>"If the transceiver has a key out line that is activated a few ms before RF
is output, then that can operate the t/r circuitry in the amplifier,
including bias switching."
Agreed Vic, although in semi-BK-in and PTT voice modes, we then have
constant idle Ip that doesn't cut off until the rig's amp key line releases.
The small increase in heat dissipation seems to be a big issue for some
folks, not so much for others.
Alpha has been very focused on 3-stage EBS going back to their original
circuit in the ALPHA SEVENTY series. The 9500 is just as symptomatic. Same
with my Alpha 77Dx, 70A, and 70V. These amps switch into the final EBS
state only upon sensing input RF at ~ 100 mW. Fortunately, the 77Dx has a
bias idle pot to allow 0-150 mA of Ip when the key line is closed.
I see zero EBS artifact issues with my 87A. Perhaps the microcontroller
does a better job of EBS management.
Paul, W9AC
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