Posts by G0MJW

  • Signal Quality!

    Hi Johannes


    Unfortunately these sort of people do tremendous reputational harm to the hobby. Usually when someone takes a stance like you describe above it is due to their lacking technical abilities or resources to fix the problem. They have possibly spent a lot of money and are in self-denial that all is not right. They often reject criticism, especially where they know deep down that it's true. There is little we can do about such attitudes other than offer to help them fix it.


    Mike

  • POTY and return loss plot

    There is not always a loop, the inflection cusp at the marker point. Don't worry about the loops on a larger span, it looks like your calibration plane is not at the antenna but perhaps some distance away. If I had the inclination and more information I could work out how far.


    The real test is does it work? Transmit a known power, do the link budget. Is it in agreement with your measured result?


    I think it would help people a lot is AMSAT DL would come clean with the actual measured performance of the transponder and a real sample link budget. If they can't due to an NDA or do not have the technical capability, I will work with some friends to measure it as best we can.


    Mike

  • Signal Quality!

    Absolutely. If operators can not generate a clean signal or even worse do not understand they need to they should not be permitted to transmit. The lowering of technical requirements for a license can not extend to reduced spectral purity. Firstly, as a community we need to let people with poor signal quality know and help them to fix it. Secondly, persistent abusers, the sort that tune up and down while transmitting to find their signal, regardless of what interference they cause, those that use excessive power and those otherwise behave disruptively need to be firmly dealt with through the licensing process.


    Mike

  • QO100 phrases/talk

    What I don't understand is this idea of DX.... The DX are often closer to the satellite that we are. My path to Remco is longer than the path to some exotic station in Africa or India and we are basically working through a transponder so the HF DXCC propagation element is pointless. Contacting like minded people in other places and discussing things is the point and it doesn't matter where they are.

  • DATV Beacon A71A C/N and signal strength decreased?

    It is about 10.3 dB this morning but I have noticed it falling as low an 9.8dB in the daytime, lower if there are other strong signals.




    The beacon is a bit too wide for my liking and reducing it to 1 MS or less would help with the over-crowding we are now seeing on occasion. Some stations like to transmit 1 MS and we can only accommodate two of these with the current beacon. Only one 2 Ms signal is possible and nothing wider. We all had fun with experimenting wider signals when the beacon was off. Perhaps even 500ks but H265 would be a good compromise.


    Meanwhile, several of us have been experimenting with lower bandwidths and higher order modulation. 66ks is 33ks are very usable and can be done with low power.


    Mike

  • All-in-one-box solution for Oscar-100

    My multibox solution - needs a laptop too. One day I will get it more integrated..


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  • Minitioune Software and New Windows Installations

    This is a puzzle - I recently bought a new laptop and had no such issues. It has Nvidia graphics though. VLC does render the video so it's something to do with minitioune. It might be best to ask on the vivadatv forum where you downloaded the software.


    Meanwhile, can you show is your grf filters? I will find mine on another PC and show later.


    Mike


    Edit - sorry, I forgot the later version 0.9 doesn't use grf files any more so you won't have those.

  • Dish / Antenna Alignment

    Quote from G0TKZ

    Thanks guys for the follow up..!

    Any ideas what the manual settings would be for the DVB-S box to receive the wide band TV beacon from Es'hail Sat..?

    cheers...!

    None - it will not work as the Beacon is DVB-S2. Most boxes these days are, if your is then set the transponder frequency appropriately, set 2Ms and search. For this to work the LNB has to have been modified to a lower LO so that the IF falls within its' frequency range. With a standard LNB the beacon will be below the minimum 950MHz tuning range of standard boxes.

  • T/R switching

    I was just thinking of designing a simple sequencer PCB to drive relays and supply voltage to the PA after a small delay. There are many of these available already but either expensive or not quite what I want.


    Another issue with the IC9700 not having separate band by band PTT signals I was considering if the External Preamp voltage could be put to use for this. Gated with another signal to ensure the PA is not permanently enabled when the radio is turned off or on another band. I can't think of a solution yet except perhaps pre-amp voltage lost and PTT enabled. Maybe something can be done via CIV.


    Mike

  • Dish / Antenna Alignment

    That solar method won't work is you live in the North West, or at least only rarely. If you find the elevation calibration is out it may mean the feed is not located at the correct focus. This can happen if the feed is modified to fit 2.4 GHz.


    Mike

  • Excessive Power

    Hi all, as many new users are appearing and with no Lila its probably worth mentioning the point about excessive power. Some new operators are using 20W PAs at full output with larger dishes.


    Here is an example, which I am sure wasn't intentional and it's about gaining experience and new operators coming on to satellites. It wasn't doing any harm with the transponder empty and the operator reduced power once it was pointed out, but initially their signal was well above the beacon. The signal should be at or below the peak level of the CW beacon on a single tone, it should not be at the same level within the full bandwidth on an SSB filter. I appreciate it is very hard for operators not using SDRs to set these levels which is why monitoring on an SDR or on the WebSDR is recommended.


  • ICOM IC9700 and QO100

    Quote from David G0MRF

    I have finally joined the 21st Century and have a 9700 awaiting collection in a few days time.

    How are IC9700 owners driving upconverters?

    My upconverter needs 12mW drive and I don't want to damge it. At the moment I have a FT736R running about 5-10W with a 10W attenuator. But the 9700 output power is an order of magnitude higher.

    spikes in the first few milliseconds of TX and power output changing accidentally with an unintentional mode or memory change are worring possibiliies.....

    Which is one of the reasons I specifically do not use it. I would suggest a 34dB attenuator as it is easy to make with a 50 Ohm 100W load and a BNC T-piece. Use a 1.2k resistor from the centre. Connect the far end to a 51 Ohm resistor to ground and take the output from across the 51 Ohm resistor. If you need less attenuation, reduce the 1200 Ohm series resistor appropriately, e.g. 510 Ohms will give 27 dB, 330 Ohms 23.5 dB. Lower values give a progressively worse match but not so bad as matters.