From: peterwieck33@gmail.com   
      
   > I've suggested possible RFI issues somehow causing the issue, but this    
   > is just a guess. I'm just as perplexed as he is.    
      
   I am going to offer a solution based on an audio model as it seems to cover   
   both your conditions. But, first, let me reframe the conditions and results to   
   make sure I am understanding it correctly.   
      
   Condition A:  When he modulates rF into an rF amplifier at a low level, all is   
   well.    
      
   Condition B: When he modulates rF into an rF amplifier at full output, he   
   either blows the fuse (solid-state amp), or fries the output tubes (tube amp):   
      
   If that is a correct understanding here is a potential diagnosis - and   
   suggestion:   
      
   Under Condition A, the secondary amplifier is not modulating anywhere near 500   
   watts. And so is not under any stress. Just as I have a 250wpc stereo amp at   
   home being fed from a pre-amp with roughly 2 volt maximum output, but running,   
   typically, at about    
   0.02 watts. Peak-to-average in this case is 20 dB. The power-amp may run the   
   very rare 200-watt peak, but most of the time it is running at far less.    
      
   Under Condition B, the system is modulating at the "FULL" 500 watts. Were my   
   power-amp to modulate at its maximum outlet, even briefly (more than a few   
   seconds), it would be pulling very nearly 30 amps at the wallplate - i.e.:   
   Blowing fuses. My 75wpc    
   tube amp would handle it somewhat better, but were it to be expected to do it   
   for over those few seconds, it would red-plate the tubes in short order. Given   
   its class, what it draws at full output and quiescent is not substantially   
   different - lots of    
   waste in tube designs, all those filaments, so it would red-plate before   
   blowing a fuse - they exist to protect the transformers.    
      
   So, I think your friend has a fundamental misunderstanding (if my contentions   
   and interpretations are correct) on how amplifiers work. They have a rating -   
   which is what they can deliver cleanly for some period of time at a certain   
   input level. But they    
   are not (usually) designed to operate at full peak modulation, all the time.    
      
   Peter Wieck   
   Melrose Park, PA   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)