Theoretically, the lowest noise figure obtainable from any device is limited by any components in the signal chain with the highest thermal noise. The first component in the chain would be the detector circuit and on a Universal LNB, this would be a pin diode. At Ku band, the detectors are rated at manufacture to about 40K which converts to a figure of 0.5 dB. Presently the LNB market is active by those selling what appears to be an extraordinarily good device, some use the best of the component batch – and end up with good performance overall (rare). Some modify existing LNBs by the use of fancy smoothing circuits to eliminate any further incoming noise from the power supply – there are definite improvements when used with cheaper receivers, especially those with switch mode supplies.

The LNB sets the noise floor for your entire satellite receiving system. Less noise here means that more signal will actually arrive at the receiver. Today’s high-performance LNBs use Gallium Arsenide (GaAs) semiconductor and High Electron Mobility Transistor (HEMT) technologies to minimize the noise level of the LNB. Note even the best LNB will only marginally improve reception, the only way to significantly improve reception (Gain), is to use a larger dish.

Read more about LNB specification