After reading this tread I'd like to point out a few things I've seen. First, I think the 8877 gets a bad rap. Sure it has a fragile grid but the peak emissions that oxide coated cathode provides are amazing. With just an optocoupler watching the grid I was able to hold 7KW on the Bird from a single 8877.
I was trying to see what the tube could take and planed on blowing it up. Sounds crazy but I had a supply of surplus plasma RF generators that ran the tube donated to me as scrap. I didn't mind hooking one up to a 10 KVA pole pig to find the limits.
I thought the tube would blow up that day. To my surprise it handled over 7000 volts on the plate and stayed together being used several times a week for a year! One day it finally killed the tube and when I took the tube out it was blue in color from the extreme heat.
The grid was running well over 100 ma and the plate dissipation was far exceeded. Very bad practice for amplifier building but it sure was an enlightening test that revealed unexpected capabilities with the "fragile" 8877.
On the topic of 50 KW mobiles, they do exist on 11 meters. It is true their outputs do not reach the proper peaks to reproduce true AM. That would take 200 KW peak. More important is the RF exposure levels to the operator and those around. This is a very serious risk at these power levels and you are fooling yourself if you think you've come up with any safe way to transmit 50 KW with an antenna that has a center of radiation at essentially ground level.
The lucky ones have had the chance to connect headaches or blurred vision to the RF exposure and stopped. Not everyone will have the early warnings. Most have no clue how many times over the safe limits this RF exposure is.
I have nothing against 11 meter operators and have had some good fun on that band too. Hams are not going to convince 11 meter operators that their amps are better for many reasons. The main reason is the dollar to watt ratio and the fact ham amps are often not big enough
1.5 KW PEP is little more then a driver on this band today.
It's way too hard to convince someone who owns a working Wizard that the amp has serious design flaws. The mind set of "it works so it must be right" is difficult to erase. That's why those who know how to build quality 11 meter amps seem to be absent in the marketplace. They gave up on trying to find customers who knew the difference and were willing to pay for it.
Looking at Wizards site today I noticed he still uses copper strap to feed B+ to the tubes where there is no skin effect but continues to use simple wire to tie the anode to the PI network where the skin effect would benefit from copper strap. If that doesn't say "I have no clue about how RF works" I dunno what does. Almost seems like he makes an effort to get as much RF into the power supplies as possible.