[Johnson] 250-39 TR switch.

[Rodger]

I am in complete agreement with the problems Roy explained and another 
concern is that although theoretically most of these vacuum tube T/R 
switches are rated for pretty high power that is only true when the 
antenna is well matched to the transmission line, that is low SWR.  
Otherwise the voltage the T/R tube sees may be much higher than it can 
handle and then your receiver input is no longer isolated from the 
transmitter so prepare for smoke and follow-up repairs.  If you want to 
experience full break in CW like it existed in days past and are willing 
to put up with the drawbacks then you might want to play with one.  But 
otherwise a relay is going to be a better choice.

Rodger WQ9E