm) (rule of thumb).

    Maybe you mean Faraday rotation. A linear radio signal will rotate its plane when passing the ionosphere. However, if the receiving antenna is RHCP (as it is for Phase-4A), this has no influence on the overall radio link, even if the transmitter is using linear (you just lose 3dB). If you receive linear as well, then of course any linear mismatch will cause 'fading'..

    Because 'horizontal' is referenced to the local system. Linear H in Europe and linear V in Brasil generate the same signal at the satellite. RHCP will always be RHCP when it reaches orbit, no matter where it originates.

    For uplink we chose this as this is kind of S-Band standard and space rated antennas are easily available. The same is true when using linear on X-Band downlink (as you might see when checking your TV satellite programme settings). We need both polarisations to decouple the WB and the NB transponder and as the local definition of horizontal/vertical is depending on your location, you need to apply LNB skew, which can be calculated here:

    Satlex Az/El/Skew Calculator

    Without knowing any details, it typically takes about one week to get into geostationary orbit (on a test position which is NOT the final one). Then the in-orbit testing starts.. and as said before, our transponder will likely be last. I personally do not expect any transponder opening in 2018. Please stay tuned, we will announce news as we have them.

    Most important of all: do not transmit unless the transponder has been officially declared open! Doing so will only delay commissioning and the release date for all. Last but not least, any misbehaviour of users will not help our good relationship with Es'hailSat and we all want to keep it good, do we?

    Maybe nothing except for the polarization mismatch loss. But as these antennas are not rated for high (>=10W?) TX levels, you might run into problems here. This needs to be carefully tested, best with a circulator to prevent bad things from firing back into your PA.

    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

    Iain,

    this sounds like an exciting start! I am sure once the transponder is up and running, things will develop very fast!

    Dear friends,


    without (!) having an official launch date one can certainly say: we are getting close now. On various places in the internet different launch dates are being listed and on this occasion I would like to communicate or clarify a few things on behalf of the Phase4-A team.


    - There is NO official launch date yet. As of today (October 29th) there are only NET data (not earlier than), which are derived from different indications, which can be found from more or less official places in the internet.

    - NET means: certainly not before. But also means: probably later, unless EVERYTHING goes smoothly.

    - For various reasons (last but not least respect towards our 'hosts') AMSAT-DL will not participate in such speculations (and nothing less are NET data for us).


    - SpaceX will (as usual) perform a static fire test about 5-7 days before the launch attempt without payload. The launcher is lifted on the pad and the engines are ignited for a few seconds. If this test does not reveal any problems, SpaceX will officially announce the date for the launch attempt shortly afterwards (a few hours).

    - The rocket is then taken off the pad, the payload is mounted and back it goes. Of course delays can pop up at any time...



    Personal note: I plan (with a few team members) to go to Florida to the launch. I haven't booked any flights or hotels yet, maybe this gives you a feeling how feel about the rumors right now.



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    Spoiler alert: for the next AMSAT-DL Journal I am writing an article about how SpaceX gets a satellite (NOT Es'hail-2) from the pad into the transfer orbit and how it continues from there. This is based on existing data of an already launched payload. Also here: no info about Es'hail-2... because there are none.


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    Let's all take a deep breath and enjoy the launch... SpaceX will offer as always a great webcast.


    73s Achim, DH2VA