开云体育

Here's some thread from 2016:
? ?/g/BITX20/topic/4105252

Farhan says it is a decoupling resistor for a driver stage.
So R144 and C142 do the same job for T6 as R135 and C133 are doing for T5 in the previous stage,
keep power supply noise from getting into that amplifier (and vise versa).

Note that R144 is 2.2 ohms, not 2.2k. ?The 2n2219a sees quite a bit of collector current.

U3 pin 3 just has a connection to the TX 12v rail, there is no cap local to U3 shown in the schematic.
Though not a bad idea to put one there.

You might consider building the newer uBitx PA instead:
? ??
Farhan is still working on a minimal set of uBitx LPF's that meet FCC specs for undesired emissions.
LIkewise, the Bitx PA should probably have Don Cantrell's second harmonic fix: ?
? ??


Jerry, KE7ER