[Elecraft] Why R88, R89 and R90 ?

[Roland]

Hello all, i've a little question,

In manual appendix-B RF-Board sheet 2 of 4 right-upper corner, just under
noise-blanker you find R88, R89 and R90. just under these resistors is
written -5dB, Z=150 ohm.
What is the purpose of these resistors ?

Because, when  removing the KNB2 and put a jumper in connector J12 at
pin1-6, the signal is much stronger and louder !!! It increased with 3
S-points and thats a lot, I guess.
(on rf-board after placing KNB2:  R88=2K7, R89=0, R90=empty).
Any ideas ?

73, Roland
PE1PHU - K2#3195