<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div> </div><div>> Has anyone else tried driving an Ameritron AL-811 amplifier using the<br>> PennyWhistle amplifier? I have ruined 6 power MOS FETs trying to do this.<br>><br>> It's weird because my SoftRock can drive my AL-811 to 30 Watts by itself<br>> without damage but as soon as I try the PennyWhistle I blow out its FETs.<br>><br>> Has anyone else had this problem -- and if so what changes did you make to<br>> the AL-811 or PennyWhistle to stop this from happening?<br>><br>> Mike N9MS</div><div><br> </div><div>Hi Mike - the schematic of the AL-811 shows that the input relay is open-circuited</div><div>during the brief few-milliseconds time that it takes to switch from receive to transmit.</div><div>If your Pennywhistle were putting out RF during those few milliseconds, it would be into
an</div><div>open circuit.</div><div> </div><div>I don't find any RF protection circuitry on the output of the Pennywhistle schematic;</div><div>thus don't know whether it can or cannot handle operation into an open circuit without failure.</div><div> </div><div>-- Tom, N5EG</div><div> </div></div></body></html>