A pair of 811's, eh? What's the plate voltage? Grid or cathode driven (grounded-grid)? In any case, a pair will deliver about ~400W carrier or so, at full drive. In AM operation, you should see about ~100 W more or less, (dead key). I would never use an 811 type amp for AM - too underpowered.Lol, Mono band Amp, Ten only.
73
jeff