Re: Killed TX this time...


Evan Hand
 

Peter,
The readings for Q90 do look suspect.  I would suggest removing it as a starting point, then measure the resistors again.  Q90 has been know to fail, mostly from nearby transmitters when the uBITX is connected to an antenna.  I have not heard or read of it going out because of low or high SWR on TX.  Back to Back 1n914 or 1n4148 diodes across K1 pins 12 and 16 can protect the BE junction of Q90 when not transmitting.  The threshold voltage of the diodes is high enough that it will not affect receiver sensitivity yet still protect Q90.  Alternative is to make sure that the antenna is disconnected or grounded when using other transmitters nearby to it.

Just my thoughts,
73
Evan
AC9TU

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