Posts by sv8qg



    ... but they differ in at least 3 places from the recommended design. The reflector is not as recommended. The material is not as recommended and the plug is not as recommended. I don't know about the patch thickness, but that also has a little effect. All of these deviations are perfectly acceptable, but can change the resonance slightly. The most critical is the distance of 3 mm and it is very difficult to correct it over the entire area - but this is not necessary because you can adjust it.

    Hi,


    I’m wandering if I can paint the hole POTY with plastic paint to protect the material from the salt water of the Island’s weather.


    Or what is the proper protection for the POTY to be long survived near the sea?



    Thank you Michael for the innovative dosing.



    73s


    Alex Lesbos Island

    The QO-100 S-band RX antenna is good in terms of circularity but not perfect.


    Good morning


    Thank you Achim, that's the point. Also thanks all of you for your comments, Rasto for the pdf, I had a lot of reading to do.


    I must apologize for my mistake about 3 DB lost in my downlink signal must be “3 DB less SNR as SDR console reports” I just remember it I updating to the new version 3.0.23 .


    73s Alex

    My personal rule of thumb is 1dB max between PA and feed.. (and don't forget the 0.1dB per connector).


    That’s why I’m using Hyperfex 13 .5” it has 1 DB @ 6m and it’s flexible compared to the Andrew 1/2 “ heliax.


    I prefer the electronics to be inside for weather protection – inspection and easy modifications with the penalty of more losses in the coaxial line.


    73s Alex

    Dear OM Rasto,


    Thank you for the nice paper I learn a lot. Yes POTY is 3 BD better that linear polarized antennas and Helix is ever better. My observation -and I spoke to 2 more Amateurs that they had the same experience- is If you have a linear antenna and rotate 90 dec the downlink signal from QO100 varies. My setup is 90cm dish and yagi at the focus, for receiving I have another dish 110cm, octagon FunCube plus SDR and SDR console. One thought I have is, that the geometry of the dish is favorable to the Horizontal polarization. But I had a change of my signal -digressed 3 db- few weeks now and I had to realigned few deg the yagi to gain again my max signal. All these measurements with the same receiving setup and always comparing with the Digital Beacon of the QA100 which had never change significantly. Either the propagation path changed (that’s impossible) or the behavior of the satellite antenna changed… any comments please from the sattelite gurus?


    73s Alex

    Yes, QO-100 Uplink on 2.4 GHz is right hand circular polarisation RHCP.

    In that case what happened to the satellite antenna few weeks now and I had to rearrange the orientation of my yagi to return to the previous max downlink of my signal??? It had dropped 3 DB and then returned to my usual max after correction of 15 deg .


    73 Alex

    But I have make a small experiement with 1 yagi only. If the yagi was horizontal (above or bellow LNB), the signal was noticable stronger than I try vertical (left or right). The difference was abt. 4dB.

    I have the same experience with you, I’m using a linear polarized uplink antenna for QA100 and I found that some orientation between vertical and horizontal are better than others. The mystery is that the best orientation for my QTH changed few months ago and my question is, “Is QA100 receiving antenna real RHPA?”


    73s Alex

    I have the same question and I’m waiting what SDR gurus will say and then I will do my choice.


    I think that Lime has already connector for external Reference, if that is correct it is a plus for Lime. You can avoid the Pluto modification, I’m waiting the other have to say about that.


    73s

    Alex

    All went well here with the upgrade from wim7 to win10. The only problem is that all the programs must be instalated from the beginning and that will keep me busy for some time. The positive is that I don’t need a new computer for some time.

    So what to do? Building a PA with 3 dB more power? Or buy a larger dish to compensate for the loss of MER? Or just living with these results the way they are. I think I'll do the latter.


    I personally prefer the solution with two different antennas if space isn’t a problem it’s more flexible and can be used for other purposes as well.