Hi Bob, Your calculation is close to real with QO-100. With ERP = +55 dBm we have about 30 dB S/N on RX side. If so when we changing the TX LO's PN level from 120 dBc/Hz to 90 dBc/Hz we lose only 3 dB in terms of RX S/N? Not sure if you can even notice ...
Karen, ra3apw > > Hi > > Assuming you know the power level you will be delivering to the sat and the > noise figure of the > receiver on the sat, the calculation is just as presented earlier. If the antenna > on the sat has gain, > that also gets into this and that. > > Using some made up numbers, since I do not have the real ones for this > exact system: > > You start out with +50 dbm ERP from your antenna. > You have a link loss of 190 db. > The sat antenna has 1 db of gain. > > You are delivering 50 - 190 + 1 = -139 dbm to the sat. > > If the noise figure of the sat reciever is 3 db, then it?s noise floor is -174 + 3 = > -171 dbm > > That puts a limit on the uplink signal at 171 - 139 = -32 dbc. > > If the noise on your transmitted signal is 32 db down, you will degrade the > SNR at the sat by > 3 db. ( = they add as power not voltage). > > You will need to do some research with Mr Google to come up with the real > numbers to plug > into the calculations. They are different for each system design ( your > antenna, your erp ?.). > > Bob > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
