Sky q lnb stripdown

[Channel Hopper]

For anyone that is interested.

MaxLinear chip on board, crystal frequency 50.08Mhz

https://www.maxlinear.com/pb/mxl801_mxl802_mxl803_pb.pdf

 

[s-band]

Nice pics. The EL021s I bought on Amazon a couple of years ago looked new but had intermittent shorts to ground in the region of the blue inductors (bottom right pic 8.JPG). I guess that they were installers' rejects. If the inductor is mis-placed and/or the lid is slightly mis-aligned, the lid touches the supply track. If you get one that has a DC short on the output(s), it's easy enough to fix.

 

[jeallen01]

The through-holes in the main tracks are "interesting": ventilation? RF emissions suppression? RF susceptibility suppression??, or "what"????

 

[Terryl]

The through-holes in the main tracks are "interesting": ventilation? RF emissions suppression? RF susceptibility suppression??, or "what"????

The through holes go to more circuit traces under the PCB,(copper plated) on the ground side it gives you more overall ground plane to work with, on the signal side it gives you more to play with as far as tuning the circuit for pass and reject filtering, also tweaking the SWR on some of the high end RF signals to/from the mixer stages, some you see are just copper traces that look like they would do nothing, (see photo #7) these act like filter components to knock down spurs and harmonics in the LO and IF signals.

Prototyping a board like this was a headache, at some stage it looked like a bunch of chopped up copper foil, haphazerdly placed here and there, but after a bit of work it gets the job done, trying to get it into production took a bit.

 

[jeallen01]

Thanks, it was just that I had never seen so many unused through-holes, and in such fairly regular arrangements! (and I am aware of using track lengths/widths for frequency tuning/filtering - bit of a variantion in the "oldish" technique of stub-tuning which I've occasionally used myself far in the past!)

 

[MarsBar]

Good pictures! Tear downs are allways interesting. If you find old LNB's single band it would be nice to see the development over the years, I remember they all had single transistors and a LM7808 power regulator.