[hpsdr] PennyWhistle driving an Ameritron AL-811

[Tom McDermott]

> Has anyone else tried driving an Ameritron AL-811 amplifier using the
> PennyWhistle amplifier? I have ruined 6 power MOS FETs trying to do this.
>
> It's weird because my SoftRock can drive my AL-811 to 30 Watts by itself
> without damage but as soon as I try the PennyWhistle I blow out its FETs.
>
> Has anyone else had this problem -- and if so what changes did you make to
> the AL-811 or PennyWhistle to stop this from happening?
>
> Mike N9MS

 
Hi Mike - the schematic of the AL-811 shows that the input relay is open-circuited
during the brief few-milliseconds time that it takes to switch from receive to transmit.
If your Pennywhistle were putting out RF during those few milliseconds, it would be into an
open circuit.
 
I don't find any RF protection circuitry on the output of the Pennywhistle schematic;
thus don't know whether it can or cannot handle operation into an open circuit without failure.
 
-- Tom, N5EG
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20130511/4901b881/attachment-0004.htm>