Posts by om0aao

  • Rotator for LEO satellites

    Despite that I was living in very windy location I have choosen very stable setup for LEO satellites, 6el. DK7ZB (50 ohm) for 2m band and 10el.DK7ZB (28ohm) for 70cm band. Both antennas with vertical polarisation only. Separation between antennas was 120 cm.


    It was cheap solution with an actuator arm and works well. The elevation angle was around 5° to 70°. Why?


    Pointing higher than 0° decrease local QRM and noise. Only few passes are more than 70° and if yes, in moment 70° to 90° is the bird nearest so it is not needed to point directly on it. Second thing, the rotator was controlled by SAT software with ERC interface https://www.schmidt-alba.de/eshop/ . In 30 second or less antennas were again pointed on it.


    On both bands were preamps used. Few times it was proved with winds above 120km/h and works well.


    Source SV1BSX https://www.qsl.net/sv1bsx/actuator/actuator.html


    But if You would like to buy a pro version, Alfa SPID is very good solution.

  • SNR of the CW beacon

    Thanks, Achim DH2VA ! But I am afraid that I am not very far from the real. I use signal strengh window which is showing maybe each second avg.signal strenght. First I tune on the beacon frequency, then few kHz away in free space.


    I have second LNB (uknown) so maybe I can try it with it. I think there can be difference, too.

  • RX antenna gain on the QO-100 / pathloss

    Thanks to everybody for a lot informations!


    I agree with g7iii that the WX can ruined signals. Both on downlink and uplink.


    Found that most stations use power 1 to 4 watts (30 to 36 dBm) and similar antennas but... the signals on the downlink varies more than 6 dB. That means some stations loose decibels somewhere.


    My question is if my station is working properly (NOT) and how weak signals I can receive.


    Now I can receive 1dB over the noise floor station with 24dB antenna and 25mW or 10dB antenna and 0,63W. As said G7iii - in ideal conditions.


    I will make more tests and try to make a small research... TNX!

  • RX antenna gain on the QO-100 / pathloss

    I am trying to calculate the pathloss and sensitivity of QO-100 transponder. Calculation:


    Au = 20 x ( - 4.622 - log f - log L)


    Au - pathloss in dB

    f - frequency in GHz

    L - distance in km


    My calclation shows that the pathloss is around -192 dB.


    My own carrier with 33dBm (2W) with 24dBi antenna is 20 dB over my noise floor. I am receiving with 80cm, LNB and SDR dongle. But I know that there are stations with better receiving conditions.


    My receiving floor:

    -192 dB + 33dBm + 24dBi + 20dB = -115dBm (0,4uV/50 ohm)


    But I don't know what's the gain of receiving antenna of QO-100. Did anybody knows that? And are my calculations right?


    What's Yours receiving floor?

  • LNB-LO: GPSDO or not GPSDO that is the Question

    DB6QS


    Using not modified LNB (PLL-type) with a SDR-dongle 0,5ppm. After 10 minutes warm-up it is very usable for SSB.


    There notable drift during outside temparature change. Especially when clouds moves around the sun it can bee courious. But still workable.


    I have tried software compesation with SDR Console 3.07 https://www.sdr-radio.com/Console/EsHail2 and seems to be good idea. I am running Atom n270 with 1GB and that's not enough, so sometimes I hear cracks in the output sound. But with better machine You can probably obtain good results.

  • WLAN grid antenna from WIMO suitable?

    I am using it too. The pattern seems to be clear. I have pointed it very accurate with a SDR receiver.


    With 2W seems to be good enough for CW. For SSB is usable but I miss some decibels to be pretty good readable.


    I am afraid also that the patch cable is RG-213 type, so the lossy one.


    If somebody would like to be strongh enough for SSB, needs around 8-10W with this type of antenna or try other one.


    https://om0a.cq.sk/en/amatersk…qo-100-es-hail-2-satelit/