Which install manual are you looking at, this is from the 650 TSO manual:
"If RG-142B or RG-400 is used, 1.5 dB equates to a length of approximately 6.5 feet of
cable with a connector on each end. RG-142B or RG-400 cable can be used as long as the
length is less than 35 feet. For longer lengths, use low-loss double or triple shielded 50
coax."
"For very short runs, where the loss is less than 1.5 dB, additional cable should be used to increase
the loss to within 1.5 dB to 6.5 dB. This additional cable may be coiled, taking into account the minimum bend
radius of the cable."