Linkstar Modem : flashing LED ?

Just some questions to think about and some ideas.. Not sure about this...

Is it slow flashing or fast flashing ?  Does is stay the same flashing for a long time ?  Does it eventually go solid green (normal) ?.  Long time at fast flashing might be hub problem.   Does the SAT LED go off indicating loss of the outlink carrier ?   What is the QPSK BER before, during, after ? 

How do you reboot the modem ?  Do you cycle the power or type in a command ?  If you type in a command to get it back to normal you may have a hardware memory fault.

Does is always come up working normally after cycling the power ?

When you changed the LNB did the problem continue to occur ?  Sometimes the local oscillator in the LNB stops and cycling the power will restart it.  Often temperature related or sun angle on to the LNB.

Have you checked both ends of the LNB cable ?  The centre pin must be long enough and clean.  The outer braid sheath must connect to the plud outer shell at each end.

Is the power supply connected to the main circuit board with soldered wires or with a multiway plug?.  If it is a multiway plug, power everything off.  Earth your body to the chassis to avoid static electricity damage, and then unplug the plug and reinsert 5 times to clean the pins and spring contacts. Slightly low Vcc volts might cause such symptoms, due to slight corrosion on the plug contacts. 

Best regards, Eric.

I suggest you contact your hub and ask them to investigate why your site is having outages and is very slow to finally lock up after a power cycle.

It could be that your transmit carrier has poor quality at the hub.

I wonder if you could peak up your pointing to improve your receive QPSK BER.  Your present BER 0.00088 is satisfactory (but not good 0.0001, or excellent 0.00005 or less).  Your 0.00088 is quite feasible if your antenna is not well pointed and the satellite outlink carrier power rather high.  

Having an excessively high power outlink carrier makes it very easy for customers to find the satellite but makes it very difficult for them to comprehend that they still need to spend a lot more time peaking up properly to get the transmit pointing correct.

It really matters to get to the exact centre as the transmit beam is narrower then the receive beam, so you can have a perfectly satisfactory receive signal and still have a poor transmit signal.

It is no good the hub increasing your transmit power to try and compensate for your mispointing.  It will probably overload your BUC and cause signal distortion and poor signal quality into the hub.

I would get the hub to test your site using a CW carrier to check the P-1dB compression point and the quality of your bursts into the hub when the BUC power is at the P-1dB operating point. Then set the correct level.

Swapping the cables might identify if one cable has much more loss than the other.  Could the transmit cable be corroded internally with water ?  The transmit cable is very sensitive to losses as this directly affects the transmit signal.   The LNB cable loss may vary over a wide range (wanted signal level -30 dBm to -70 dBm, -50dBm typical) and the modem will compensate using automatic receive gain control,

Best regards, Eric.