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Aug 28th, 2008 at 5:18pm
Why does the DVB-S2 loose lock ? Does the noise level increase ? Is there interference ? Does the noise floor or carrier level change ? Does phase noise increase (increase in BER with no change in C/N) ? Is there a problem with the power supply to the DVB-S2 LNB or receiver ?
There must be some cause link from the TX1 to the DVB-S2 receiver. Unfortunately there are many possibilities. It could be very local, like the mains power for the TX1 is on the same mains supply at the DVB-S2 modem and the mains supply is not adequate when TX1 is powered on. More likely, it is some IF or RF interference problem.
Is there any chance of measuring and recording spectrum analyser plots of:
If there are 6 GHz couplers or low level monitor points on the HPA TX outputs (3 - 7 GHz), plus expanded views of the transmitted carriers and any spurious transmissions.
With and without TX1 powered on:
LNB outputs (DC to 7 GHz) or LNA outputs (3 - 7 GHz), plus expanded views of the wanted carriers. In the case of LNBs the range DC to 200kHz is of interest in case of switch mode PSUs causing phase noise.
If there are spare, exposed, ports on a splitter they should all be terminated with 50 or 75 ohm terminations.
Best regards, Eric.
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