Mounting of POTY on dish, SWR high, how to fix?

  • 10m length of H155 with an N connector

    Hi Bill,


    the attenuation of your H155 is about 5db @2400 MHz and i guess the N Connector is a cheap part from LingLing (here for cheap chinese goods). So you only have 1/4 of the power on the feed. The H155 is not usable for 2400 MHz. The RL is only 15db @2400 MHz (SWR 1,43) Look at datasheet from Belden.


    73, Frank

  • Hi Bill,


    the attenuation of your H155 is about 5db @2400 MHz and i guess the N Connector is a cheap part from LingLing (here for cheap chinese goods). So you only have 1/4 of the power on the feed. The H155 is not usable for 2400 MHz. The RL is only 15db @2400 MHz (SWR 1,43) Look at datasheet from Belden.


    73, Frank

    Frank,

    I knew about the 5db+ attenuation from the coax but did not consider the connectors, thank you for reminding me of those. I thought that a 6db loss would not be a problem, as it would give me 10w at the antenna, more than enough for QO-100. My friend also has 20w and the same 10m H155 cable and he has more than enough power.


    Thanks to Wilhelm I just learned that my main problem was that the my has an SMA-R connector. When this is fixed I'll try again and report the results. I'm not sure there is any coax better than H155 available here in Slovakia. If it is too lossy I'll have to order something online. What would you recommend? I've heard that RF240 is a bit better than H155.


    73, Bill

  • Hi Bill,

    test it with your H155, i think it will be ok.

    Good luck

    73 Wilhelm

    Wilhelm, you are correct. I used an SMA to SMA-R adapter on the end of the 10m H155 coax, and now all is working fine. I have moved the shack inside and am very happy. Later I will replace the BamaTech on the new dish with the POTY/LNB combination, so that only one dish will be needed.


    Thanks to everyone who replied and helped me with this project! Hope to have a QSO with you on QO-100!

    73, Bill

  • Ahoj Bill,



    a H155 coaxial cable is not good choice for Tx use, especially for higher power. This cable, thanks to its structure, produces a lot of intermodulation ( tested in our contest station OM6A). You can get any good quality cables + connectors in Slovakia. See www.ges.cz, www.gme.sk  www.tme.sk etc. Even you can order professional cable assembly for reasonable price here: https://konektor-kabel.cz/. Here, you can select good quality stranded or hard-line cables + high end connectors (Rosenberger, Andrew, Spinner). I do not recommend you to use no name shiny connectors. These connectors are working with acceptable impedance match (20 dB) maximum up to 70 cm. They have impedance match less than 13 dB on 13 cm.


    Good luck with your satellite project.



    See you on transponder,


    Rasto OM6AA-A75GR

  • Very clever! But even with no adapter, the female N connector barely passes. The male connector would not pass. Could I extend the arm so that the mount/adapter attaches lower on the POTY, away from the N connector, as in the drawing below?


    Mike,

    Here are a few more photos. The prior owner says this POTY has been tuned and tested. I measured just under 4mm with a ruler, I don't have calipers, the measurement could be off. Also, the only available coax I have to connect the PA output to the POTY is a 10m length of H155, that probably loses half my output.


    I just tried the BamaTech feed again and it is still working, I see my downlink and swr is low.


    About to make my POTY but thinking of using an SMA socket instead of N Type.

    However, I am concerned about losses with making some form of pig tail to convert from SMA to N Type.

    I am unable to find a suitable made up pig tail with a SMA plug right angle to N Type female.

    What solutions are stations using?

    Does anyone know of a supplier which sells suitable made pig tails?

    Thanks