I should not post here due causing trouble with my posts. But, one more post. I seen many modifications to the popular Johnson Ranger transmitter. One of the best IMO is W8JI. He states the transmitter is well designed and perhaps Johnsons best design. He recommends the 500pF cap at the 12AX7 pin 7 to pin 1 be replaced with a .01uF for lower frequency response. That is about it. One item I noticed and have not found any reference to is the 12AU7 modulator driver tube. Looking at the plate curves it is poor (non-linear) and especially so at 310 volts plate. Here is the plate curves of the 12AU7 at 310 volts plate. As the tube output swings to less than 5 ma, it is not linear. The steps in-between the bias points should be close to equal. The tube looks a lot better at 150 volts plate. Now, lets look at the 6CG7 plate curves at 310 volts plate. It is much more linear. I recommend replacing the 12AU7 with a 6CG7. The 12AU7 and 6CG7 is almost identical in operation, ie bias points, plate resistance, etc. To use in the Johnson Ranger simply cut the jumper on pins 4 & 5. Then, remove the two filament wires from pin 9 and move to either pin 4 or 5 that is not grounded to the chassis. Either pin could be grounded, on my Johnson pin 5 was grounded, The 6CG7 used .6 amps filament and the 12AU7 uses .3 amps. The extra filament draw will not cause harm to the transformer. If you have concern, you can replace the 6AX5 with a solid-state rectifier freeing up more current than the 6CG7 draws. I do not mind the 6AX5 solid-state mods as only an extra 20 volts is on the low B+. I do not like the 5R4 solid-state replacement as about 50 extra volts is supplied. Other have used solid-state replacing the 5R4 and have had no issues that I read. Will the Ranger sound better? It may with a strong signal, but not likely noticeable during weak signals due to band noise. Changing the 12Au7 to a 6CG7 is not for everyone, but I thought it is interesting.