I have been running the LNB IF over the supplied 75R ‘white’ cable. This is not quite long enough to reach to the selected position of the Minitoiuner. On the other the 25MHz reference runs over a much longer RG58 cable, but only to the rack position of the Leo Bodnar Mini GPS source.
In order to close the shack door and generally tidy up the cable runs, the cables have now been brought into the shack through the wall gland cable entry. Because of the incompatible cable lengths decided to swap over the functions of the two cables. The shorter 75 R IF cable now being used for the 25MHz reference and the longer RG58 now the IF and LNB power cable.
Although the Minitoiune display showed a strong signal, it was clear from the phase constellation that the software was struggling to obtain lock. I couldn’t get a picture from Freesat.
Swap the cables back, temporarily, and all was well again.
With the high gain of the LNB the Minitoiuner should be OK with the much longer IF lead. I changed the reference drive level over quite a large range with no success, just in case.
Could the reference be objecting to 75R cable or was something else happening? I decided to reset the 25MHz reference drive level and use another 50R coax cable reference able connection to the LNB. This worked absolutely fine.
I really am not sure whether the problem was down to impedance or to cable loss (at 25MHz?). However, I will replace the crappy white 75R stuff with a length of RG58 tomorrow and see if all is still OK.
Entertaining times!
Sam
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