In the R-23, that resistor amounts to 330 K. In the R-26, it is two 51K resistors in series, R-16 and R17, for a total of 102 Kohms. I am not sure how much one could reduce this value since it is connected directly to the 250 VDC B+.and it is shorted to ground to turn the BFO off. Ken W7EKB