Posts by G0MJW

    If you are interested you can look at the models for rain attenuation in ITU-R Recommendation P.837. https://www.itu.int/rec/R-REC-P.837/en with specific attenuation described here https://www.itu.int/rec/R-REC-P.838/en and its application to satellite links here https://www.itu.int/rec/R-REC-P.618/en - I wrote a tutorial a while back http://www.mike-willis.com/Tutorial/PF10.htm - anyway if you look at the maths it's clear why 10 GHz is much more impacted than 2.4 GHz.


    Specific attenuation γ = kRα dB/km where R is the rain rate in mm/hr


    Surely "Full Duplex operation is mandatory" means you should operate full duplex, not simplex, not occasionally checking but always full duplex? The key words here are mandatory and must. Very strong instructive terms. Rules are what they say, not what we might like them to mean, not necessarily even what we intended to mean. You can interpret rules as much as you like but you should obey them as they are written.


    Now what might be open to interpretation is the status of these rules. If they are in guidelines they are not enforceable rules in a legal sense like say the speed limit, but nevertheless everyone is expected to follow them.


    I find hearing myself 1/3 of a second later distracting, so I operate full duplex but with reduced RX volume on TX so while I can still hear myself, it's not quite so distracting. Also an SDR waterfall to check the signal quality and level. I think this meets the guidelines.


    Mike

    Interesting. I am not sure what an Orange PI is but that's a useful tutorial on how to use gnuradio.


    There is also the option of using an Adlam-Pluto and an Ethernet adaptor. Not sure using a HackRF is a good idea for new designs in 2020, plus you only need one Pluto as it does Duplex and it works out quite a bit cheaper.


    Colin G4EML has developed some software, also Gnuradio based, for the PI https://forum.batc.org.uk/viewtopic.php?f=129&t=6602 that makes a stand alone transceiver, not just for QO-100 but all bands from 4m to 6cm. It's not duplex yet, but can be.


    On a PC Simon's excellent SDRConsole can drive the pluto and several other network based SDRs.

    I don't see why not. I painted mine black to do the thermal testing. Only the coax got hot. The match hardly changed. This is just cheap car paint from a spray can. An alternative would be to make it out of gold, or perhaps cheaper gold plated copper. I think paint might be best.



    Thanks Michel


    A useful link. Question still remains what would be better for low rates. The examples assume something like 1 Mb/s whereas we are looking at more like 30-300kb/s. I was testing at 66k earlier and the video was OK but not great - like an 80s VCR on LP. I am sure it is possible to do better. The 333ks is fine but again, perhaps could be improved.


    Mike

    The box doesn't do very low rates, at least not well - when on my main PC I will send the profile for low bit rates for OBS. I can only find an out of date one from 6 months ago on my archive and there are better ones now


    66ks


    FFVCustom=preset=slow profile=main10 tier=high level=6.2 rc=cbr_hq


    35ks


    FFVCustom=profile=main level=4.0 rc=cbr_hq rc-lookahead=10 surfaces=2


    Tomorrow if I remember I will find the newer profile


    It's Tomorrow - or rather was but is now today, or would have been if now was then, whatever...


    The attached seems to work for 66ks 8PSK 5/6 - please ignore the muxer settings which are not right - they are largely ignored by the pluto but matter for other recordings. The important line is the one under video encoder settings. Also not the lower resolution helps, if you want to do good quality full high definition you really need to be using 333ks 3/4 or at least 250k 5/6. It also helps to reduce the frame rate if you can - see the video tab. Keep audio at 32k. OBS Record is used to send the data via UDP to the Pluto.



    Here are settings for 333ks 3/4 I am using this at 1920x1080.




    It's possible to go higher, especially with 8 PSK but 4K video only really benefits from higher bit rates. Static images are fine in 4K but anything moving isn't which undermines the quality. As the transponder is a shared resource high bandwidth needs only to be used when not causing trouble for others. Besides, who want's to see the average ham's mugshot in such high detail?


    Hope this helps.


    Please add better settings if you have them.


    Mike

    I am using Nvidia. Don't know if there is support for AMD stuff, probably. You set OBS up to record and set appropriate parameters. This is complex. See the BATC magazine and Wiki. What are you setting in OBS?


    An alternative is to use a hardware box like the H264/H2265 encoder that Evariste F5OEO's firmware supports.


    Mike

    It's probably formed a short between two pins due to electrolysis. With luck cleaning with an abrasive tool will remove it. Failing that hot air and PTFE tape to remove the SMD chips.

    At my location in JO22xx I can "see" the QO-100 from my garden, by pointing a dish parallel to my home, if the various apps are correct. That is good, if the sat was only visible from the front of my home, I need a permit to place an antenna...

    The direction of QO100 is almost exactly the same as Sky TV (UK) so getting such a permit, should you need it, might not be so hard. Nobody is going to be able to tell the difference without test gear. :)

    I would recommend going Pluto or LimeSDR and using SDRConsole. The price is very similar but the Lime is a lot more frequency stable. This setup is a lot better than a traditional transverter route and also sets you up for the future. Additionally you do not need to lock your LNB to a reference, the software can compensate for drift by tracking the beacon, though locking is best if you can. That saves buying a GPS reference until you know you want it.


    However not everyone likes software defined radio as there are no knobs to twiddle. For flexibility it can't be bettered and it's considerably cheaper too. You will need a bit more power with a small dish, I would not recommend below 60cm for SSB. Aim for 10W to be sure it's sufficient and there just so happens to be a 20W PA available at a nice price. With a 1.2m dish you could get away with a 5W PA, much cheaper but of course there is the larger dish needed. It's a trade off driven by your individual circumstances.


    Mike

    That's why there is a low pass filter built into the BATC Reference / DC injection IF out board. You also find the 25MHz will overload your SDR if you use the single coax method and don't filter it out.