Posts by G0MJW

    That's interesting as I appear to be getting full HD out of the OBS camera plugin, at least according to VLC and it certainly looks full HD. However I tend to use lower symbol rates so the limit becomes the channel.

    Using OBS camera is a fudge though, as it record, RTMP etc. The internal (non-plugin) OBS camera didn't include an audio channel, when I asked it hadn't even crossed their minds that this might be useful.

    It would be good if someone could get inside OBS and get it to produce a TS on it's own, the DATV plugin... the developers seem rather against this whenever I have asked about anything like that though you would think there would be a demand outside amateur use. Maybe it just needs a lot of people to ask.


    Well I did wonder. I am not aware it doesn't allow that. It could be Evariste does is automatically. I think you just use the standard commands. If that's actually the case it's simple enough to load the earlier version via the USB drive and eject and apply the standard command. Google should have found this as the top hit, at least it did for me

    Adalm Pluto -New official firmware 0.32

    Advice - use 0.31


    Yes - that's expected if the reference is not of very high quality or it's not being fed in at the right level. Incidentally that LNB looks more like a DRO based one than a PLL based one but I assume it is a PLL. The quality of the 25MHz is critical. Any noise on it is multiplied many times. For DATV use you are often better with a standard unmodified PLL LNB. This often shows up in the MER on the beacon.


    Here is my Bat file for 160kb/s. I see several differences.

    c:\ffmpeg\bin\ffmpeg -f dshow -i video="OBS-Camera" -thread_queue_size 512 -f dshow -i audio="OBS-Audio" -vcodec hevc_nvenc -s 1280x720 -bf 0 -pix_fmt yuv420p -b:v 80k -r 10 -preset slow -profile:v main -rc cbr_hq -rc-lookahead 5 -acodec aac -aac_coder twoloop -ar 48000 -ac 1 -b:a 24k -f mpegts -muxrate 160k -streamid 0:256 -streamid 1:257 -max_delay 2500000 -pcr_period 40 -pat_period 0.4 "udp://"

    You have that extra buffer and a very different network address. I tested this to VLC, it took a good while to appear but worked OK. So then I tried yours, modified to send to It also worked fine. So is it the IP address? Firewall maybe?


    When I do DATV reception using a POTY feeder the MER drops to about 4 vs 10 without POTY. The same poty feeder receive NB fine. I have test various LNB and POTY feeders with out a conclusion. Any proposals or ideas?

    What lens are you using. Do you have it at the focus. The usual reason for this is the wrong lens for the dish or not having it as the focus by trying to reuse the existing LNB mount but not understanding the lens needs to be at the focus, not at some mechanically convenient point dictated by the original LNB holder.

    The reason it works for NB is the transponder noise floor is much higher so what you are losing on receive is not apparent. For DATV, the same effect applies, but only for dishes larger than 1.2m with efficient feeds. Therefore it is much much more critical to adjust the feed correctly. Beacon MER is a good indicator, but bear in mind it depends on transponder loading.

    Very interesting - but the focus of the POTY is not in the same place as the reflector but in the middle of the lens, so it needs to move a few mm back. This is probably why it is worse. That's a challenge mechanically with that feed arm because the reflector gets in the way. The Rocket lens might be better. did you measure the F/D ?

    Well OK - but the POTY was never intended for long focal length dishes so it's not surprising a helix does better. What is the F/D of that dish? It looks like 0.7-0.8 which makes sense for a 4.5 turn helix.

    I see have a VNA so why show VSWR ? It only gives you part of the picture. It simply perpetuates the myth popular amongst HF operators that VSWR is all that matters. It's a parameter but not the only one and not even the most important. We are better than that. From the VSWR I can't tell if the patch is tuned correctly, which will make up to 3 dB difference in the uplink it it's linear instead of circular. The other thing about that POTY is the reflector is not the recommended 105mm circle. It might be OK. I don't know.

    What is surprising is the difference on receive. The Helix should be worse but given that's not the recommended Lens on the POTY. I have never recommended anything like that, I can't see how it could work. If you don't follow the instructions, it won't work so well. HB9PZKs design is several dB better, as it the originally recommended Rocket Lens. If it really is so very many dB worse there is something not right - like the focal position or the wrong lens, or both. The feed looks too far forwards but that's not easy to tell from the Photo. The gain of LNBs varies widely so it's signal above noise that matters. A number in dBm is meaningless without knowing the gain. Was there some gain calibration done here?


    4Msymbols. It locks fine. I just doesn't decode the data.

    This is not on the satellite. It's DVB-S local repeater. Line of sight, 20 dB C/N. No multipath. Rarely it gets a frame but soon loses sync. I have given up as I don't think the package is able to do this at the moment. Something is probably broken so I will wait for the next version.

    I just can't get this last version to work in DVB-S. It locks to the signal, nice clean constellation, but it refuses sync. Does anyone know if this actually works in DVB-S? 4Ms?

    The question was : when I adjust the POTY for optimum SWR moving plates does the circulation affected?

    Yes. PLEASE DO NOT ADJUST LIKE THIS FOR MINIMUM VSWR. HOW MANY TIMES MUST I REPEAT THIS ? The same point comes up again and again and again. If you tune like that the chances are you will produce a linear antenna. HF DXCC types old antenna lore does not apply! POTY is a complex antenna.

    Now to get those resonances right build accurately. Exactly 3.00 mm spacing. No deviations in sizes, correct connector type. To tune if required use a vector network analyser and look and what's happening on a Smith Chart. If that's too difficult, perhaps ask someone for help. Really it needs the proper tools. If you really can't find a VNWA find where it is matching. If it's high gently bend all four corners towards the reflector just a little. Do it evenly and symmetrically. See what happens. If it's really far off frequency the dimensions are not correct.

    Here is mine - before and after.



    I would suggest doing some research on the Lime boards. It strongly depends which frequency band output you have selected. Perhaps the newer one is detecting differently. It could also be broken or the match makes it appear so. But does it really matter that they are different as long as you know? I would not run the lime anywhere near peak output.

    It looks well made. A ruler will not be accurate enough. Do you have a 3mm drill bit for example?

    What you need to do is find something 3mm thick (exactly, not approximately) and put it between the plates to measure the spacing. A metal shim is good for this. If it is not 3mm then you need to make it 3mm by resoldering the patch with a blowtorch or hot air gun. If you use a damp cloth behind you can prevent the reflector and connector from unsoldering while you melt the solder on the patch.

    Some people found a slightly under 3mm (say 2.9mm) aluminium shim between the plates is a good way to get a 3mm spacing. The difference allows for it not being easy to ensure it is tightly compressed together when at 350c. When that's done you should have a good match but if not it is possible to adjust be very slightly bending the patch. However you really need to have access test equipment to do this. They are only $60 for a Nanovna working to 3 GHz, but I recognise that unlike in the UK, you can buy a lot of beer for $60 in OM, so perhaps the local radio club has something they can lend?