[mr_toad]

> If there was anything like a high power transistor back then he would have used that.

Mercury arc rectifiers were used long before his death.

[crote]

Yes, but a rectifier only rectifies. That's not going to give you DC-DC conversion - let alone converting it to a higher voltage for long-distance transmission.

[wildzzz]

DC-DC before the transistor was difficult to do at scale. Vibrators and relays existed but were not reliable long term.