Easy LNB modifications

 

Some LNBs are inherantly easier to modify than others, but of-course, it still depends on the actual requirement as to whether or not a particular model falls into the category of 'easy to modify' - ie, only requiring holes to be drilled in the housing for access to added connectors.

All the LNBs in this category date back to the UK analogue satellite era (mid to late 1990s) - shaving every penny off the design hadn't quite been an LNB priority, it would seem, back then.

Antenna with built-in preamp modifications

 

Most LNBs have two stages of gain after the antenna(s), with the 1st stage being a switched pair of devices - one for horizontal polarisation and the other for vertical. Each stage will have a gain of about 10dB, or just over. The second stage feeds the mixer via an image filter.

In this application, the output is taken immediately after the 2nd stage, prior to the filter. The track is cut to isolate the filter, and further cut to add in a 2p2 blocking capacitor. A 0.8mm hole is drilled through both the pcb and the housing. An SMA socket is then sweated to the groundplane side of the board, and the hole in the housing opened up to allow the connector to poke through. That's all there is to it! - it is not necessary to modify the antenna probe for the slightly lower 10 GHz band. Sensitivity will still be good enough to notice a pronounced increase in noise level as the LNB is pointed down to the ground from looking upat clear sky.

 

 

 

 

Example 1: Amstrad SLB1

pcb groundplane side

 
pcb component side

 

 

Example 2: Cambridge AE12

 

 

pcb groundplane side

 

 

pcb component side

 

 

Example 3: Grundig AEN1S

 

 

pcb component side

 

 

 

It is interesting to note that the pcb is identicle to that used in the Amstrad SLB1!

Presumeably, the Amstrad part was actually manufactured by Grundig, though being early 1990s boards, it is now really only of historic interest....