Tacos Digest, Vol 102, Issue 8

[rabruner at aol.com]

The power is multiplexed over the coax from the satellite receiver.  You should be able to measure about +20 volts or so (there is a wide range of voltages used and it's not critical)  at the input F connector on the receiver and again at the antenna end of the coax.  Unlikely the coax has failed.  It's possible you've lost the power from the receiver to the antenna due to a failure in the receiver, but more likely the LNB is toast caused by some nearby lightening surge.  Consumer LNBs are not terribly expensive, you just have to get one with the right IF for your receiver and with the right feed setup -- one bird, two bird, for your system. 
    The LNB contains a local oscillator and mixer that converts the incoming signal from the satellite to an L-band IF frequency at a pretty high level.  The down mixing is what distinguishes the LNB (low noise block converter) from an LNA (Low Noise Amplifier).  LNAs are not commonly found on systems these days as they require that everything is handled on frequency which requires either that the receiver be at the dish, or that you have wave guide all the way to the radio.  LNBS are more less a frequent failure item -- they live in a harsh environment.  The wonder is that they don't fail more often than they do.
Bob Bruner
W9TAJ















>> When examining the LNB, I did not see any power wires, just the RF lines.  I have wondered, and do not understand how the LNB gets it's power.  Robert, anything you could say about this would help.


Best Wishes
Richard Demaret
KI4KXJ

                                   













 
 






 


  


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