[AMRadio] Ongoing Quest: Legal Limit AM Amp

[Ross Stenberg]

Bernie took the time to write a nice synopsis of the AM linear 
situation. I would like to ad my simple rule of thumb that has never let 
me down with a variety of commercial amps run  AM mode. Run no more 
carrier level than what amounts to 25% of their rated PEP output. The 
math behind 375 watts of fully modulated carrier equals 1500 watts PEP 
does not lie. Many of the common older amps could really only safely 
output 600 to 800 watts PEP which would be a 150 to 200 watt AM carrier. 
I used to run a Ameritron AL-82 easily at full legal AM limit. That amp, 
which uses a pair of 3-500's run at 3800 volts or so with a very hefty 
power transformer, could just as easily run 1500 watts PEP output all 
day long. The same amp chassis was also available with higher rated 
3CX-1200 or 8877 output tube. On the other hand the venerable SB-200 
would only be good for about a 150+ watt carrier. With most common 
grounded grid amps I still had to reduce the power of my Ranger II to 
about 20-25 watts for proper drive levels by lowering the screen voltage..

         73 Ross K9COX