Satellite LNBs: The awkward


Many of the current generation of LNBs fit into the 'awkward' category. More effort in minimising material and production costs inevitable result in items more difficult to modify, but just think of it as a challenge.

All the items in this section have been modified for use as receive-antennas-with-integral-preamp. Assume a pre-amp gain of 20dB just as per older models, but expect a slightly better noise figure.

With these LNBs , it is not possible to connect to the output of the final RF amplifier via a hole through the pcb, so an alternative has to be found. Routing a semi-rigid RG 405 feed over the component side is usually possible by adding a groundplane over the (unused) band-pass filter. Thin sticky-backed copper tape is good for this. If it is thin enough, it can be allowed to be slightly oversized so that the sectionised screen securely clamps it into possition after re-assemby. If the area of the ground plane is big enough, it doesn't even have to be dc grounded - the reactance to ground will be low enough. In any case, the semi-rigid cable will be clamped by the outer casting shell, on final re-assembly. A notch will have to be filed in the casting to avoid the cable being completely compressed as the assembly screws are tightened.

Cambridge G88

Unmodified G88 unit