[Elecraft] Externmal ATU

[Phil & Debbie Salas]

"...MFJ released a new Firmware for the MFJ-998 dated 08/02/2010. ..."

The MFJ-998 wasn't interrupting the amp-key line when it tuned from memory. 
I guess it was assumed that this happend very quickly so this would not 
cause a problem.  However, as the relays operate you can have a momentary 
high VSWR condition.  So this will help.  HOWEVER - it takes a finite period 
of time for the tuner to "decide" that the VSWR is high and to measure the 
incoming frequency.  So during this "decision" process (when you change 
bands or antennas), you could have a high VSWR presented to the amplifier 
before the amp-enable line is interrupted and the new tuner values are 
snapped in place.   There are four ways around this:

1) With the tuner in full auto, flip the amp to standby and hit TUNE on the 
K3 when you change bands/antennas.  If the VSWR is greater than the MFJ-998 
programmed "start tuning" value, the tuner will tune.  Then flip the amp to 
operate.  This is what I do now (K3 tune output set for 15 watts).
2) Provide band data to the tuner so it tracks band changes before you even 
transmit.  Not supported by the current MFJ-998.  And this requires more 
untelligence if you have more than one antenna/band.
3) Leave the tuner in manual mode and press TUNE on the tuner when you 
change bands or antennas.  This interrupts the amp-key line before tuning 
starts.  But this requires a TUNE REQUEST input to the K3 which is not 
available.
4) Use resonant antennas on all bands and forget the tuner!

Phil - AD5X