Posts by G0MJW

    That looks good. You are right it is critical on tuning, this is 2.4 GHz after all and it doesn't take much movement to make a difference. It really helps to be able to see what you are doing, hence the smith chart. You are aiming to get that little loop in the centre

    Look at it with a smith chart. Ideally follow the instructions in our original article.


    Oh yes - and use a more sensible scan width - say 2.3-2.5GHz as otherwise the smith chart will be too messy on the screen. This should give you a much better idea of what adjustments are doing. Don't aim for a very good return loss, 20dB max or you will not be operating with the correct resonances.

    Be careful ordering just now - the current N-type units are the same hardware as the SMA. Nothing wrong with that. I was tempted but I own a good set of SMA to N adaptors which amounts to the same thing. I would like a larger screen though and a metal case. Hoping these will be available soon on their own as an upgrade kit.


    I think at some point soon there will be a new version designed specifically for the 4" display, or maybe bigger, with SMA or N in a metal case. It might therefore be worth waiting a bit. There is also a 6 GHz version being developed and work to improve the receive port matching. Then you wait a bit longer. What to do with a now redundant Nanovna V1.


    It's really quite remarkable what's been achieved here, it's not up to professional standards, those VNAs cost thousands, but it's more than good enough for most amateur purposes.


    Mike

    Thanks Mike I have ordered one of these from Amazon, It looks way to complicated for me as I have no idea how to read a smith chart but I will have a look at some tutorials on YouTube and see what I can do with it, My Normal Analyser only covers to 230mhz so this will be handy to have for 70 and 23cms as well,


    73

    Trevor

    EI2GLB

    You don't have to use the smith chart - though good to learn. It will do all the usual plots. It is important to properly calibrate to get the best results.


    Mike

    :thumbup:   :thumbup:    :thumbup:

    I am completely agree with your opinion for 333ksym DVB-S2 and 100% support this idea and all the people who share this idea !!!

    But we all know that there are still many pensioner among us who want absolutely nothing to do with a computer, they just want to TX a switch to ON, turn ON the camera and send !!


    Translated by google.

    This is exactly what Portsdown is. A transmitter without computer features. It is based on a PI of course but can order an SD card image. All controlled from a touch screen. G8GKQ and his team have developed an incredibly flexible system anyone can use.


    Mike

    Hi Laurent


    Most of these Ethernet not working problems are due to the USB to Ethernet adaptor, either not being compatible or not getting sufficient power. The problem is adaptors that look identical might not have the same hardware inside. First thing to do is try another and the other thing to do is ensure it is powered and that normally means a Y cable or hub.


    Mike

    I am not sure I agree. It's the 21st century and DVB-S is 20th century technology and getting old. Such a system might be easy to use but there are not so many wide channels. 1Ms DVB-S requires much higher power than say 333ks DVB-S2 and generating power is the most difficult bit.


    A more modern solution is the BATC Portsdown project. This does all that and much more and arguably does it better because it also does low SR, DVB-S2. H264 and can be made to receive as well. The transmitting hardware is not challenging, a Raspberry PI, a touch screen, a webcam and a Lime Mini. Perhaps we need to translate the instructions into the German language to make this project more accessible.


    Mike

    We can calculate pretty much exactly what the SNR should be. I don't think we are going to discover anything new here so it's more around helping new users determine how well their equipment is working. In full duplex you optimise your uplink by looking at it's spectrum and making sure it's clean. Regrettably there are many people who were sold black box solutions who frankly have not a clue about how satellites should be operated and because they are incapable of monitoring their own uplink because they decide to use an HF radio as driver they transmit excessive power, splatter all over the place and call off frequency. If the same station is also deaf, they don't see their splatter, but everyone else does. Such is life.

    They are not visible to anyone. You need to work with it under a magnifier. The gain in dexterity with the feedback from the magnification is remarkable. So you can do it. You just need to practice on something less costly first.

    I was sending DATV last night with 15W and a 1m dish. Don't think because you are QRP you can't play. While you can't send 4K video in a 1MS transport stream with such low EIRP you can send perfectly viable video at low symbol rates.


    Mike

    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