S21RC QO-100 station build from scratch - discussion and help

  • Hello OM,
    Greetings from Bangladesh. I have been gathering as much info I get about activating QO-100 - very interesting, I have the following two questions, can anyone please advise:

    1: Minimum Antenna dish size for receiving QO-100? (off the self Ku Band 80cm DTH antenna would be easy to stealth as DTH).

    Info: From my location the antenna elevation angel is 15 degree - almost at the boarder of sat footprint. Please see attached.

    2. SDR or Icom UHF radio (by modifying LNB PLL frequency)? Which one would give better receive?

    My plan is to RX first, if all works then will work with TX.

    Thanks in advance, 73, Fazlay, S21RC

  • Hi Fazlay.

    1: Minimum Antenna dish size for receiving QO-100? ?

    The elevation here (Brazil) is around 10 degree and many stations work with antennas between 60 and 90cm.

    I worked portable in GG88HG (Juiz de Fora - MG) inside the hotel with 75cm dish:

    [Blocked Image: https://cdn-bio.qrz.com/n/py1san/HH88HG.jpg?p=ded797c9461a578420de6931737016b4]

    2. SDR or Icom UHF radio (by modifying LNB PLL frequency)? Which one would give better receive?

    I prefer SDR. I like "see" all the NB Transponder spectrum.

    73 !




  • Thanks a lot Sandro. That's good news for me. I like your hotel setup :p I am sure you had a "NO DISTRUB" sign hanged on the door the whole time you were there :D

  • Hello all,
    Here is the plan for my setup. I am concern about the following two issue:

    1. The 15m run of coaxial in the TX chain. Can you advise if this would work? It is difficult for me to put much equipment at the antenna site (i.e. remote SDR using a small RaspPi/OrangePi).

    The cable is similar to LMR400, and attenuation would be around 3.3 + some more due to the N-SMA pigtail.

    2. Tapping DC power from the RX cable, faltering with inductor and using a regulator for the TX driver and PA.
    Or: is it better to insert the DC power in the TX cable?

    Please advise.
    Thanks in advance, 73, S21RC

  • Hi George,
    Thanks for pointing it out, I have tried to do the link budget as best I could (this is my first system which will be above 70cm) - there might be error.

    Can you please check if this should work (I am confuse, in this site it said minimum PEP is 10W for SSB/NB, does PEP and EIRP same?)

    Clarification: If both the 8w wifi PA and SPF5189z has 12dB gain, then why use the PA and not another SPF5189?

    Thanks a lot in advance, Fazlay/S21RC

  • Hi, it looks correct. The SPF5189 can reach this output power at maximum. Consider a few dBm less. The reason for not using a SPF5189 at output is that it has the same gain but cannot produce the required power. Maybe you need to lower the output of SDR, add BPF between amplifiers (if you see self oscillations-if you can see them...) Or add an SPF5189 between coax and final amplifier. Also I have noticed increased attenuation slowly over the time at 2.4 GHz.

  • Thanks George,
    I have ordered two SPF5189 so can play with it as you suggested. Waiting for all the modules to arrive, it's been shipped from China.

    ** I do not have Spectrum Analyzer or 2.4GHz Power meter - so difficult for me to measure gain/attenuation. Best I can do is make the diagram as much full proof as possible with enough margin not to distort output but able to reach the bird.

    Meanwhile will install the RX part and also TX cabling this week and update you all.

    Thanks again for the help.

    73, s21rc

  • Update:
    60cm DTH offset antenna, unmodified 25MHz Xtal LNB - SDR Console locked to beacon.

    Receive S9++ signal from my location (NL53er, elevation 14.9 degree). Monitored some station. Very clean signal (Leila was activating too frequently).

    Now waiting for the TX parts and TCXO to arrive. Meanwhile will make the Helix antenna and keep it ready.

    73, S21RC

  • Congratulations Fazlay s21rc .



  • Dear All,
    I need help from you the experts who have already done this many times. (I do my reading/searching and only post when I can't get it or understand it. so please bare with me.)

    Two help needed:
    1. TX Antenna made and tested - following DC8PAT 's design (his 3D files are big help) - attaching is a picture of the capacitor match and the VNA graph. Please advise if it's ok? I am concern about the tuning capacitor plate - to bring the antenna to 2400Mhz It went the other way compared to picture of other users.

    2. I have the TX SDR (0.5ppm TCXO), LNA [extra one unit ready if needed], PA 8W [optional 2W for test], Helix antenna with bulls Eye TCXO LNB. Missing is the BPF (lost in transit :p ). Instead of waiting for the BPF can anyone give me a microstrip PCB layout so that I can eatch and scrap with knife to tune at 2400MHz Fc? (Please do not advise SAW filter module - that will take another 2 months to arrive If I order today)

    Cavity will be difficult for me as machining/milling is difficult for me here.

    Waiting for your valuable feedback.

    Thanks, Fazlay S21RC

  • s21rc

    Changed the title of the thread from “Minimum Dish size for QO-100 receive from S2 location (23N 90E )” to “S21RC QO-100 station build from scratch - discussion and help”.