The RF Applications cw watt meter has a similar function.

There have also been a few circuits in qst which will work the same way when 
connected across an analog swr meter that is set in the forward mode.

I bet there are a few similar circuits floating around the UK as well.

Ask around among the old time hams, especially if you know any blind people 
who have been in the hobby for a long time.

Of course, John's comment about having the comparitor connected across the 
meter of the radio is the best way to go. Once you get it calibrated with a 
bit of sighted help, you know exactly what the plate and grid readings are.

Tuning only for maximum power out may not keep the grids of the 6146 finals 
happy.

The grid is the most fragile part of the otherwise rugged 6146.



Mike Duke, K5XU
American Council of Blind Radio Amateurs