Contacts.cfg - Display Range To Opportunity Radio Contacts
 

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Should I set this to zero if I don't want to see those black boxes appearing on the map?

I think so, for both contacts' range. It probably would be like removing radio room or bending radio antenna off. I am not sure how it would function with zero, usually I put 1 at most minimum for other settings just to be safe since there are not or not enough tutorials about changing layouts in game by changing cfg settings with handful of bugs still existing.

Any real low number will do
Never tried 0 but 1 is a good compromise
You should see a ship before then anyway unless in thick fog

Yep, setting both Display Range To Opportunity Radio Contacts and Display Range To Important Radio Contacts to 1 works fine - no more black boxes appearing. Thanks guys, yet another mystery solved!